+Lua 5.4 Reference Manual
+
+Lua 5.4 Reference Manual
+
+The reference manual is the official definition of the Lua language.
+
+For a complete introduction to Lua programming, see the book
+Programming in Lua.
+
+
+ +Copyright © 2020–2025 Lua.org, PUC-Rio. +Freely available under the terms of the +Lua license. + + +
+Lua 5.4 Reference Manual
++by Roberto Ierusalimschy, Luiz Henrique de Figueiredo, Waldemar Celes + +
+ +Copyright © 2020–2025 Lua.org, PUC-Rio. +Freely available under the terms of the +Lua license. + + +
+ + ++ + + + + + +
+Lua is a powerful, efficient, lightweight, embeddable scripting language. +It supports procedural programming, +object-oriented programming, functional programming, +data-driven programming, and data description. + + +
+Lua combines simple procedural syntax with powerful data description +constructs based on associative arrays and extensible semantics. +Lua is dynamically typed, +runs by interpreting bytecode with a register-based +virtual machine, +and has automatic memory management with +a generational garbage collection, +making it ideal for configuration, scripting, +and rapid prototyping. + + +
+Lua is implemented as a library, written in clean C,
+the common subset of standard C and C++.
+The Lua distribution includes a host program called lua,
+which uses the Lua library to offer a complete,
+standalone Lua interpreter,
+for interactive or batch use.
+Lua is intended to be used both as a powerful, lightweight,
+embeddable scripting language for any program that needs one,
+and as a powerful but lightweight and efficient stand-alone language.
+
+
+
+As an extension language, Lua has no notion of a "main" program:
+it works embedded in a host client,
+called the embedding program or simply the host.
+(Frequently, this host is the stand-alone lua program.)
+The host program can invoke functions to execute a piece of Lua code,
+can write and read Lua variables,
+and can register C functions to be called by Lua code.
+Through the use of C functions, Lua can be augmented to cope with
+a wide range of different domains,
+thus creating customized programming languages sharing a syntactical framework.
+
+
+
+Lua is free software,
+and is provided as usual with no guarantees,
+as stated in its license.
+The implementation described in this manual is available
+at Lua's official web site, www.lua.org.
+
+
+
+Like any other reference manual, +this document is dry in places. +For a discussion of the decisions behind the design of Lua, +see the technical papers available at Lua's web site. +For a detailed introduction to programming in Lua, +see Roberto's book, Programming in Lua. + + + +
+This section describes the basic concepts of the language. + + + + + +
+Lua is a dynamically typed language. +This means that +variables do not have types; only values do. +There are no type definitions in the language. +All values carry their own type. + + +
+All values in Lua are first-class values. +This means that all values can be stored in variables, +passed as arguments to other functions, and returned as results. + + +
+There are eight basic types in Lua: +nil, boolean, number, +string, function, userdata, +thread, and table. +The type nil has one single value, nil, +whose main property is to be different from any other value; +it often represents the absence of a useful value. +The type boolean has two values, false and true. +Both nil and false make a condition false; +they are collectively called false values. +Any other value makes a condition true. +Despite its name, +false is frequently used as an alternative to nil, +with the key difference that false behaves +like a regular value in a table, +while a nil in a table represents an absent key. + + +
+The type number represents both
+integer numbers and real (floating-point) numbers,
+using two subtypes: integer and float.
+Standard Lua uses 64-bit integers and double-precision (64-bit) floats,
+but you can also compile Lua so that it
+uses 32-bit integers and/or single-precision (32-bit) floats.
+The option with 32 bits for both integers and floats
+is particularly attractive
+for small machines and embedded systems.
+(See macro LUA_32BITS in file luaconf.h.)
+
+
+
+Unless stated otherwise, +any overflow when manipulating integer values wrap around, +according to the usual rules of two-complement arithmetic. +(In other words, +the actual result is the unique representable integer +that is equal modulo 2n to the mathematical result, +where n is the number of bits of the integer type.) + + +
+Lua has explicit rules about when each subtype is used, +but it also converts between them automatically as needed (see §3.4.3). +Therefore, +the programmer may choose to mostly ignore the difference +between integers and floats +or to assume complete control over the representation of each number. + + +
+The type string represents immutable sequences of bytes.
+
+Lua is 8-bit clean:
+strings can contain any 8-bit value,
+including embedded zeros ('\0').
+Lua is also encoding-agnostic;
+it makes no assumptions about the contents of a string.
+The length of any string in Lua must fit in a Lua integer.
+
+
+
+Lua can call (and manipulate) functions written in Lua and +functions written in C (see §3.4.10). +Both are represented by the type function. + + +
+The type userdata is provided to allow arbitrary C data to +be stored in Lua variables. +A userdata value represents a block of raw memory. +There are two kinds of userdata: +full userdata, +which is an object with a block of memory managed by Lua, +and light userdata, +which is simply a C pointer value. +Userdata has no predefined operations in Lua, +except assignment and identity test. +By using metatables, +the programmer can define operations for full userdata values +(see §2.4). +Userdata values cannot be created or modified in Lua, +only through the C API. +This guarantees the integrity of data owned by +the host program and C libraries. + + +
+The type thread represents independent threads of execution +and it is used to implement coroutines (see §2.6). +Lua threads are not related to operating-system threads. +Lua supports coroutines on all systems, +even those that do not support threads natively. + + +
+The type table implements associative arrays,
+that is, arrays that can have as indices not only numbers,
+but any Lua value except nil and NaN.
+(Not a Number is a special floating-point value
+used by the IEEE 754 standard to represent
+undefined numerical results, such as 0/0.)
+Tables can be heterogeneous;
+that is, they can contain values of all types (except nil).
+Any key associated to the value nil is not considered part of the table.
+Conversely, any key that is not part of a table has
+an associated value nil.
+
+
+
+Tables are the sole data-structuring mechanism in Lua;
+they can be used to represent ordinary arrays, lists,
+symbol tables, sets, records, graphs, trees, etc.
+To represent records, Lua uses the field name as an index.
+The language supports this representation by
+providing a.name as syntactic sugar for a["name"].
+There are several convenient ways to create tables in Lua
+(see §3.4.9).
+
+
+
+Like indices, +the values of table fields can be of any type. +In particular, +because functions are first-class values, +table fields can contain functions. +Thus tables can also carry methods (see §3.4.11). + + +
+The indexing of tables follows
+the definition of raw equality in the language.
+The expressions a[i] and a[j]
+denote the same table element
+if and only if i and j are raw equal
+(that is, equal without metamethods).
+In particular, floats with integral values
+are equal to their respective integers
+(e.g., 1.0 == 1).
+To avoid ambiguities,
+any float used as a key that is equal to an integer
+is converted to that integer.
+For instance, if you write a[2.0] = true,
+the actual key inserted into the table will be the integer 2.
+
+
+
+Tables, functions, threads, and (full) userdata values are objects: +variables do not actually contain these values, +only references to them. +Assignment, parameter passing, and function returns +always manipulate references to such values; +these operations do not imply any kind of copy. + + +
+The library function type returns a string describing the type
+of a given value (see type).
+
+
+
+
+
+
+As we will discuss further in §3.2 and §3.3.3,
+any reference to a free name
+(that is, a name not bound to any declaration) var
+is syntactically translated to _ENV.var.
+Moreover, every chunk is compiled in the scope of
+an external local variable named _ENV (see §3.3.2),
+so _ENV itself is never a free name in a chunk.
+
+
+
+Despite the existence of this external _ENV variable and
+the translation of free names,
+_ENV is a completely regular name.
+In particular,
+you can define new variables and parameters with that name.
+Each reference to a free name uses the _ENV that is
+visible at that point in the program,
+following the usual visibility rules of Lua (see §3.5).
+
+
+
+Any table used as the value of _ENV is called an environment.
+
+
+
+Lua keeps a distinguished environment called the global environment.
+This value is kept at a special index in the C registry (see §4.3).
+In Lua, the global variable _G is initialized with this same value.
+(_G is never used internally,
+so changing its value will affect only your own code.)
+
+
+
+When Lua loads a chunk,
+the default value for its _ENV variable
+is the global environment (see load).
+Therefore, by default,
+free names in Lua code refer to entries in the global environment
+and, therefore, they are also called global variables.
+Moreover, all standard libraries are loaded in the global environment
+and some functions there operate on that environment.
+You can use load (or loadfile)
+to load a chunk with a different environment.
+(In C, you have to load the chunk and then change the value
+of its first upvalue; see lua_setupvalue.)
+
+
+
+
+
+
+Several operations in Lua can raise an error. +An error interrupts the normal flow of the program, +which can continue by catching the error. + + +
+Lua code can explicitly raise an error by calling the
+error function.
+(This function never returns.)
+
+
+
+To catch errors in Lua,
+you can do a protected call,
+using pcall (or xpcall).
+The function pcall calls a given function in protected mode.
+Any error while running the function stops its execution,
+and control returns immediately to pcall,
+which returns a status code.
+
+
+
+Because Lua is an embedded extension language,
+Lua code starts running by a call
+from C code in the host program.
+(When you use Lua standalone,
+the lua application is the host program.)
+Usually, this call is protected;
+so, when an otherwise unprotected error occurs during
+the compilation or execution of a Lua chunk,
+control returns to the host,
+which can take appropriate measures,
+such as printing an error message.
+
+
+
+Whenever there is an error, +an error object +is propagated with information about the error. +Lua itself only generates errors whose error object is a string, +but programs can generate errors with +any value as the error object. +It is up to the Lua program or its host to handle such error objects. +For historical reasons, +an error object is often called an error message, +even though it does not have to be a string. + + +
+When you use xpcall (or lua_pcall, in C)
+you can give a message handler
+to be called in case of errors.
+This function is called with the original error object
+and returns a new error object.
+It is called before the error unwinds the stack,
+so that it can gather more information about the error,
+for instance by inspecting the stack and creating a stack traceback.
+This message handler is still protected by the protected call;
+so, an error inside the message handler
+will call the message handler again.
+If this loop goes on for too long,
+Lua breaks it and returns an appropriate message.
+The message handler is called only for regular runtime errors.
+It is not called for memory-allocation errors
+nor for errors while running finalizers or other message handlers.
+
+
+
+Lua also offers a system of warnings (see warn).
+Unlike errors, warnings do not interfere
+in any way with program execution.
+They typically only generate a message to the user,
+although this behavior can be adapted from C (see lua_setwarnf).
+
+
+
+
+
+
+Every value in Lua can have a metatable.
+This metatable is an ordinary Lua table
+that defines the behavior of the original value
+under certain events.
+You can change several aspects of the behavior
+of a value by setting specific fields in its metatable.
+For instance, when a non-numeric value is the operand of an addition,
+Lua checks for a function in the field __add of the value's metatable.
+If it finds one,
+Lua calls this function to perform the addition.
+
+
+
+The key for each event in a metatable is a string
+with the event name prefixed by two underscores;
+the corresponding value is called a metavalue.
+For most events, the metavalue must be a function,
+which is then called a metamethod.
+In the previous example, the key is the string "__add"
+and the metamethod is the function that performs the addition.
+Unless stated otherwise,
+a metamethod can in fact be any callable value,
+which is either a function or a value with a __call metamethod.
+
+
+
+You can query the metatable of any value
+using the getmetatable function.
+Lua queries metamethods in metatables using a raw access (see rawget).
+
+
+
+You can replace the metatable of tables
+using the setmetatable function.
+You cannot change the metatable of other types from Lua code,
+except by using the debug library (§6.10).
+
+
+
+Tables and full userdata have individual metatables, +although multiple tables and userdata can share their metatables. +Values of all other types share one single metatable per type; +that is, there is one single metatable for all numbers, +one for all strings, etc. +By default, a value has no metatable, +but the string library sets a metatable for the string type (see §6.4). + + +
+A detailed list of operations controlled by metatables is given next. +Each event is identified by its corresponding key. +By convention, all metatable keys used by Lua are composed by +two underscores followed by lowercase Latin letters. + + + +
__add:
+the addition (+) operation.
+If any operand for an addition is not a number,
+Lua will try to call a metamethod.
+It starts by checking the first operand (even if it is a number);
+if that operand does not define a metamethod for __add,
+then Lua will check the second operand.
+If Lua can find a metamethod,
+it calls the metamethod with the two operands as arguments,
+and the result of the call
+(adjusted to one value)
+is the result of the operation.
+Otherwise, if no metamethod is found,
+Lua raises an error.
+__sub:
+the subtraction (-) operation.
+Behavior similar to the addition operation.
+__mul:
+the multiplication (*) operation.
+Behavior similar to the addition operation.
+__div:
+the division (/) operation.
+Behavior similar to the addition operation.
+__mod:
+the modulo (%) operation.
+Behavior similar to the addition operation.
+__pow:
+the exponentiation (^) operation.
+Behavior similar to the addition operation.
+__unm:
+the negation (unary -) operation.
+Behavior similar to the addition operation.
+__idiv:
+the floor division (//) operation.
+Behavior similar to the addition operation.
+__band:
+the bitwise AND (&) operation.
+Behavior similar to the addition operation,
+except that Lua will try a metamethod
+if any operand is neither an integer
+nor a float coercible to an integer (see §3.4.3).
+__bor:
+the bitwise OR (|) operation.
+Behavior similar to the bitwise AND operation.
+__bxor:
+the bitwise exclusive OR (binary ~) operation.
+Behavior similar to the bitwise AND operation.
+__bnot:
+the bitwise NOT (unary ~) operation.
+Behavior similar to the bitwise AND operation.
+__shl:
+the bitwise left shift (<<) operation.
+Behavior similar to the bitwise AND operation.
+__shr:
+the bitwise right shift (>>) operation.
+Behavior similar to the bitwise AND operation.
+__concat:
+the concatenation (..) operation.
+Behavior similar to the addition operation,
+except that Lua will try a metamethod
+if any operand is neither a string nor a number
+(which is always coercible to a string).
+__len:
+the length (#) operation.
+If the object is not a string,
+Lua will try its metamethod.
+If there is a metamethod,
+Lua calls it with the object as argument,
+and the result of the call
+(always adjusted to one value)
+is the result of the operation.
+If there is no metamethod but the object is a table,
+then Lua uses the table length operation (see §3.4.7).
+Otherwise, Lua raises an error.
+__eq:
+the equal (==) operation.
+Behavior similar to the addition operation,
+except that Lua will try a metamethod only when the values
+being compared are either both tables or both full userdata
+and they are not primitively equal.
+The result of the call is always converted to a boolean.
+__lt:
+the less than (<) operation.
+Behavior similar to the addition operation,
+except that Lua will try a metamethod only when the values
+being compared are neither both numbers nor both strings.
+Moreover, the result of the call is always converted to a boolean.
+__le:
+the less equal (<=) operation.
+Behavior similar to the less than operation.
+__index:
+The indexing access operation table[key].
+This event happens when table is not a table or
+when key is not present in table.
+The metavalue is looked up in the metatable of table.
+
+
+
+The metavalue for this event can be either a function, a table,
+or any value with an __index metavalue.
+If it is a function,
+it is called with table and key as arguments,
+and the result of the call
+(adjusted to one value)
+is the result of the operation.
+Otherwise,
+the final result is the result of indexing this metavalue with key.
+This indexing is regular, not raw,
+and therefore can trigger another __index metavalue.
+
__newindex:
+The indexing assignment table[key] = value.
+Like the index event,
+this event happens when table is not a table or
+when key is not present in table.
+The metavalue is looked up in the metatable of table.
+
+
+
+Like with indexing,
+the metavalue for this event can be either a function, a table,
+or any value with an __newindex metavalue.
+If it is a function,
+it is called with table, key, and value as arguments.
+Otherwise,
+Lua repeats the indexing assignment over this metavalue
+with the same key and value.
+This assignment is regular, not raw,
+and therefore can trigger another __newindex metavalue.
+
+
+
+Whenever a __newindex metavalue is invoked,
+Lua does not perform the primitive assignment.
+If needed,
+the metamethod itself can call rawset
+to do the assignment.
+
__call:
+The call operation func(args).
+This event happens when Lua tries to call a non-function value
+(that is, func is not a function).
+The metamethod is looked up in func.
+If present,
+the metamethod is called with func as its first argument,
+followed by the arguments of the original call (args).
+All results of the call
+are the results of the operation.
+This is the only metamethod that allows multiple results.
+
+In addition to the previous list,
+the interpreter also respects the following keys in metatables:
+__gc (see §2.5.3),
+__close (see §3.3.8),
+__mode (see §2.5.4),
+and __name.
+(The entry __name,
+when it contains a string,
+may be used by tostring and in error messages.)
+
+
+
+For the unary operators (negation, length, and bitwise NOT), +the metamethod is computed and called with a dummy second operand, +equal to the first one. +This extra operand is only to simplify Lua's internals +(by making these operators behave like a binary operation) +and may be removed in future versions. +For most uses this extra operand is irrelevant. + + +
+Because metatables are regular tables,
+they can contain arbitrary fields,
+not only the event names defined above.
+Some functions in the standard library
+(e.g., tostring)
+use other fields in metatables for their own purposes.
+
+
+
+It is a good practice to add all needed metamethods to a table
+before setting it as a metatable of some object.
+In particular, the __gc metamethod works only when this order
+is followed (see §2.5.3).
+It is also a good practice to set the metatable of an object
+right after its creation.
+
+
+
+
+
+
+Lua performs automatic memory management. +This means that +you do not have to worry about allocating memory for new objects +or freeing it when the objects are no longer needed. +Lua manages memory automatically by running +a garbage collector to collect all dead objects. +All memory used by Lua is subject to automatic management: +strings, tables, userdata, functions, threads, internal structures, etc. + + +
+An object is considered dead +as soon as the collector can be sure the object +will not be accessed again in the normal execution of the program. +("Normal execution" here excludes finalizers, +which can resurrect dead objects (see §2.5.3), +and excludes also operations using the debug library.) +Note that the time when the collector can be sure that an object +is dead may not coincide with the programmer's expectations. +The only guarantees are that Lua will not collect an object +that may still be accessed in the normal execution of the program, +and it will eventually collect an object +that is inaccessible from Lua. +(Here, +inaccessible from Lua means that neither a variable nor +another live object refer to the object.) +Because Lua has no knowledge about C code, +it never collects objects accessible through the registry (see §4.3), +which includes the global environment (see §2.2). + + +
+The garbage collector (GC) in Lua can work in two modes: +incremental and generational. + + +
+The default GC mode with the default parameters +are adequate for most uses. +However, programs that waste a large proportion of their time +allocating and freeing memory can benefit from other settings. +Keep in mind that the GC behavior is non-portable +both across platforms and across different Lua releases; +therefore, optimal settings are also non-portable. + + +
+You can change the GC mode and parameters by calling
+lua_gc in C
+or collectgarbage in Lua.
+You can also use these functions to control
+the collector directly (e.g., to stop and restart it).
+
+
+
+
+
+
+In incremental mode, +each GC cycle performs a mark-and-sweep collection in small steps +interleaved with the program's execution. +In this mode, +the collector uses three numbers to control its garbage-collection cycles: +the garbage-collector pause, +the garbage-collector step multiplier, +and the garbage-collector step size. + + +
+The garbage-collector pause +controls how long the collector waits before starting a new cycle. +The collector starts a new cycle when the use of memory +hits n% of the use after the previous collection. +Larger values make the collector less aggressive. +Values equal to or less than 100 mean the collector will not wait to +start a new cycle. +A value of 200 means that the collector waits for the total memory in use +to double before starting a new cycle. +The default value is 200; the maximum value is 1000. + + +
+The garbage-collector step multiplier +controls the speed of the collector relative to +memory allocation, +that is, +how many elements it marks or sweeps for each +kilobyte of memory allocated. +Larger values make the collector more aggressive but also increase +the size of each incremental step. +You should not use values less than 100, +because they make the collector too slow and +can result in the collector never finishing a cycle. +The default value is 100; the maximum value is 1000. + + +
+The garbage-collector step size controls the +size of each incremental step, +specifically how many bytes the interpreter allocates +before performing a step. +This parameter is logarithmic: +A value of n means the interpreter will allocate 2n +bytes between steps and perform equivalent work during the step. +A large value (e.g., 60) makes the collector a stop-the-world +(non-incremental) collector. +The default value is 13, +which means steps of approximately 8 Kbytes. + + + + + +
+In generational mode, +the collector does frequent minor collections, +which traverses only objects recently created. +If after a minor collection the use of memory is still above a limit, +the collector does a stop-the-world major collection, +which traverses all objects. +The generational mode uses two parameters: +the minor multiplier and the the major multiplier. + + +
+The minor multiplier controls the frequency of minor collections. +For a minor multiplier x, +a new minor collection will be done when memory +grows x% larger than the memory in use after the previous major +collection. +For instance, for a multiplier of 20, +the collector will do a minor collection when the use of memory +gets 20% larger than the use after the previous major collection. +The default value is 20; the maximum value is 200. + + +
+The major multiplier controls the frequency of major collections. +For a major multiplier x, +a new major collection will be done when memory +grows x% larger than the memory in use after the previous major +collection. +For instance, for a multiplier of 100, +the collector will do a major collection when the use of memory +gets larger than twice the use after the previous collection. +The default value is 100; the maximum value is 1000. + + + + + +
+You can set garbage-collector metamethods for tables +and, using the C API, +for full userdata (see §2.4). +These metamethods, called finalizers, +are called when the garbage collector detects that the +corresponding table or userdata is dead. +Finalizers allow you to coordinate Lua's garbage collection +with external resource management such as closing files, +network or database connections, +or freeing your own memory. + + +
+For an object (table or userdata) to be finalized when collected,
+you must mark it for finalization.
+
+You mark an object for finalization when you set its metatable
+and the metatable has a __gc metamethod.
+Note that if you set a metatable without a __gc field
+and later create that field in the metatable,
+the object will not be marked for finalization.
+
+
+
+When a marked object becomes dead,
+it is not collected immediately by the garbage collector.
+Instead, Lua puts it in a list.
+After the collection,
+Lua goes through that list.
+For each object in the list,
+it checks the object's __gc metamethod:
+If it is present,
+Lua calls it with the object as its single argument.
+
+
+
+At the end of each garbage-collection cycle, +the finalizers are called in +the reverse order that the objects were marked for finalization, +among those collected in that cycle; +that is, the first finalizer to be called is the one associated +with the object marked last in the program. +The execution of each finalizer may occur at any point during +the execution of the regular code. + + +
+Because the object being collected must still be used by the finalizer, +that object (and other objects accessible only through it) +must be resurrected by Lua. +Usually, this resurrection is transient, +and the object memory is freed in the next garbage-collection cycle. +However, if the finalizer stores the object in some global place +(e.g., a global variable), +then the resurrection is permanent. +Moreover, if the finalizer marks a finalizing object for finalization again, +its finalizer will be called again in the next cycle where the +object is dead. +In any case, +the object memory is freed only in a GC cycle where +the object is dead and not marked for finalization. + + +
+When you close a state (see lua_close),
+Lua calls the finalizers of all objects marked for finalization,
+following the reverse order that they were marked.
+If any finalizer marks objects for collection during that phase,
+these marks have no effect.
+
+
+
+Finalizers cannot yield nor run the garbage collector. +Because they can run in unpredictable times, +it is good practice to restrict each finalizer +to the minimum necessary to properly release +its associated resource. + + +
+Any error while running a finalizer generates a warning; +the error is not propagated. + + + + + +
+A weak table is a table whose elements are +weak references. +A weak reference is ignored by the garbage collector. +In other words, +if the only references to an object are weak references, +then the garbage collector will collect that object. + + +
+A weak table can have weak keys, weak values, or both.
+A table with weak values allows the collection of its values,
+but prevents the collection of its keys.
+A table with both weak keys and weak values allows the collection of
+both keys and values.
+In any case, if either the key or the value is collected,
+the whole pair is removed from the table.
+The weakness of a table is controlled by the
+__mode field of its metatable.
+This metavalue, if present, must be one of the following strings:
+"k", for a table with weak keys;
+"v", for a table with weak values;
+or "kv", for a table with both weak keys and values.
+
+
+
+A table with weak keys and strong values +is also called an ephemeron table. +In an ephemeron table, +a value is considered reachable only if its key is reachable. +In particular, +if the only reference to a key comes through its value, +the pair is removed. + + +
+Any change in the weakness of a table may take effect only +at the next collect cycle. +In particular, if you change the weakness to a stronger mode, +Lua may still collect some items from that table +before the change takes effect. + + +
+Only objects that have an explicit construction +are removed from weak tables. +Values, such as numbers and light C functions, +are not subject to garbage collection, +and therefore are not removed from weak tables +(unless their associated values are collected). +Although strings are subject to garbage collection, +they do not have an explicit construction and +their equality is by value; +they behave more like values than like objects. +Therefore, they are not removed from weak tables. + + +
+Resurrected objects +(that is, objects being finalized +and objects accessible only through objects being finalized) +have a special behavior in weak tables. +They are removed from weak values before running their finalizers, +but are removed from weak keys only in the next collection +after running their finalizers, when such objects are actually freed. +This behavior allows the finalizer to access properties +associated with the object through weak tables. + + +
+If a weak table is among the resurrected objects in a collection cycle, +it may not be properly cleared until the next cycle. + + + + + + + +
+Lua supports coroutines, +also called collaborative multithreading. +A coroutine in Lua represents an independent thread of execution. +Unlike threads in multithread systems, however, +a coroutine only suspends its execution by explicitly calling +a yield function. + + +
+You create a coroutine by calling coroutine.create.
+Its sole argument is a function
+that is the main function of the coroutine.
+The create function only creates a new coroutine and
+returns a handle to it (an object of type thread);
+it does not start the coroutine.
+
+
+
+You execute a coroutine by calling coroutine.resume.
+When you first call coroutine.resume,
+passing as its first argument
+a thread returned by coroutine.create,
+the coroutine starts its execution by
+calling its main function.
+Extra arguments passed to coroutine.resume are passed
+as arguments to that function.
+After the coroutine starts running,
+it runs until it terminates or yields.
+
+
+
+A coroutine can terminate its execution in two ways:
+normally, when its main function returns
+(explicitly or implicitly, after the last instruction);
+and abnormally, if there is an unprotected error.
+In case of normal termination,
+coroutine.resume returns true,
+plus any values returned by the coroutine main function.
+In case of errors, coroutine.resume returns false
+plus the error object.
+In this case, the coroutine does not unwind its stack,
+so that it is possible to inspect it after the error
+with the debug API.
+
+
+
+A coroutine yields by calling coroutine.yield.
+When a coroutine yields,
+the corresponding coroutine.resume returns immediately,
+even if the yield happens inside nested function calls
+(that is, not in the main function,
+but in a function directly or indirectly called by the main function).
+In the case of a yield, coroutine.resume also returns true,
+plus any values passed to coroutine.yield.
+The next time you resume the same coroutine,
+it continues its execution from the point where it yielded,
+with the call to coroutine.yield returning any extra
+arguments passed to coroutine.resume.
+
+
+
+Like coroutine.create,
+the coroutine.wrap function also creates a coroutine,
+but instead of returning the coroutine itself,
+it returns a function that, when called, resumes the coroutine.
+Any arguments passed to this function
+go as extra arguments to coroutine.resume.
+coroutine.wrap returns all the values returned by coroutine.resume,
+except the first one (the boolean error code).
+Unlike coroutine.resume,
+the function created by coroutine.wrap
+propagates any error to the caller.
+In this case,
+the function also closes the coroutine (see coroutine.close).
+
+
+
+As an example of how coroutines work, +consider the following code: + +
+ function foo (a)
+ print("foo", a)
+ return coroutine.yield(2*a)
+ end
+
+ co = coroutine.create(function (a,b)
+ print("co-body", a, b)
+ local r = foo(a+1)
+ print("co-body", r)
+ local r, s = coroutine.yield(a+b, a-b)
+ print("co-body", r, s)
+ return b, "end"
+ end)
+
+ print("main", coroutine.resume(co, 1, 10))
+ print("main", coroutine.resume(co, "r"))
+ print("main", coroutine.resume(co, "x", "y"))
+ print("main", coroutine.resume(co, "x", "y"))
++When you run it, it produces the following output: + +
+ co-body 1 10 + foo 2 + main true 4 + co-body r + main true 11 -9 + co-body x y + main true 10 end + main false cannot resume dead coroutine ++ +
+You can also create and manipulate coroutines through the C API:
+see functions lua_newthread, lua_resume,
+and lua_yield.
+
+
+
+
+
+
+This section describes the lexis, the syntax, and the semantics of Lua. +In other words, +this section describes +which tokens are valid, +how they can be combined, +and what their combinations mean. + + +
+Language constructs will be explained using the usual extended BNF notation, +in which +{a} means 0 or more a's, and +[a] means an optional a. +Non-terminals are shown like non-terminal, +keywords are shown like kword, +and other terminal symbols are shown like ‘=’. +The complete syntax of Lua can be found in §9 +at the end of this manual. + + + + + +
+Lua is a free-form language. +It ignores spaces and comments between lexical elements (tokens), +except as delimiters between two tokens. +In source code, +Lua recognizes as spaces the standard ASCII whitespace +characters space, form feed, newline, +carriage return, horizontal tab, and vertical tab. + + +
+Names +(also called identifiers) +in Lua can be any string of Latin letters, +Arabic-Indic digits, and underscores, +not beginning with a digit and +not being a reserved word. +Identifiers are used to name variables, table fields, and labels. + + +
+The following keywords are reserved +and cannot be used as names: + + +
+ and break do else elseif end + false for function goto if in + local nil not or repeat return + then true until while ++ +
+Lua is a case-sensitive language:
+and is a reserved word, but And and AND
+are two different, valid names.
+As a convention,
+programs should avoid creating
+names that start with an underscore followed by
+one or more uppercase letters (such as _VERSION).
+
+
+
+The following strings denote other tokens: + +
+ + - * / % ^ #
+ & ~ | << >> //
+ == ~= <= >= < > =
+ ( ) { } [ ] ::
+ ; : , . .. ...
+
+
+
+A short literal string
+can be delimited by matching single or double quotes,
+and can contain the following C-like escape sequences:
+'\a' (bell),
+'\b' (backspace),
+'\f' (form feed),
+'\n' (newline),
+'\r' (carriage return),
+'\t' (horizontal tab),
+'\v' (vertical tab),
+'\\' (backslash),
+'\"' (quotation mark [double quote]),
+and '\'' (apostrophe [single quote]).
+A backslash followed by a line break
+results in a newline in the string.
+The escape sequence '\z' skips the following span
+of whitespace characters,
+including line breaks;
+it is particularly useful to break and indent a long literal string
+into multiple lines without adding the newlines and spaces
+into the string contents.
+A short literal string cannot contain unescaped line breaks
+nor escapes not forming a valid escape sequence.
+
+
+
+We can specify any byte in a short literal string,
+including embedded zeros,
+by its numeric value.
+This can be done
+with the escape sequence \xXX,
+where XX is a sequence of exactly two hexadecimal digits,
+or with the escape sequence \ddd,
+where ddd is a sequence of up to three decimal digits.
+(Note that if a decimal escape sequence is to be followed by a digit,
+it must be expressed using exactly three digits.)
+
+
+
+The UTF-8 encoding of a Unicode character
+can be inserted in a literal string with
+the escape sequence \u{XXX}
+(with mandatory enclosing braces),
+where XXX is a sequence of one or more hexadecimal digits
+representing the character code point.
+This code point can be any value less than 231.
+(Lua uses the original UTF-8 specification here,
+which is not restricted to valid Unicode code points.)
+
+
+
+Literal strings can also be defined using a long format
+enclosed by long brackets.
+We define an opening long bracket of level n as an opening
+square bracket followed by n equal signs followed by another
+opening square bracket.
+So, an opening long bracket of level 0 is written as [[,
+an opening long bracket of level 1 is written as [=[,
+and so on.
+A closing long bracket is defined similarly;
+for instance,
+a closing long bracket of level 4 is written as ]====].
+A long literal starts with an opening long bracket of any level and
+ends at the first closing long bracket of the same level.
+It can contain any text except a closing bracket of the same level.
+Literals in this bracketed form can run for several lines,
+do not interpret any escape sequences,
+and ignore long brackets of any other level.
+Any kind of end-of-line sequence
+(carriage return, newline, carriage return followed by newline,
+or newline followed by carriage return)
+is converted to a simple newline.
+When the opening long bracket is immediately followed by a newline,
+the newline is not included in the string.
+
+
+
+As an example, in a system using ASCII
+(in which 'a' is coded as 97,
+newline is coded as 10, and '1' is coded as 49),
+the five literal strings below denote the same string:
+
+
+ a = 'alo\n123"' + a = "alo\n123\"" + a = '\97lo\10\04923"' + a = [[alo + 123"]] + a = [==[ + alo + 123"]==] ++ +
+Any byte in a literal string not +explicitly affected by the previous rules represents itself. +However, Lua opens files for parsing in text mode, +and the system's file functions may have problems with +some control characters. +So, it is safer to represent +binary data as a quoted literal with +explicit escape sequences for the non-text characters. + + +
+A numeric constant (or numeral)
+can be written with an optional fractional part
+and an optional decimal exponent,
+marked by a letter 'e' or 'E'.
+Lua also accepts hexadecimal constants,
+which start with 0x or 0X.
+Hexadecimal constants also accept an optional fractional part
+plus an optional binary exponent,
+marked by a letter 'p' or 'P' and written in decimal.
+(For instance, 0x1.fp10 denotes 1984,
+which is 0x1f / 16 multiplied by 210.)
+
+
+
+A numeric constant with a radix point or an exponent +denotes a float; +otherwise, +if its value fits in an integer or it is a hexadecimal constant, +it denotes an integer; +otherwise (that is, a decimal integer numeral that overflows), +it denotes a float. +Hexadecimal numerals with neither a radix point nor an exponent +always denote an integer value; +if the value overflows, it wraps around +to fit into a valid integer. + + +
+Examples of valid integer constants are + +
+ 3 345 0xff 0xBEBADA +
+Examples of valid float constants are + +
+ 3.0 3.1416 314.16e-2 0.31416E1 34e1 + 0x0.1E 0xA23p-4 0X1.921FB54442D18P+1 ++ +
+A comment starts with a double hyphen (--)
+anywhere outside a string.
+If the text immediately after -- is not an opening long bracket,
+the comment is a short comment,
+which runs until the end of the line.
+Otherwise, it is a long comment,
+which runs until the corresponding closing long bracket.
+
+
+
+
+
+
+Variables are places that store values. +There are three kinds of variables in Lua: +global variables, local variables, and table fields. + + +
+A single name can denote a global variable or a local variable +(or a function's formal parameter, +which is a particular kind of local variable): + +
+ var ::= Name +
+Name denotes identifiers (see §3.1). + + +
+Any variable name is assumed to be global unless explicitly declared +as a local (see §3.3.7). +Local variables are lexically scoped: +local variables can be freely accessed by functions +defined inside their scope (see §3.5). + + +
+Before the first assignment to a variable, its value is nil. + + +
+Square brackets are used to index a table: + +
+ var ::= prefixexp ‘[’ exp ‘]’ +
+The meaning of accesses to table fields can be changed via metatables +(see §2.4). + + +
+The syntax var.Name is just syntactic sugar for
+var["Name"]:
+
+
+ var ::= prefixexp ‘.’ Name ++ +
+An access to a global variable x
+is equivalent to _ENV.x.
+Due to the way that chunks are compiled,
+the variable _ENV itself is never global (see §2.2).
+
+
+
+
+
+
+Lua supports an almost conventional set of statements, +similar to those in other conventional languages. +This set includes +blocks, assignments, control structures, function calls, +and variable declarations. + + + + + +
+A block is a list of statements, +which are executed sequentially: + +
+ block ::= {stat}
++Lua has empty statements +that allow you to separate statements with semicolons, +start a block with a semicolon +or write two semicolons in sequence: + +
+ stat ::= ‘;’ ++ +
+Both function calls and assignments +can start with an open parenthesis. +This possibility leads to an ambiguity in Lua's grammar. +Consider the following fragment: + +
+ a = b + c
+ (print or io.write)('done')
++The grammar could see this fragment in two ways: + +
+ a = b + c(print or io.write)('done')
+
+ a = b + c; (print or io.write)('done')
++The current parser always sees such constructions +in the first way, +interpreting the open parenthesis +as the start of the arguments to a call. +To avoid this ambiguity, +it is a good practice to always precede with a semicolon +statements that start with a parenthesis: + +
+ ;(print or io.write)('done')
+
+
++A block can be explicitly delimited to produce a single statement: + +
+ stat ::= do block end +
+Explicit blocks are useful +to control the scope of variable declarations. +Explicit blocks are also sometimes used to +add a return statement in the middle +of another block (see §3.3.4). + + + + + +
+The unit of compilation of Lua is called a chunk. +Syntactically, +a chunk is simply a block: + +
+ chunk ::= block ++ +
+Lua handles a chunk as the body of an anonymous function
+with a variable number of arguments
+(see §3.4.11).
+As such, chunks can define local variables,
+receive arguments, and return values.
+Moreover, such anonymous function is compiled as in the
+scope of an external local variable called _ENV (see §2.2).
+The resulting function always has _ENV as its only external variable,
+even if it does not use that variable.
+
+
+
+A chunk can be stored in a file or in a string inside the host program. +To execute a chunk, +Lua first loads it, +precompiling the chunk's code into instructions for a virtual machine, +and then Lua executes the compiled code +with an interpreter for the virtual machine. + + +
+Chunks can also be precompiled into binary form;
+see the program luac and the function string.dump for details.
+Programs in source and compiled forms are interchangeable;
+Lua automatically detects the file type and acts accordingly (see load).
+
+
+
+
+
+
+Lua allows multiple assignments. +Therefore, the syntax for assignment +defines a list of variables on the left side +and a list of expressions on the right side. +The elements in both lists are separated by commas: + +
+ stat ::= varlist ‘=’ explist
+ varlist ::= var {‘,’ var}
+ explist ::= exp {‘,’ exp}
++Expressions are discussed in §3.4. + + +
+Before the assignment, +the list of values is adjusted to the length of +the list of variables (see §3.4.12). + + +
+If a variable is both assigned and read +inside a multiple assignment, +Lua ensures that all reads get the value of the variable +before the assignment. +Thus the code + +
+ i = 3 + i, a[i] = i+1, 20 +
+sets a[3] to 20, without affecting a[4]
+because the i in a[i] is evaluated (to 3)
+before it is assigned 4.
+Similarly, the line
+
+
+ x, y = y, x +
+exchanges the values of x and y,
+and
+
+
+ x, y, z = y, z, x +
+cyclically permutes the values of x, y, and z.
+
+
+
+Note that this guarantee covers only accesses +syntactically inside the assignment statement. +If a function or a metamethod called during the assignment +changes the value of a variable, +Lua gives no guarantees about the order of that access. + + +
+An assignment to a global name x = val
+is equivalent to the assignment
+_ENV.x = val (see §2.2).
+
+
+
+The meaning of assignments to table fields and +global variables (which are actually table fields, too) +can be changed via metatables (see §2.4). + + + + + +
+The control structures +if, while, and repeat have the usual meaning and +familiar syntax: + + + + +
+ stat ::= while exp do block end
+ stat ::= repeat block until exp
+ stat ::= if exp then block {elseif exp then block} [else block] end
++Lua also has a for statement, in two flavors (see §3.3.5). + + +
+The condition expression of a +control structure can return any value. +Both false and nil test false. +All values different from nil and false test true. +In particular, the number 0 and the empty string also test true. + + +
+In the repeat–until loop, +the inner block does not end at the until keyword, +but only after the condition. +So, the condition can refer to local variables +declared inside the loop block. + + +
+The goto statement transfers the program control to a label. +For syntactical reasons, +labels in Lua are considered statements too: + + + +
+ stat ::= goto Name + stat ::= label + label ::= ‘::’ Name ‘::’ ++ +
+A label is visible in the entire block where it is defined, +except inside nested functions. +A goto can jump to any visible label as long as it does not +enter into the scope of a local variable. +A label should not be declared +where a label with the same name is visible, +even if this other label has been declared in an enclosing block. + + +
+The break statement terminates the execution of a +while, repeat, or for loop, +skipping to the next statement after the loop: + + +
+ stat ::= break +
+A break ends the innermost enclosing loop. + + +
+The return statement is used to return values +from a function or a chunk +(which is handled as an anonymous function). + +Functions can return more than one value, +so the syntax for the return statement is + +
+ stat ::= return [explist] [‘;’] ++ +
+The return statement can only be written
+as the last statement of a block.
+If it is necessary to return in the middle of a block,
+then an explicit inner block can be used,
+as in the idiom do return end,
+because now return is the last statement in its (inner) block.
+
+
+
+
+
+
+ +The for statement has two forms: +one numerical and one generic. + + + +
+The numerical for loop repeats a block of code while a +control variable goes through an arithmetic progression. +It has the following syntax: + +
+ stat ::= for Name ‘=’ exp ‘,’ exp [‘,’ exp] do block end +
+The given identifier (Name) defines the control variable, +which is a new variable local to the loop body (block). + + +
+The loop starts by evaluating once the three control expressions. +Their values are called respectively +the initial value, the limit, and the step. +If the step is absent, it defaults to 1. + + +
+If both the initial value and the step are integers, +the loop is done with integers; +note that the limit may not be an integer. +Otherwise, the three values are converted to +floats and the loop is done with floats. +Beware of floating-point accuracy in this case. + + +
+After that initialization, +the loop body is repeated with the value of the control variable +going through an arithmetic progression, +starting at the initial value, +with a common difference given by the step. +A negative step makes a decreasing sequence; +a step equal to zero raises an error. +The loop continues while the value is less than +or equal to the limit +(greater than or equal to for a negative step). +If the initial value is already greater than the limit +(or less than, if the step is negative), +the body is not executed. + + +
+For integer loops, +the control variable never wraps around; +instead, the loop ends in case of an overflow. + + +
+You should not change the value of the control variable +during the loop. +If you need its value after the loop, +assign it to another variable before exiting the loop. + + + + + +
+The generic for statement works over functions, +called iterators. +On each iteration, the iterator function is called to produce a new value, +stopping when this new value is nil. +The generic for loop has the following syntax: + +
+ stat ::= for namelist in explist do block end
+ namelist ::= Name {‘,’ Name}
++A for statement like + +
+ for var_1, ···, var_n in explist do body end +
+works as follows. + + +
+The names var_i declare loop variables local to the loop body. +The first of these variables is the control variable. + + +
+The loop starts by evaluating explist +to produce four values: +an iterator function, +a state, +an initial value for the control variable, +and a closing value. + + +
+Then, at each iteration, +Lua calls the iterator function with two arguments: +the state and the control variable. +The results from this call are then assigned to the loop variables, +following the rules of multiple assignments (see §3.3.3). +If the control variable becomes nil, +the loop terminates. +Otherwise, the body is executed and the loop goes +to the next iteration. + + +
+The closing value behaves like a +to-be-closed variable (see §3.3.8), +which can be used to release resources when the loop ends. +Otherwise, it does not interfere with the loop. + + +
+You should not change the value of the control variable +during the loop. + + + + + + + +
+To allow possible side-effects, +function calls can be executed as statements: + +
+ stat ::= functioncall +
+In this case, all returned values are thrown away. +Function calls are explained in §3.4.10. + + + + + +
+Local variables can be declared anywhere inside a block. +The declaration can include an initialization: + +
+ stat ::= local attnamelist [‘=’ explist]
+ attnamelist ::= Name attrib {‘,’ Name attrib}
++If present, an initial assignment has the same semantics +of a multiple assignment (see §3.3.3). +Otherwise, all variables are initialized with nil. + + +
+Each variable name may be postfixed by an attribute +(a name between angle brackets): + +
+ attrib ::= [‘<’ Name ‘>’] +
+There are two possible attributes:
+const, which declares a constant variable,
+that is, a variable that cannot be assigned to
+after its initialization;
+and close, which declares a to-be-closed variable (see §3.3.8).
+A list of variables can contain at most one to-be-closed variable.
+
+
+
+A chunk is also a block (see §3.3.2), +and so local variables can be declared in a chunk outside any explicit block. + + +
+The visibility rules for local variables are explained in §3.5. + + + + + +
+A to-be-closed variable behaves like a constant local variable, +except that its value is closed whenever the variable +goes out of scope, including normal block termination, +exiting its block by break/goto/return, +or exiting by an error. + + +
+Here, to close a value means
+to call its __close metamethod.
+When calling the metamethod,
+the value itself is passed as the first argument
+and the error object that caused the exit (if any)
+is passed as a second argument;
+if there was no error, the second argument is nil.
+
+
+
+The value assigned to a to-be-closed variable
+must have a __close metamethod
+or be a false value.
+(nil and false are ignored as to-be-closed values.)
+
+
+
+If several to-be-closed variables go out of scope at the same event, +they are closed in the reverse order that they were declared. + + +
+If there is any error while running a closing method, +that error is handled like an error in the regular code +where the variable was defined. +After an error, +the other pending closing methods will still be called. + + +
+If a coroutine yields and is never resumed again,
+some variables may never go out of scope,
+and therefore they will never be closed.
+(These variables are the ones created inside the coroutine
+and in scope at the point where the coroutine yielded.)
+Similarly, if a coroutine ends with an error,
+it does not unwind its stack,
+so it does not close any variable.
+In both cases,
+you can either use finalizers
+or call coroutine.close to close the variables.
+However, if the coroutine was created
+through coroutine.wrap,
+then its corresponding function will close the coroutine
+in case of errors.
+
+
+
+
+
+
+
+
+The basic expressions in Lua are the following: + +
+ exp ::= prefixexp + exp ::= nil | false | true + exp ::= Numeral + exp ::= LiteralString + exp ::= functiondef + exp ::= tableconstructor + exp ::= ‘...’ + exp ::= exp binop exp + exp ::= unop exp + prefixexp ::= var | functioncall | ‘(’ exp ‘)’ ++ +
+Numerals and literal strings are explained in §3.1;
+variables are explained in §3.2;
+function definitions are explained in §3.4.11;
+function calls are explained in §3.4.10;
+table constructors are explained in §3.4.9.
+Vararg expressions,
+denoted by three dots ('...'), can only be used when
+directly inside a variadic function;
+they are explained in §3.4.11.
+
+
+
+Binary operators comprise arithmetic operators (see §3.4.1), +bitwise operators (see §3.4.2), +relational operators (see §3.4.4), logical operators (see §3.4.5), +and the concatenation operator (see §3.4.6). +Unary operators comprise the unary minus (see §3.4.1), +the unary bitwise NOT (see §3.4.2), +the unary logical not (see §3.4.5), +and the unary length operator (see §3.4.7). + + + + + +
+Lua supports the following arithmetic operators: + +
+: addition-: subtraction*: multiplication/: float division//: floor division%: modulo^: exponentiation-: unary minus+With the exception of exponentiation and float division, +the arithmetic operators work as follows: +If both operands are integers, +the operation is performed over integers and the result is an integer. +Otherwise, if both operands are numbers, +then they are converted to floats, +the operation is performed following the machine's rules +for floating-point arithmetic +(usually the IEEE 754 standard), +and the result is a float. +(The string library coerces strings to numbers in +arithmetic operations; see §3.4.3 for details.) + + +
+Exponentiation and float division (/)
+always convert their operands to floats
+and the result is always a float.
+Exponentiation uses the ISO C function pow,
+so that it works for non-integer exponents too.
+
+
+
+Floor division (//) is a division
+that rounds the quotient towards minus infinity,
+resulting in the floor of the division of its operands.
+
+
+
+Modulo is defined as the remainder of a division +that rounds the quotient towards minus infinity (floor division). + + +
+In case of overflows in integer arithmetic, +all operations wrap around. + + + +
+Lua supports the following bitwise operators: + +
&: bitwise AND|: bitwise OR~: bitwise exclusive OR>>: right shift<<: left shift~: unary bitwise NOT+All bitwise operations convert its operands to integers +(see §3.4.3), +operate on all bits of those integers, +and result in an integer. + + +
+Both right and left shifts fill the vacant bits with zeros. +Negative displacements shift to the other direction; +displacements with absolute values equal to or higher than +the number of bits in an integer +result in zero (as all bits are shifted out). + + + + + +
+Lua provides some automatic conversions between some +types and representations at run time. +Bitwise operators always convert float operands to integers. +Exponentiation and float division +always convert integer operands to floats. +All other arithmetic operations applied to mixed numbers +(integers and floats) convert the integer operand to a float. +The C API also converts both integers to floats and +floats to integers, as needed. +Moreover, string concatenation accepts numbers as arguments, +besides strings. + + +
+In a conversion from integer to float, +if the integer value has an exact representation as a float, +that is the result. +Otherwise, +the conversion gets the nearest higher or +the nearest lower representable value. +This kind of conversion never fails. + + +
+The conversion from float to integer +checks whether the float has an exact representation as an integer +(that is, the float has an integral value and +it is in the range of integer representation). +If it does, that representation is the result. +Otherwise, the conversion fails. + + +
+Several places in Lua coerce strings to numbers when necessary. +In particular, +the string library sets metamethods that try to coerce +strings to numbers in all arithmetic operations. +If the conversion fails, +the library calls the metamethod of the other operand +(if present) or it raises an error. +Note that bitwise operators do not do this coercion. + + +
+It is always a good practice not to rely on the
+implicit coercions from strings to numbers,
+as they are not always applied;
+in particular, "1"==1 is false and "1"<1 raises an error
+(see §3.4.4).
+These coercions exist mainly for compatibility and may be removed
+in future versions of the language.
+
+
+
+A string is converted to an integer or a float +following its syntax and the rules of the Lua lexer. +The string may have also leading and trailing whitespaces and a sign. +All conversions from strings to numbers +accept both a dot and the current locale mark +as the radix character. +(The Lua lexer, however, accepts only a dot.) +If the string is not a valid numeral, +the conversion fails. +If necessary, the result of this first step is then converted +to a specific number subtype following the previous rules +for conversions between floats and integers. + + +
+The conversion from numbers to strings uses a
+non-specified human-readable format.
+To convert numbers to strings in any specific way,
+use the function string.format.
+
+
+
+
+
+
+Lua supports the following relational operators: + +
==: equality~=: inequality<: less than>: greater than<=: less or equal>=: greater or equal+These operators always result in false or true. + + +
+Equality (==) first compares the type of its operands.
+If the types are different, then the result is false.
+Otherwise, the values of the operands are compared.
+Strings are equal if they have the same byte content.
+Numbers are equal if they denote the same mathematical value.
+
+
+
+Tables, userdata, and threads +are compared by reference: +two objects are considered equal only if they are the same object. +Every time you create a new object +(a table, a userdata, or a thread), +this new object is different from any previously existing object. +A function is always equal to itself. +Functions with any detectable difference +(different behavior, different definition) are always different. +Functions created at different times but with no detectable differences +may be classified as equal or not +(depending on internal caching details). + + +
+You can change the way that Lua compares tables and userdata
+by using the __eq metamethod (see §2.4).
+
+
+
+Equality comparisons do not convert strings to numbers
+or vice versa.
+Thus, "0"==0 evaluates to false,
+and t[0] and t["0"] denote different
+entries in a table.
+
+
+
+The operator ~= is exactly the negation of equality (==).
+
+
+
+The order operators work as follows.
+If both arguments are numbers,
+then they are compared according to their mathematical values,
+regardless of their subtypes.
+Otherwise, if both arguments are strings,
+then their values are compared according to the current locale.
+Otherwise, Lua tries to call the __lt or the __le
+metamethod (see §2.4).
+A comparison a > b is translated to b < a
+and a >= b is translated to b <= a.
+
+
+
+Following the IEEE 754 standard, +the special value NaN is considered neither less than, +nor equal to, nor greater than any value, including itself. + + + + + +
+The logical operators in Lua are +and, or, and not. +Like the control structures (see §3.3.4), +all logical operators consider both false and nil as false +and anything else as true. + + +
+The negation operator not always returns false or true. +The conjunction operator and returns its first argument +if this value is false or nil; +otherwise, and returns its second argument. +The disjunction operator or returns its first argument +if this value is different from nil and false; +otherwise, or returns its second argument. +Both and and or use short-circuit evaluation; +that is, +the second operand is evaluated only if necessary. +Here are some examples: + +
+ 10 or 20 --> 10 + 10 or error() --> 10 + nil or "a" --> "a" + nil and 10 --> nil + false and error() --> false + false and nil --> false + false or nil --> nil + 10 and 20 --> 20 ++ + + + +
+The string concatenation operator in Lua is
+denoted by two dots ('..').
+If both operands are strings or numbers,
+then the numbers are converted to strings
+in a non-specified format (see §3.4.3).
+Otherwise, the __concat metamethod is called (see §2.4).
+
+
+
+
+
+
+The length operator is denoted by the unary prefix operator #.
+
+
+
+The length of a string is its number of bytes. +(That is the usual meaning of string length when each +character is one byte.) + + +
+The length operator applied on a table
+returns a border in that table.
+A border in a table t is any non-negative integer
+that satisfies the following condition:
+
+
+ (border == 0 or t[border] ~= nil) and + (t[border + 1] == nil or border == math.maxinteger) +
+In words, +a border is any positive integer index present in the table +that is followed by an absent index, +plus two limit cases: +zero, when index 1 is absent; +and the maximum value for an integer, when that index is present. +Note that keys that are not positive integers +do not interfere with borders. + + +
+A table with exactly one border is called a sequence.
+For instance, the table {10, 20, 30, 40, 50} is a sequence,
+as it has only one border (5).
+The table {10, 20, 30, nil, 50} has two borders (3 and 5),
+and therefore it is not a sequence.
+(The nil at index 4 is called a hole.)
+The table {nil, 20, 30, nil, nil, 60, nil}
+has three borders (0, 3, and 6),
+so it is not a sequence, too.
+The table {} is a sequence with border 0.
+
+
+
+When t is a sequence,
+#t returns its only border,
+which corresponds to the intuitive notion of the length of the sequence.
+When t is not a sequence,
+#t can return any of its borders.
+(The exact one depends on details of
+the internal representation of the table,
+which in turn can depend on how the table was populated and
+the memory addresses of its non-numeric keys.)
+
+
+
+The computation of the length of a table +has a guaranteed worst time of O(log n), +where n is the largest integer key in the table. + + +
+A program can modify the behavior of the length operator for
+any value but strings through the __len metamethod (see §2.4).
+
+
+
+
+
+
+Operator precedence in Lua follows the table below, +from lower to higher priority: + +
+ or + and + < > <= >= ~= == + | + ~ + & + << >> + .. + + - + * / // % + unary operators (not # - ~) + ^ +
+As usual,
+you can use parentheses to change the precedences of an expression.
+The concatenation ('..') and exponentiation ('^')
+operators are right associative.
+All other binary operators are left associative.
+
+
+
+
+
+
+Table constructors are expressions that create tables. +Every time a constructor is evaluated, a new table is created. +A constructor can be used to create an empty table +or to create a table and initialize some of its fields. +The general syntax for constructors is + +
+ tableconstructor ::= ‘{’ [fieldlist] ‘}’
+ fieldlist ::= field {fieldsep field} [fieldsep]
+ field ::= ‘[’ exp ‘]’ ‘=’ exp | Name ‘=’ exp | exp
+ fieldsep ::= ‘,’ | ‘;’
+
+
+
+Each field of the form [exp1] = exp2 adds to the new table an entry
+with key exp1 and value exp2.
+A field of the form name = exp is equivalent to
+["name"] = exp.
+Fields of the form exp are equivalent to
+[i] = exp, where i are consecutive integers
+starting with 1;
+fields in the other formats do not affect this counting.
+For example,
+
+
+ a = { [f(1)] = g; "x", "y"; x = 1, f(x), [30] = 23; 45 }
++is equivalent to + +
+ do
+ local t = {}
+ t[f(1)] = g
+ t[1] = "x" -- 1st exp
+ t[2] = "y" -- 2nd exp
+ t.x = 1 -- t["x"] = 1
+ t[3] = f(x) -- 3rd exp
+ t[30] = 23
+ t[4] = 45 -- 4th exp
+ a = t
+ end
+
+
++The order of the assignments in a constructor is undefined. +(This order would be relevant only when there are repeated keys.) + + +
+If the last field in the list has the form exp
+and the expression is a multires expression,
+then all values returned by this expression enter the list consecutively
+(see §3.4.12).
+
+
+
+The field list can have an optional trailing separator, +as a convenience for machine-generated code. + + + + + +
+A function call in Lua has the following syntax: + +
+ functioncall ::= prefixexp args +
+In a function call,
+first prefixexp and args are evaluated.
+If the value of prefixexp has type function,
+then this function is called
+with the given arguments.
+Otherwise, if present,
+the prefixexp __call metamethod is called:
+its first argument is the value of prefixexp,
+followed by the original call arguments
+(see §2.4).
+
+
+
+The form + +
+ functioncall ::= prefixexp ‘:’ Name args +
+can be used to emulate methods.
+A call v:name(args)
+is syntactic sugar for v.name(v,args),
+except that v is evaluated only once.
+
+
+
+Arguments have the following syntax: + +
+ args ::= ‘(’ [explist] ‘)’ + args ::= tableconstructor + args ::= LiteralString +
+All argument expressions are evaluated before the call.
+A call of the form f{fields} is
+syntactic sugar for f({fields});
+that is, the argument list is a single new table.
+A call of the form f'string'
+(or f"string" or f[[string]])
+is syntactic sugar for f('string');
+that is, the argument list is a single literal string.
+
+
+
+A call of the form return functioncall not in the
+scope of a to-be-closed variable is called a tail call.
+Lua implements proper tail calls
+(or proper tail recursion):
+In a tail call,
+the called function reuses the stack entry of the calling function.
+Therefore, there is no limit on the number of nested tail calls that
+a program can execute.
+However, a tail call erases any debug information about the
+calling function.
+Note that a tail call only happens with a particular syntax,
+where the return has one single function call as argument,
+and it is outside the scope of any to-be-closed variable.
+This syntax makes the calling function return exactly
+the returns of the called function,
+without any intervening action.
+So, none of the following examples are tail calls:
+
+
+ return (f(x)) -- results adjusted to 1 + return 2 * f(x) -- result multiplied by 2 + return x, f(x) -- additional results + f(x); return -- results discarded + return x or f(x) -- results adjusted to 1 ++ + + + +
+The syntax for function definition is + +
+ functiondef ::= function funcbody + funcbody ::= ‘(’ [parlist] ‘)’ block end ++ +
+The following syntactic sugar simplifies function definitions: + +
+ stat ::= function funcname funcbody
+ stat ::= local function Name funcbody
+ funcname ::= Name {‘.’ Name} [‘:’ Name]
++The statement + +
+ function f () body end +
+translates to + +
+ f = function () body end +
+The statement + +
+ function t.a.b.c.f () body end +
+translates to + +
+ t.a.b.c.f = function () body end +
+The statement + +
+ local function f () body end +
+translates to + +
+ local f; f = function () body end +
+not to + +
+ local f = function () body end +
+(This only makes a difference when the body of the function
+contains references to f.)
+
+
+
+A function definition is an executable expression, +whose value has type function. +When Lua precompiles a chunk, +all its function bodies are precompiled too, +but they are not created yet. +Then, whenever Lua executes the function definition, +the function is instantiated (or closed). +This function instance, or closure, +is the final value of the expression. + + +
+Parameters act as local variables that are +initialized with the argument values: + +
+ parlist ::= namelist [‘,’ ‘...’] | ‘...’ +
+When a Lua function is called,
+it adjusts its list of arguments to
+the length of its list of parameters (see §3.4.12),
+unless the function is a variadic function,
+which is indicated by three dots ('...')
+at the end of its parameter list.
+A variadic function does not adjust its argument list;
+instead, it collects all extra arguments and supplies them
+to the function through a vararg expression,
+which is also written as three dots.
+The value of this expression is a list of all actual extra arguments,
+similar to a function with multiple results (see §3.4.12).
+
+
+
+As an example, consider the following definitions: + +
+ function f(a, b) end + function g(a, b, ...) end + function r() return 1,2,3 end +
+Then, we have the following mapping from arguments to parameters and +to the vararg expression: + +
+ CALL PARAMETERS + + f(3) a=3, b=nil + f(3, 4) a=3, b=4 + f(3, 4, 5) a=3, b=4 + f(r(), 10) a=1, b=10 + f(r()) a=1, b=2 + + g(3) a=3, b=nil, ... --> (nothing) + g(3, 4) a=3, b=4, ... --> (nothing) + g(3, 4, 5, 8) a=3, b=4, ... --> 5 8 + g(5, r()) a=5, b=1, ... --> 2 3 ++ +
+Results are returned using the return statement (see §3.3.4). +If control reaches the end of a function +without encountering a return statement, +then the function returns with no results. + + +
+ +There is a system-dependent limit on the number of values +that a function may return. +This limit is guaranteed to be greater than 1000. + + +
+The colon syntax
+is used to emulate methods,
+adding an implicit extra parameter self to the function.
+Thus, the statement
+
+
+ function t.a.b.c:f (params) body end +
+is syntactic sugar for + +
+ t.a.b.c.f = function (self, params) body end ++ + + + +
+Both function calls and vararg expressions can result in multiple values. +These expressions are called multires expressions. + + +
+When a multires expression is used as the last element +of a list of expressions, +all results from the expression are added to the +list of values produced by the list of expressions. +Note that a single expression +in a place that expects a list of expressions +is the last expression in that (singleton) list. + + +
+These are the places where Lua expects a list of expressions: + +
return e1, e2, e3 (see §3.3.4).{e1, e2, e3} (see §3.4.9).foo(e1, e2, e3) (see §3.4.10).a , b, c = e1, e2, e3 (see §3.3.3).local a , b, c = e1, e2, e3 (see §3.3.7).for k in e1, e2, e3 do ... end (see §3.3.5).+In the last four cases, +the list of values from the list of expressions +must be adjusted to a specific length: +the number of parameters in a call to a non-variadic function +(see §3.4.11), +the number of variables in a multiple assignment or +a local declaration, +and exactly four values for a generic for loop. +The adjustment follows these rules: +If there are more values than needed, +the extra values are thrown away; +if there are fewer values than needed, +the list is extended with nil's. +When the list of expressions ends with a multires expression, +all results from that expression enter the list of values +before the adjustment. + + +
+When a multires expression is used +in a list of expressions without being the last element, +or in a place where the syntax expects a single expression, +Lua adjusts the result list of that expression to one element. +As a particular case, +the syntax expects a single expression inside a parenthesized expression; +therefore, adding parentheses around a multires expression +forces it to produce exactly one result. + + +
+We seldom need to use a vararg expression in a place +where the syntax expects a single expression. +(Usually it is simpler to add a regular parameter before +the variadic part and use that parameter.) +When there is such a need, +we recommend assigning the vararg expression +to a single variable and using that variable +in its place. + + +
+Here are some examples of uses of mutlres expressions. +In all cases, when the construction needs +"the n-th result" and there is no such result, +it uses a nil. + +
+ print(x, f()) -- prints x and all results from f().
+ print(x, (f())) -- prints x and the first result from f().
+ print(f(), x) -- prints the first result from f() and x.
+ print(1 + f()) -- prints 1 added to the first result from f().
+ local x = ... -- x gets the first vararg argument.
+ x,y = ... -- x gets the first vararg argument,
+ -- y gets the second vararg argument.
+ x,y,z = w, f() -- x gets w, y gets the first result from f(),
+ -- z gets the second result from f().
+ x,y,z = f() -- x gets the first result from f(),
+ -- y gets the second result from f(),
+ -- z gets the third result from f().
+ x,y,z = f(), g() -- x gets the first result from f(),
+ -- y gets the first result from g(),
+ -- z gets the second result from g().
+ x,y,z = (f()) -- x gets the first result from f(), y and z get nil.
+ return f() -- returns all results from f().
+ return x, ... -- returns x and all received vararg arguments.
+ return x,y,f() -- returns x, y, and all results from f().
+ {f()} -- creates a list with all results from f().
+ {...} -- creates a list with all vararg arguments.
+ {f(), 5} -- creates a list with the first result from f() and 5.
+
+
+
+
+
+
+
++ +Lua is a lexically scoped language. +The scope of a local variable begins at the first statement after +its declaration and lasts until the last non-void statement +of the innermost block that includes the declaration. +(Void statements are labels and empty statements.) +Consider the following example: + +
+ x = 10 -- global variable + do -- new block + local x = x -- new 'x', with value 10 + print(x) --> 10 + x = x+1 + do -- another block + local x = x+1 -- another 'x' + print(x) --> 12 + end + print(x) --> 11 + end + print(x) --> 10 (the global one) ++ +
+Notice that, in a declaration like local x = x,
+the new x being declared is not in scope yet,
+and so the second x refers to the outside variable.
+
+
+
+Because of the lexical scoping rules, +local variables can be freely accessed by functions +defined inside their scope. +A local variable used by an inner function is called an upvalue +(or external local variable, or simply external variable) +inside the inner function. + + +
+Notice that each execution of a local statement +defines new local variables. +Consider the following example: + +
+ a = {}
+ local x = 20
+ for i = 1, 10 do
+ local y = 0
+ a[i] = function () y = y + 1; return x + y end
+ end
+
+The loop creates ten closures
+(that is, ten instances of the anonymous function).
+Each of these closures uses a different y variable,
+while all of them share the same x.
+
+
+
+
+
+
+
+This section describes the C API for Lua, that is,
+the set of C functions available to the host program to communicate
+with Lua.
+All API functions and related types and constants
+are declared in the header file lua.h.
+
+
+
+Even when we use the term "function", +any facility in the API may be provided as a macro instead. +Except where stated otherwise, +all such macros use each of their arguments exactly once +(except for the first argument, which is always a Lua state), +and so do not generate any hidden side-effects. + + +
+As in most C libraries,
+the Lua API functions do not check their arguments
+for validity or consistency.
+However, you can change this behavior by compiling Lua
+with the macro LUA_USE_APICHECK defined.
+
+
+
+The Lua library is fully reentrant: +it has no global variables. +It keeps all information it needs in a dynamic structure, +called the Lua state. + + +
+Each Lua state has one or more threads,
+which correspond to independent, cooperative lines of execution.
+The type lua_State (despite its name) refers to a thread.
+(Indirectly, through the thread, it also refers to the
+Lua state associated to the thread.)
+
+
+
+A pointer to a thread must be passed as the first argument to
+every function in the library, except to lua_newstate,
+which creates a Lua state from scratch and returns a pointer
+to the main thread in the new state.
+
+
+
+
+
+
+Lua uses a virtual stack to pass values to and from C. +Each element in this stack represents a Lua value +(nil, number, string, etc.). +Functions in the API can access this stack through the +Lua state parameter that they receive. + + +
+Whenever Lua calls C, the called function gets a new stack,
+which is independent of previous stacks and of stacks of
+C functions that are still active.
+This stack initially contains any arguments to the C function
+and it is where the C function can store temporary
+Lua values and must push its results
+to be returned to the caller (see lua_CFunction).
+
+
+
+For convenience, +most query operations in the API do not follow a strict stack discipline. +Instead, they can refer to any element in the stack +by using an index: +A positive index represents an absolute stack position, +starting at 1 as the bottom of the stack; +a negative index represents an offset relative to the top of the stack. +More specifically, if the stack has n elements, +then index 1 represents the first element +(that is, the element that was pushed onto the stack first) +and +index n represents the last element; +index -1 also represents the last element +(that is, the element at the top) +and index -n represents the first element. + + + + + +
+When you interact with the Lua API, +you are responsible for ensuring consistency. +In particular, +you are responsible for controlling stack overflow. +When you call any API function, +you must ensure the stack has enough room to accommodate the results. + + +
+There is one exception to the above rule:
+When you call a Lua function
+without a fixed number of results (see lua_call),
+Lua ensures that the stack has enough space for all results.
+However, it does not ensure any extra space.
+So, before pushing anything on the stack after such a call
+you should use lua_checkstack.
+
+
+
+Whenever Lua calls C,
+it ensures that the stack has space for
+at least LUA_MINSTACK extra elements;
+that is, you can safely push up to LUA_MINSTACK values into it.
+LUA_MINSTACK is defined as 20,
+so that usually you do not have to worry about stack space
+unless your code has loops pushing elements onto the stack.
+Whenever necessary,
+you can use the function lua_checkstack
+to ensure that the stack has enough space for pushing new elements.
+
+
+
+
+
+
+Any function in the API that receives stack indices +works only with valid indices or acceptable indices. + + +
+A valid index is an index that refers to a
+position that stores a modifiable Lua value.
+It comprises stack indices between 1 and the stack top
+(1 ≤ abs(index) ≤ top)
+
+plus pseudo-indices,
+which represent some positions that are accessible to C code
+but that are not in the stack.
+Pseudo-indices are used to access the registry (see §4.3)
+and the upvalues of a C function (see §4.2).
+
+
+
+Functions that do not need a specific mutable position, +but only a value (e.g., query functions), +can be called with acceptable indices. +An acceptable index can be any valid index, +but it also can be any positive index after the stack top +within the space allocated for the stack, +that is, indices up to the stack size. +(Note that 0 is never an acceptable index.) +Indices to upvalues (see §4.2) greater than the real number +of upvalues in the current C function are also acceptable (but invalid). +Except when noted otherwise, +functions in the API work with acceptable indices. + + +
+Acceptable indices serve to avoid extra tests +against the stack top when querying the stack. +For instance, a C function can query its third argument +without the need to check whether there is a third argument, +that is, without the need to check whether 3 is a valid index. + + +
+For functions that can be called with acceptable indices,
+any non-valid index is treated as if it
+contains a value of a virtual type LUA_TNONE,
+which behaves like a nil value.
+
+
+
+
+
+
+Several functions in the API return pointers (const char*)
+to Lua strings in the stack.
+(See lua_pushfstring, lua_pushlstring,
+lua_pushstring, and lua_tolstring.
+See also luaL_checklstring, luaL_checkstring,
+and luaL_tolstring in the auxiliary library.)
+
+
+
+In general, +Lua's garbage collection can free or move internal memory +and then invalidate pointers to internal strings. +To allow a safe use of these pointers, +the API guarantees that any pointer to a string in a stack index +is valid while the string value at that index is not removed from the stack. +(It can be moved to another index, though.) +When the index is a pseudo-index (referring to an upvalue), +the pointer is valid while the corresponding call is active and +the corresponding upvalue is not modified. + + +
+Some functions in the debug interface
+also return pointers to strings,
+namely lua_getlocal, lua_getupvalue,
+lua_setlocal, and lua_setupvalue.
+For these functions, the pointer is guaranteed to
+be valid while the caller function is active and
+the given closure (if one was given) is in the stack.
+
+
+
+Except for these guarantees, +the garbage collector is free to invalidate +any pointer to internal strings. + + + + + + + +
+When a C function is created,
+it is possible to associate some values with it,
+thus creating a C closure
+(see lua_pushcclosure);
+these values are called upvalues and are
+accessible to the function whenever it is called.
+
+
+
+Whenever a C function is called,
+its upvalues are located at specific pseudo-indices.
+These pseudo-indices are produced by the macro
+lua_upvalueindex.
+The first upvalue associated with a function is at index
+lua_upvalueindex(1), and so on.
+Any access to lua_upvalueindex(n),
+where n is greater than the number of upvalues of the
+current function
+(but not greater than 256,
+which is one plus the maximum number of upvalues in a closure),
+produces an acceptable but invalid index.
+
+
+
+A C closure can also change the values +of its corresponding upvalues. + + + + + +
+Lua provides a registry,
+a predefined table that can be used by any C code to
+store whatever Lua values it needs to store.
+The registry table is always accessible at pseudo-index
+LUA_REGISTRYINDEX.
+Any C library can store data into this table,
+but it must take care to choose keys
+that are different from those used
+by other libraries, to avoid collisions.
+Typically, you should use as key a string containing your library name,
+or a light userdata with the address of a C object in your code,
+or any Lua object created by your code.
+As with variable names,
+string keys starting with an underscore followed by
+uppercase letters are reserved for Lua.
+
+
+
+The integer keys in the registry are used
+by the reference mechanism (see luaL_ref)
+and by some predefined values.
+Therefore, integer keys in the registry
+must not be used for other purposes.
+
+
+
+When you create a new Lua state,
+its registry comes with some predefined values.
+These predefined values are indexed with integer keys
+defined as constants in lua.h.
+The following constants are defined:
+
+
LUA_RIDX_MAINTHREAD: At this index the registry has
+the main thread of the state.
+(The main thread is the one created together with the state.)
+LUA_RIDX_GLOBALS: At this index the registry has
+the global environment.
+
+Internally, Lua uses the C longjmp facility to handle errors.
+(Lua will use exceptions if you compile it as C++;
+search for LUAI_THROW in the source code for details.)
+When Lua faces any error,
+such as a memory allocation error or a type error,
+it raises an error;
+that is, it does a long jump.
+A protected environment uses setjmp
+to set a recovery point;
+any error jumps to the most recent active recovery point.
+
+
+
+Inside a C function you can raise an error explicitly
+by calling lua_error.
+
+
+
+Most functions in the API can raise an error, +for instance due to a memory allocation error. +The documentation for each function indicates whether +it can raise errors. + + +
+If an error happens outside any protected environment,
+Lua calls a panic function (see lua_atpanic)
+and then calls abort,
+thus exiting the host application.
+Your panic function can avoid this exit by
+never returning
+(e.g., doing a long jump to your own recovery point outside Lua).
+
+
+
+The panic function,
+as its name implies,
+is a mechanism of last resort.
+Programs should avoid it.
+As a general rule,
+when a C function is called by Lua with a Lua state,
+it can do whatever it wants on that Lua state,
+as it should be already protected.
+However,
+when C code operates on other Lua states
+(e.g., a Lua-state argument to the function,
+a Lua state stored in the registry, or
+the result of lua_newthread),
+it should use them only in API calls that cannot raise errors.
+
+
+
+The panic function runs as if it were a message handler (see §2.3); +in particular, the error object is on the top of the stack. +However, there is no guarantee about stack space. +To push anything on the stack, +the panic function must first check the available space (see §4.1.1). + + + + + +
+Several functions that report errors in the API use the following +status codes to indicate different kinds of errors or other conditions: + +
LUA_OK (0): no errors.LUA_ERRRUN: a runtime error.LUA_ERRMEM:
+memory allocation error.
+For such errors, Lua does not call the message handler.
+LUA_ERRERR: error while running the message handler.LUA_ERRSYNTAX: syntax error during precompilation.LUA_YIELD: the thread (coroutine) yields.LUA_ERRFILE: a file-related error;
+e.g., it cannot open or read the file.
+These constants are defined in the header file lua.h.
+
+
+
+
+
+
+
+
+Internally, Lua uses the C longjmp facility to yield a coroutine.
+Therefore, if a C function foo calls an API function
+and this API function yields
+(directly or indirectly by calling another function that yields),
+Lua cannot return to foo any more,
+because the longjmp removes its frame from the C stack.
+
+
+
+To avoid this kind of problem,
+Lua raises an error whenever it tries to yield across an API call,
+except for three functions:
+lua_yieldk, lua_callk, and lua_pcallk.
+All those functions receive a continuation function
+(as a parameter named k) to continue execution after a yield.
+
+
+
+We need to set some terminology to explain continuations.
+We have a C function called from Lua which we will call
+the original function.
+This original function then calls one of those three functions in the C API,
+which we will call the callee function,
+that then yields the current thread.
+This can happen when the callee function is lua_yieldk,
+or when the callee function is either lua_callk or lua_pcallk
+and the function called by them yields.
+
+
+
+Suppose the running thread yields while executing the callee function. +After the thread resumes, +it eventually will finish running the callee function. +However, +the callee function cannot return to the original function, +because its frame in the C stack was destroyed by the yield. +Instead, Lua calls a continuation function, +which was given as an argument to the callee function. +As the name implies, +the continuation function should continue the task +of the original function. + + +
+As an illustration, consider the following function: + +
+ int original_function (lua_State *L) {
+ ... /* code 1 */
+ status = lua_pcall(L, n, m, h); /* calls Lua */
+ ... /* code 2 */
+ }
+
+Now we want to allow
+the Lua code being run by lua_pcall to yield.
+First, we can rewrite our function like here:
+
+
+ int k (lua_State *L, int status, lua_KContext ctx) {
+ ... /* code 2 */
+ }
+
+ int original_function (lua_State *L) {
+ ... /* code 1 */
+ return k(L, lua_pcall(L, n, m, h), ctx);
+ }
+
+In the above code,
+the new function k is a
+continuation function (with type lua_KFunction),
+which should do all the work that the original function
+was doing after calling lua_pcall.
+Now, we must inform Lua that it must call k if the Lua code
+being executed by lua_pcall gets interrupted in some way
+(errors or yielding),
+so we rewrite the code as here,
+replacing lua_pcall by lua_pcallk:
+
+
+ int original_function (lua_State *L) {
+ ... /* code 1 */
+ return k(L, lua_pcallk(L, n, m, h, ctx2, k), ctx1);
+ }
+
+Note the external, explicit call to the continuation:
+Lua will call the continuation only if needed, that is,
+in case of errors or resuming after a yield.
+If the called function returns normally without ever yielding,
+lua_pcallk (and lua_callk) will also return normally.
+(Of course, instead of calling the continuation in that case,
+you can do the equivalent work directly inside the original function.)
+
+
+
+Besides the Lua state,
+the continuation function has two other parameters:
+the final status of the call and the context value (ctx) that
+was passed originally to lua_pcallk.
+Lua does not use this context value;
+it only passes this value from the original function to the
+continuation function.
+For lua_pcallk,
+the status is the same value that would be returned by lua_pcallk,
+except that it is LUA_YIELD when being executed after a yield
+(instead of LUA_OK).
+For lua_yieldk and lua_callk,
+the status is always LUA_YIELD when Lua calls the continuation.
+(For these two functions,
+Lua will not call the continuation in case of errors,
+because they do not handle errors.)
+Similarly, when using lua_callk,
+you should call the continuation function
+with LUA_OK as the status.
+(For lua_yieldk, there is not much point in calling
+directly the continuation function,
+because lua_yieldk usually does not return.)
+
+
+
+Lua treats the continuation function as if it were the original function.
+The continuation function receives the same Lua stack
+from the original function,
+in the same state it would be if the callee function had returned.
+(For instance,
+after a lua_callk the function and its arguments are
+removed from the stack and replaced by the results from the call.)
+It also has the same upvalues.
+Whatever it returns is handled by Lua as if it were the return
+of the original function.
+
+
+
+
+
+
+Here we list all functions and types from the C API in +alphabetical order. +Each function has an indicator like this: +[-o, +p, x] + + +
+The first field, o,
+is how many elements the function pops from the stack.
+The second field, p,
+is how many elements the function pushes onto the stack.
+(Any function always pushes its results after popping its arguments.)
+A field in the form x|y means the function can push (or pop)
+x or y elements,
+depending on the situation;
+an interrogation mark '?' means that
+we cannot know how many elements the function pops/pushes
+by looking only at its arguments.
+(For instance, they may depend on what is in the stack.)
+The third field, x,
+tells whether the function may raise errors:
+'-' means the function never raises any error;
+'m' means the function may raise only out-of-memory errors;
+'v' means the function may raise the errors explained in the text;
+'e' means the function can run arbitrary Lua code,
+either directly or through metamethods,
+and therefore may raise any errors.
+
+
+
+
lua_absindex+[-0, +0, –] +
int lua_absindex (lua_State *L, int idx);+ +
+Converts the acceptable index idx
+into an equivalent absolute index
+(that is, one that does not depend on the stack size).
+
+
+
+
+
+
lua_Alloctypedef void * (*lua_Alloc) (void *ud, + void *ptr, + size_t osize, + size_t nsize);+ +
+The type of the memory-allocation function used by Lua states.
+The allocator function must provide a
+functionality similar to realloc,
+but not exactly the same.
+Its arguments are
+ud, an opaque pointer passed to lua_newstate;
+ptr, a pointer to the block being allocated/reallocated/freed;
+osize, the original size of the block or some code about what
+is being allocated;
+and nsize, the new size of the block.
+
+
+
+When ptr is not NULL,
+osize is the size of the block pointed by ptr,
+that is, the size given when it was allocated or reallocated.
+
+
+
+When ptr is NULL,
+osize encodes the kind of object that Lua is allocating.
+osize is any of
+LUA_TSTRING, LUA_TTABLE, LUA_TFUNCTION,
+LUA_TUSERDATA, or LUA_TTHREAD when (and only when)
+Lua is creating a new object of that type.
+When osize is some other value,
+Lua is allocating memory for something else.
+
+
+
+Lua assumes the following behavior from the allocator function: + + +
+When nsize is zero,
+the allocator must behave like free
+and then return NULL.
+
+
+
+When nsize is not zero,
+the allocator must behave like realloc.
+In particular, the allocator returns NULL
+if and only if it cannot fulfill the request.
+
+
+
+Here is a simple implementation for the allocator function.
+It is used in the auxiliary library by luaL_newstate.
+
+
+ static void *l_alloc (void *ud, void *ptr, size_t osize,
+ size_t nsize) {
+ (void)ud; (void)osize; /* not used */
+ if (nsize == 0) {
+ free(ptr);
+ return NULL;
+ }
+ else
+ return realloc(ptr, nsize);
+ }
+
+Note that ISO C ensures
+that free(NULL) has no effect and that
+realloc(NULL,size) is equivalent to malloc(size).
+
+
+
+
+
+
lua_arith+[-(2|1), +1, e] +
void lua_arith (lua_State *L, int op);+ +
+Performs an arithmetic or bitwise operation over the two values +(or one, in the case of negations) +at the top of the stack, +with the value on the top being the second operand, +pops these values, and pushes the result of the operation. +The function follows the semantics of the corresponding Lua operator +(that is, it may call metamethods). + + +
+The value of op must be one of the following constants:
+
+
LUA_OPADD: performs addition (+)LUA_OPSUB: performs subtraction (-)LUA_OPMUL: performs multiplication (*)LUA_OPDIV: performs float division (/)LUA_OPIDIV: performs floor division (//)LUA_OPMOD: performs modulo (%)LUA_OPPOW: performs exponentiation (^)LUA_OPUNM: performs mathematical negation (unary -)LUA_OPBNOT: performs bitwise NOT (~)LUA_OPBAND: performs bitwise AND (&)LUA_OPBOR: performs bitwise OR (|)LUA_OPBXOR: performs bitwise exclusive OR (~)LUA_OPSHL: performs left shift (<<)LUA_OPSHR: performs right shift (>>)lua_atpanic+[-0, +0, –] +
lua_CFunction lua_atpanic (lua_State *L, lua_CFunction panicf);+ +
+Sets a new panic function and returns the old one (see §4.4). + + + + + +
lua_call+[-(nargs+1), +nresults, e] +
void lua_call (lua_State *L, int nargs, int nresults);+ +
+Calls a function.
+Like regular Lua calls,
+lua_call respects the __call metamethod.
+So, here the word "function"
+means any callable value.
+
+
+
+To do a call you must use the following protocol:
+first, the function to be called is pushed onto the stack;
+then, the arguments to the call are pushed
+in direct order;
+that is, the first argument is pushed first.
+Finally you call lua_call;
+nargs is the number of arguments that you pushed onto the stack.
+When the function returns,
+all arguments and the function value are popped
+and the call results are pushed onto the stack.
+The number of results is adjusted to nresults,
+unless nresults is LUA_MULTRET.
+In this case, all results from the function are pushed;
+Lua takes care that the returned values fit into the stack space,
+but it does not ensure any extra space in the stack.
+The function results are pushed onto the stack in direct order
+(the first result is pushed first),
+so that after the call the last result is on the top of the stack.
+
+
+
+Any error while calling and running the function is propagated upwards
+(with a longjmp).
+
+
+
+The following example shows how the host program can do the +equivalent to this Lua code: + +
+ a = f("how", t.x, 14)
++Here it is in C: + +
+ lua_getglobal(L, "f"); /* function to be called */ + lua_pushliteral(L, "how"); /* 1st argument */ + lua_getglobal(L, "t"); /* table to be indexed */ + lua_getfield(L, -1, "x"); /* push result of t.x (2nd arg) */ + lua_remove(L, -2); /* remove 't' from the stack */ + lua_pushinteger(L, 14); /* 3rd argument */ + lua_call(L, 3, 1); /* call 'f' with 3 arguments and 1 result */ + lua_setglobal(L, "a"); /* set global 'a' */ +
+Note that the code above is balanced: +at its end, the stack is back to its original configuration. +This is considered good programming practice. + + + + + +
lua_callk+[-(nargs + 1), +nresults, e] +
void lua_callk (lua_State *L, + int nargs, + int nresults, + lua_KContext ctx, + lua_KFunction k);+ +
+This function behaves exactly like lua_call,
+but allows the called function to yield (see §4.5).
+
+
+
+
+
+
lua_CFunctiontypedef int (*lua_CFunction) (lua_State *L);+ +
+Type for C functions. + + +
+In order to communicate properly with Lua,
+a C function must use the following protocol,
+which defines the way parameters and results are passed:
+a C function receives its arguments from Lua in its stack
+in direct order (the first argument is pushed first).
+So, when the function starts,
+lua_gettop(L) returns the number of arguments received by the function.
+The first argument (if any) is at index 1
+and its last argument is at index lua_gettop(L).
+To return values to Lua, a C function just pushes them onto the stack,
+in direct order (the first result is pushed first),
+and returns in C the number of results.
+Any other value in the stack below the results will be properly
+discarded by Lua.
+Like a Lua function, a C function called by Lua can also return
+many results.
+
+
+
+As an example, the following function receives a variable number +of numeric arguments and returns their average and their sum: + +
+ static int foo (lua_State *L) {
+ int n = lua_gettop(L); /* number of arguments */
+ lua_Number sum = 0.0;
+ int i;
+ for (i = 1; i <= n; i++) {
+ if (!lua_isnumber(L, i)) {
+ lua_pushliteral(L, "incorrect argument");
+ lua_error(L);
+ }
+ sum += lua_tonumber(L, i);
+ }
+ lua_pushnumber(L, sum/n); /* first result */
+ lua_pushnumber(L, sum); /* second result */
+ return 2; /* number of results */
+ }
+
+
+
+
+
+lua_checkstack+[-0, +0, –] +
int lua_checkstack (lua_State *L, int n);+ +
+Ensures that the stack has space for at least n extra elements,
+that is, that you can safely push up to n values into it.
+It returns false if it cannot fulfill the request,
+either because it would cause the stack
+to be greater than a fixed maximum size
+(typically at least several thousand elements) or
+because it cannot allocate memory for the extra space.
+This function never shrinks the stack;
+if the stack already has space for the extra elements,
+it is left unchanged.
+
+
+
+
+
+
lua_close+[-0, +0, –] +
void lua_close (lua_State *L);+ +
+Close all active to-be-closed variables in the main thread, +release all objects in the given Lua state +(calling the corresponding garbage-collection metamethods, if any), +and frees all dynamic memory used by this state. + + +
+On several platforms, you may not need to call this function, +because all resources are naturally released when the host program ends. +On the other hand, long-running programs that create multiple states, +such as daemons or web servers, +will probably need to close states as soon as they are not needed. + + + + + +
lua_closeslot+[-0, +0, e] +
void lua_closeslot (lua_State *L, int index);+ +
+Close the to-be-closed slot at the given index and set its value to nil.
+The index must be the last index previously marked to be closed
+(see lua_toclose) that is still active (that is, not closed yet).
+
+
+
+A __close metamethod cannot yield
+when called through this function.
+
+
+
+(This function was introduced in release 5.4.3.) + + + + + +
lua_closethread+[-0, +?, –] +
int lua_closethread (lua_State *L, lua_State *from);+ +
+Resets a thread, cleaning its call stack and closing all pending
+to-be-closed variables.
+Returns a status code:
+LUA_OK for no errors in the thread
+(either the original error that stopped the thread or
+errors in closing methods),
+or an error status otherwise.
+In case of error,
+leaves the error object on the top of the stack.
+
+
+
+The parameter from represents the coroutine that is resetting L.
+If there is no such coroutine,
+this parameter can be NULL.
+
+
+
+(This function was introduced in release 5.4.6.) + + + + + +
lua_compare+[-0, +0, e] +
int lua_compare (lua_State *L, int index1, int index2, int op);+ +
+Compares two Lua values.
+Returns 1 if the value at index index1 satisfies op
+when compared with the value at index index2,
+following the semantics of the corresponding Lua operator
+(that is, it may call metamethods).
+Otherwise returns 0.
+Also returns 0 if any of the indices is not valid.
+
+
+
+The value of op must be one of the following constants:
+
+
LUA_OPEQ: compares for equality (==)LUA_OPLT: compares for less than (<)LUA_OPLE: compares for less or equal (<=)lua_concat+[-n, +1, e] +
void lua_concat (lua_State *L, int n);+ +
+Concatenates the n values at the top of the stack,
+pops them, and leaves the result on the top.
+If n is 1, the result is the single value on the stack
+(that is, the function does nothing);
+if n is 0, the result is the empty string.
+Concatenation is performed following the usual semantics of Lua
+(see §3.4.6).
+
+
+
+
+
+
lua_copy+[-0, +0, –] +
void lua_copy (lua_State *L, int fromidx, int toidx);+ +
+Copies the element at index fromidx
+into the valid index toidx,
+replacing the value at that position.
+Values at other positions are not affected.
+
+
+
+
+
+
lua_createtable+[-0, +1, m] +
void lua_createtable (lua_State *L, int narr, int nrec);+ +
+Creates a new empty table and pushes it onto the stack.
+Parameter narr is a hint for how many elements the table
+will have as a sequence;
+parameter nrec is a hint for how many other elements
+the table will have.
+Lua may use these hints to preallocate memory for the new table.
+This preallocation may help performance when you know in advance
+how many elements the table will have.
+Otherwise you can use the function lua_newtable.
+
+
+
+
+
+
lua_dump+[-0, +0, –] +
int lua_dump (lua_State *L, + lua_Writer writer, + void *data, + int strip);+ +
+Dumps a function as a binary chunk.
+Receives a Lua function on the top of the stack
+and produces a binary chunk that,
+if loaded again,
+results in a function equivalent to the one dumped.
+As it produces parts of the chunk,
+lua_dump calls function writer (see lua_Writer)
+with the given data
+to write them.
+
+
+
+If strip is true,
+the binary representation may not include all debug information
+about the function,
+to save space.
+
+
+
+The value returned is the error code returned by the last +call to the writer; +0 means no errors. + + +
+This function does not pop the Lua function from the stack. + + + + + +
lua_error+[-1, +0, v] +
int lua_error (lua_State *L);+ +
+Raises a Lua error,
+using the value on the top of the stack as the error object.
+This function does a long jump,
+and therefore never returns
+(see luaL_error).
+
+
+
+
+
+
lua_gc+[-0, +0, –] +
int lua_gc (lua_State *L, int what, ...);+ +
+Controls the garbage collector. + + +
+This function performs several tasks,
+according to the value of the parameter what.
+For options that need extra arguments,
+they are listed after the option.
+
+
LUA_GCCOLLECT:
+Performs a full garbage-collection cycle.
+LUA_GCSTOP:
+Stops the garbage collector.
+LUA_GCRESTART:
+Restarts the garbage collector.
+LUA_GCCOUNT:
+Returns the current amount of memory (in Kbytes) in use by Lua.
+LUA_GCCOUNTB:
+Returns the remainder of dividing the current amount of bytes of
+memory in use by Lua by 1024.
+LUA_GCSTEP (int stepsize):
+Performs an incremental step of garbage collection,
+corresponding to the allocation of stepsize Kbytes.
+LUA_GCISRUNNING:
+Returns a boolean that tells whether the collector is running
+(i.e., not stopped).
+LUA_GCINC (int pause, int stepmul, stepsize):
+Changes the collector to incremental mode
+with the given parameters (see §2.5.1).
+Returns the previous mode (LUA_GCGEN or LUA_GCINC).
+LUA_GCGEN (int minormul, int majormul):
+Changes the collector to generational mode
+with the given parameters (see §2.5.2).
+Returns the previous mode (LUA_GCGEN or LUA_GCINC).
+
+For more details about these options,
+see collectgarbage.
+
+
+
+This function should not be called by a finalizer. + + + + + +
lua_getallocf+[-0, +0, –] +
lua_Alloc lua_getallocf (lua_State *L, void **ud);+ +
+Returns the memory-allocation function of a given state.
+If ud is not NULL, Lua stores in *ud the
+opaque pointer given when the memory-allocator function was set.
+
+
+
+
+
+
lua_getfield+[-0, +1, e] +
int lua_getfield (lua_State *L, int index, const char *k);+ +
+Pushes onto the stack the value t[k],
+where t is the value at the given index.
+As in Lua, this function may trigger a metamethod
+for the "index" event (see §2.4).
+
+
+
+Returns the type of the pushed value. + + + + + +
lua_getextraspace+[-0, +0, –] +
void *lua_getextraspace (lua_State *L);+ +
+Returns a pointer to a raw memory area associated with the +given Lua state. +The application can use this area for any purpose; +Lua does not use it for anything. + + +
+Each new thread has this area initialized with a copy +of the area of the main thread. + + +
+By default, this area has the size of a pointer to void,
+but you can recompile Lua with a different size for this area.
+(See LUA_EXTRASPACE in luaconf.h.)
+
+
+
+
+
+
lua_getglobal+[-0, +1, e] +
int lua_getglobal (lua_State *L, const char *name);+ +
+Pushes onto the stack the value of the global name.
+Returns the type of that value.
+
+
+
+
+
+
lua_geti+[-0, +1, e] +
int lua_geti (lua_State *L, int index, lua_Integer i);+ +
+Pushes onto the stack the value t[i],
+where t is the value at the given index.
+As in Lua, this function may trigger a metamethod
+for the "index" event (see §2.4).
+
+
+
+Returns the type of the pushed value. + + + + + +
lua_getmetatable+[-0, +(0|1), –] +
int lua_getmetatable (lua_State *L, int index);+ +
+If the value at the given index has a metatable, +the function pushes that metatable onto the stack and returns 1. +Otherwise, +the function returns 0 and pushes nothing on the stack. + + + + + +
lua_gettable+[-1, +1, e] +
int lua_gettable (lua_State *L, int index);+ +
+Pushes onto the stack the value t[k],
+where t is the value at the given index
+and k is the value on the top of the stack.
+
+
+
+This function pops the key from the stack, +pushing the resulting value in its place. +As in Lua, this function may trigger a metamethod +for the "index" event (see §2.4). + + +
+Returns the type of the pushed value. + + + + + +
lua_gettop+[-0, +0, –] +
int lua_gettop (lua_State *L);+ +
+Returns the index of the top element in the stack. +Because indices start at 1, +this result is equal to the number of elements in the stack; +in particular, 0 means an empty stack. + + + + + +
lua_getiuservalue+[-0, +1, –] +
int lua_getiuservalue (lua_State *L, int index, int n);+ +
+Pushes onto the stack the n-th user value associated with the
+full userdata at the given index and
+returns the type of the pushed value.
+
+
+
+If the userdata does not have that value,
+pushes nil and returns LUA_TNONE.
+
+
+
+
+
+
lua_insert+[-1, +1, –] +
void lua_insert (lua_State *L, int index);+ +
+Moves the top element into the given valid index, +shifting up the elements above this index to open space. +This function cannot be called with a pseudo-index, +because a pseudo-index is not an actual stack position. + + + + + +
lua_Integertypedef ... lua_Integer;+ +
+The type of integers in Lua. + + +
+By default this type is long long,
+(usually a 64-bit two-complement integer),
+but that can be changed to long or int
+(usually a 32-bit two-complement integer).
+(See LUA_INT_TYPE in luaconf.h.)
+
+
+
+Lua also defines the constants
+LUA_MININTEGER and LUA_MAXINTEGER,
+with the minimum and the maximum values that fit in this type.
+
+
+
+
+
+
lua_isboolean+[-0, +0, –] +
int lua_isboolean (lua_State *L, int index);+ +
+Returns 1 if the value at the given index is a boolean, +and 0 otherwise. + + + + + +
lua_iscfunction+[-0, +0, –] +
int lua_iscfunction (lua_State *L, int index);+ +
+Returns 1 if the value at the given index is a C function, +and 0 otherwise. + + + + + +
lua_isfunction+[-0, +0, –] +
int lua_isfunction (lua_State *L, int index);+ +
+Returns 1 if the value at the given index is a function +(either C or Lua), and 0 otherwise. + + + + + +
lua_isinteger+[-0, +0, –] +
int lua_isinteger (lua_State *L, int index);+ +
+Returns 1 if the value at the given index is an integer +(that is, the value is a number and is represented as an integer), +and 0 otherwise. + + + + + +
lua_islightuserdata+[-0, +0, –] +
int lua_islightuserdata (lua_State *L, int index);+ +
+Returns 1 if the value at the given index is a light userdata, +and 0 otherwise. + + + + + +
lua_isnil+[-0, +0, –] +
int lua_isnil (lua_State *L, int index);+ +
+Returns 1 if the value at the given index is nil, +and 0 otherwise. + + + + + +
lua_isnone+[-0, +0, –] +
int lua_isnone (lua_State *L, int index);+ +
+Returns 1 if the given index is not valid, +and 0 otherwise. + + + + + +
lua_isnoneornil+[-0, +0, –] +
int lua_isnoneornil (lua_State *L, int index);+ +
+Returns 1 if the given index is not valid +or if the value at this index is nil, +and 0 otherwise. + + + + + +
lua_isnumber+[-0, +0, –] +
int lua_isnumber (lua_State *L, int index);+ +
+Returns 1 if the value at the given index is a number +or a string convertible to a number, +and 0 otherwise. + + + + + +
lua_isstring+[-0, +0, –] +
int lua_isstring (lua_State *L, int index);+ +
+Returns 1 if the value at the given index is a string +or a number (which is always convertible to a string), +and 0 otherwise. + + + + + +
lua_istable+[-0, +0, –] +
int lua_istable (lua_State *L, int index);+ +
+Returns 1 if the value at the given index is a table, +and 0 otherwise. + + + + + +
lua_isthread+[-0, +0, –] +
int lua_isthread (lua_State *L, int index);+ +
+Returns 1 if the value at the given index is a thread, +and 0 otherwise. + + + + + +
lua_isuserdata+[-0, +0, –] +
int lua_isuserdata (lua_State *L, int index);+ +
+Returns 1 if the value at the given index is a userdata +(either full or light), and 0 otherwise. + + + + + +
lua_isyieldable+[-0, +0, –] +
int lua_isyieldable (lua_State *L);+ +
+Returns 1 if the given coroutine can yield, +and 0 otherwise. + + + + + +
lua_KContexttypedef ... lua_KContext;+ +
+The type for continuation-function contexts.
+It must be a numeric type.
+This type is defined as intptr_t
+when intptr_t is available,
+so that it can store pointers too.
+Otherwise, it is defined as ptrdiff_t.
+
+
+
+
+
+
lua_KFunctiontypedef int (*lua_KFunction) (lua_State *L, int status, lua_KContext ctx);+ +
+Type for continuation functions (see §4.5). + + + + + +
lua_len+[-0, +1, e] +
void lua_len (lua_State *L, int index);+ +
+Returns the length of the value at the given index.
+It is equivalent to the '#' operator in Lua (see §3.4.7) and
+may trigger a metamethod for the "length" event (see §2.4).
+The result is pushed on the stack.
+
+
+
+
+
+
lua_load+[-0, +1, –] +
int lua_load (lua_State *L, + lua_Reader reader, + void *data, + const char *chunkname, + const char *mode);+ +
+Loads a Lua chunk without running it.
+If there are no errors,
+lua_load pushes the compiled chunk as a Lua
+function on top of the stack.
+Otherwise, it pushes an error message.
+
+
+
+The lua_load function uses a user-supplied reader function
+to read the chunk (see lua_Reader).
+The data argument is an opaque value passed to the reader function.
+
+
+
+The chunkname argument gives a name to the chunk,
+which is used for error messages and in debug information (see §4.7).
+
+
+
+lua_load automatically detects whether the chunk is text or binary
+and loads it accordingly (see program luac).
+The string mode works as in function load,
+with the addition that
+a NULL value is equivalent to the string "bt".
+
+
+
+lua_load uses the stack internally,
+so the reader function must always leave the stack
+unmodified when returning.
+
+
+
+lua_load can return
+LUA_OK, LUA_ERRSYNTAX, or LUA_ERRMEM.
+The function may also return other values corresponding to
+errors raised by the read function (see §4.4.1).
+
+
+
+If the resulting function has upvalues,
+its first upvalue is set to the value of the global environment
+stored at index LUA_RIDX_GLOBALS in the registry (see §4.3).
+When loading main chunks,
+this upvalue will be the _ENV variable (see §2.2).
+Other upvalues are initialized with nil.
+
+
+
+
+
+
lua_newstate+[-0, +0, –] +
lua_State *lua_newstate (lua_Alloc f, void *ud);+ +
+Creates a new independent state and returns its main thread.
+Returns NULL if it cannot create the state
+(due to lack of memory).
+The argument f is the allocator function;
+Lua will do all memory allocation for this state
+through this function (see lua_Alloc).
+The second argument, ud, is an opaque pointer that Lua
+passes to the allocator in every call.
+
+
+
+
+
+
lua_newtable+[-0, +1, m] +
void lua_newtable (lua_State *L);+ +
+Creates a new empty table and pushes it onto the stack.
+It is equivalent to lua_createtable(L, 0, 0).
+
+
+
+
+
+
lua_newthread+[-0, +1, m] +
lua_State *lua_newthread (lua_State *L);+ +
+Creates a new thread, pushes it on the stack,
+and returns a pointer to a lua_State that represents this new thread.
+The new thread returned by this function shares with the original thread
+its global environment,
+but has an independent execution stack.
+
+
+
+Threads are subject to garbage collection, +like any Lua object. + + + + + +
lua_newuserdatauv+[-0, +1, m] +
void *lua_newuserdatauv (lua_State *L, size_t size, int nuvalue);+ +
+This function creates and pushes on the stack a new full userdata,
+with nuvalue associated Lua values, called user values,
+plus an associated block of raw memory with size bytes.
+(The user values can be set and read with the functions
+lua_setiuservalue and lua_getiuservalue.)
+
+
+
+The function returns the address of the block of memory. +Lua ensures that this address is valid as long as +the corresponding userdata is alive (see §2.5). +Moreover, if the userdata is marked for finalization (see §2.5.3), +its address is valid at least until the call to its finalizer. + + + + + +
lua_next+[-1, +(2|0), v] +
int lua_next (lua_State *L, int index);+ +
+Pops a key from the stack,
+and pushes a key–value pair from the table at the given index,
+the "next" pair after the given key.
+If there are no more elements in the table,
+then lua_next returns 0 and pushes nothing.
+
+
+
+A typical table traversal looks like this: + +
+ /* table is in the stack at index 't' */
+ lua_pushnil(L); /* first key */
+ while (lua_next(L, t) != 0) {
+ /* uses 'key' (at index -2) and 'value' (at index -1) */
+ printf("%s - %s\n",
+ lua_typename(L, lua_type(L, -2)),
+ lua_typename(L, lua_type(L, -1)));
+ /* removes 'value'; keeps 'key' for next iteration */
+ lua_pop(L, 1);
+ }
+
+
+
+While traversing a table,
+avoid calling lua_tolstring directly on a key,
+unless you know that the key is actually a string.
+Recall that lua_tolstring may change
+the value at the given index;
+this confuses the next call to lua_next.
+
+
+
+This function may raise an error if the given key
+is neither nil nor present in the table.
+See function next for the caveats of modifying
+the table during its traversal.
+
+
+
+
+
+
lua_Numbertypedef ... lua_Number;+ +
+The type of floats in Lua. + + +
+By default this type is double,
+but that can be changed to a single float or a long double.
+(See LUA_FLOAT_TYPE in luaconf.h.)
+
+
+
+
+
+
lua_numbertointegerint lua_numbertointeger (lua_Number n, lua_Integer *p);+ +
+Tries to convert a Lua float to a Lua integer;
+the float n must have an integral value.
+If that value is within the range of Lua integers,
+it is converted to an integer and assigned to *p.
+The macro results in a boolean indicating whether the
+conversion was successful.
+(Note that this range test can be tricky to do
+correctly without this macro, due to rounding.)
+
+
+
+This macro may evaluate its arguments more than once. + + + + + +
lua_pcall+[-(nargs + 1), +(nresults|1), –] +
int lua_pcall (lua_State *L, int nargs, int nresults, int msgh);+ +
+Calls a function (or a callable object) in protected mode. + + +
+Both nargs and nresults have the same meaning as
+in lua_call.
+If there are no errors during the call,
+lua_pcall behaves exactly like lua_call.
+However, if there is any error,
+lua_pcall catches it,
+pushes a single value on the stack (the error object),
+and returns an error code.
+Like lua_call,
+lua_pcall always removes the function
+and its arguments from the stack.
+
+
+
+If msgh is 0,
+then the error object returned on the stack
+is exactly the original error object.
+Otherwise, msgh is the stack index of a
+message handler.
+(This index cannot be a pseudo-index.)
+In case of runtime errors,
+this handler will be called with the error object
+and its return value will be the object
+returned on the stack by lua_pcall.
+
+
+
+Typically, the message handler is used to add more debug
+information to the error object, such as a stack traceback.
+Such information cannot be gathered after the return of lua_pcall,
+since by then the stack has unwound.
+
+
+
+The lua_pcall function returns one of the following status codes:
+LUA_OK, LUA_ERRRUN, LUA_ERRMEM, or LUA_ERRERR.
+
+
+
+
+
+
lua_pcallk+[-(nargs + 1), +(nresults|1), –] +
int lua_pcallk (lua_State *L, + int nargs, + int nresults, + int msgh, + lua_KContext ctx, + lua_KFunction k);+ +
+This function behaves exactly like lua_pcall,
+except that it allows the called function to yield (see §4.5).
+
+
+
+
+
+
lua_pop+[-n, +0, e] +
void lua_pop (lua_State *L, int n);+ +
+Pops n elements from the stack.
+It is implemented as a macro over lua_settop.
+
+
+
+
+
+
lua_pushboolean+[-0, +1, –] +
void lua_pushboolean (lua_State *L, int b);+ +
+Pushes a boolean value with value b onto the stack.
+
+
+
+
+
+
lua_pushcclosure+[-n, +1, m] +
void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n);+ +
+Pushes a new C closure onto the stack.
+This function receives a pointer to a C function
+and pushes onto the stack a Lua value of type function that,
+when called, invokes the corresponding C function.
+The parameter n tells how many upvalues this function will have
+(see §4.2).
+
+
+
+Any function to be callable by Lua must
+follow the correct protocol to receive its parameters
+and return its results (see lua_CFunction).
+
+
+
+When a C function is created,
+it is possible to associate some values with it,
+the so called upvalues;
+these upvalues are then accessible to the function whenever it is called.
+This association is called a C closure (see §4.2).
+To create a C closure,
+first the initial values for its upvalues must be pushed onto the stack.
+(When there are multiple upvalues, the first value is pushed first.)
+Then lua_pushcclosure
+is called to create and push the C function onto the stack,
+with the argument n telling how many values will be
+associated with the function.
+lua_pushcclosure also pops these values from the stack.
+
+
+
+The maximum value for n is 255.
+
+
+
+When n is zero,
+this function creates a light C function,
+which is just a pointer to the C function.
+In that case, it never raises a memory error.
+
+
+
+
+
+
lua_pushcfunction+[-0, +1, –] +
void lua_pushcfunction (lua_State *L, lua_CFunction f);+ +
+Pushes a C function onto the stack.
+This function is equivalent to lua_pushcclosure with no upvalues.
+
+
+
+
+
+
lua_pushfstring+[-0, +1, v] +
const char *lua_pushfstring (lua_State *L, const char *fmt, ...);+ +
+Pushes onto the stack a formatted string
+and returns a pointer to this string (see §4.1.3).
+It is similar to the ISO C function sprintf,
+but has two important differences.
+First,
+you do not have to allocate space for the result;
+the result is a Lua string and Lua takes care of memory allocation
+(and deallocation, through garbage collection).
+Second,
+the conversion specifiers are quite restricted.
+There are no flags, widths, or precisions.
+The conversion specifiers can only be
+'%%' (inserts the character '%'),
+'%s' (inserts a zero-terminated string, with no size restrictions),
+'%f' (inserts a lua_Number),
+'%I' (inserts a lua_Integer),
+'%p' (inserts a pointer),
+'%d' (inserts an int),
+'%c' (inserts an int as a one-byte character), and
+'%U' (inserts a long int as a UTF-8 byte sequence).
+
+
+
+This function may raise errors due to memory overflow +or an invalid conversion specifier. + + + + + +
lua_pushglobaltable+[-0, +1, –] +
void lua_pushglobaltable (lua_State *L);+ +
+Pushes the global environment onto the stack. + + + + + +
lua_pushinteger+[-0, +1, –] +
void lua_pushinteger (lua_State *L, lua_Integer n);+ +
+Pushes an integer with value n onto the stack.
+
+
+
+
+
+
lua_pushlightuserdata+[-0, +1, –] +
void lua_pushlightuserdata (lua_State *L, void *p);+ +
+Pushes a light userdata onto the stack. + + +
+Userdata represent C values in Lua.
+A light userdata represents a pointer, a void*.
+It is a value (like a number):
+you do not create it, it has no individual metatable,
+and it is not collected (as it was never created).
+A light userdata is equal to "any"
+light userdata with the same C address.
+
+
+
+
+
+
lua_pushliteral+[-0, +1, m] +
const char *lua_pushliteral (lua_State *L, const char *s);+ +
+This macro is equivalent to lua_pushstring,
+but should be used only when s is a literal string.
+(Lua may optimize this case.)
+
+
+
+
+
+
lua_pushlstring+[-0, +1, m] +
const char *lua_pushlstring (lua_State *L, const char *s, size_t len);+ +
+Pushes the string pointed to by s with size len
+onto the stack.
+Lua will make or reuse an internal copy of the given string,
+so the memory at s can be freed or reused immediately after
+the function returns.
+The string can contain any binary data,
+including embedded zeros.
+
+
+
+Returns a pointer to the internal copy of the string (see §4.1.3). + + + + + +
lua_pushnil+[-0, +1, –] +
void lua_pushnil (lua_State *L);+ +
+Pushes a nil value onto the stack. + + + + + +
lua_pushnumber+[-0, +1, –] +
void lua_pushnumber (lua_State *L, lua_Number n);+ +
+Pushes a float with value n onto the stack.
+
+
+
+
+
+
lua_pushstring+[-0, +1, m] +
const char *lua_pushstring (lua_State *L, const char *s);+ +
+Pushes the zero-terminated string pointed to by s
+onto the stack.
+Lua will make or reuse an internal copy of the given string,
+so the memory at s can be freed or reused immediately after
+the function returns.
+
+
+
+Returns a pointer to the internal copy of the string (see §4.1.3). + + +
+If s is NULL, pushes nil and returns NULL.
+
+
+
+
+
+
lua_pushthread+[-0, +1, –] +
int lua_pushthread (lua_State *L);+ +
+Pushes the thread represented by L onto the stack.
+Returns 1 if this thread is the main thread of its state.
+
+
+
+
+
+
lua_pushvalue+[-0, +1, –] +
void lua_pushvalue (lua_State *L, int index);+ +
+Pushes a copy of the element at the given index +onto the stack. + + + + + +
lua_pushvfstring+[-0, +1, v] +
const char *lua_pushvfstring (lua_State *L, + const char *fmt, + va_list argp);+ +
+Equivalent to lua_pushfstring, except that it receives a va_list
+instead of a variable number of arguments.
+
+
+
+
+
+
lua_rawequal+[-0, +0, –] +
int lua_rawequal (lua_State *L, int index1, int index2);+ +
+Returns 1 if the two values in indices index1 and
+index2 are primitively equal
+(that is, equal without calling the __eq metamethod).
+Otherwise returns 0.
+Also returns 0 if any of the indices are not valid.
+
+
+
+
+
+
lua_rawget+[-1, +1, –] +
int lua_rawget (lua_State *L, int index);+ +
+Similar to lua_gettable, but does a raw access
+(i.e., without metamethods).
+The value at index must be a table.
+
+
+
+
+
+
lua_rawgeti+[-0, +1, –] +
int lua_rawgeti (lua_State *L, int index, lua_Integer n);+ +
+Pushes onto the stack the value t[n],
+where t is the table at the given index.
+The access is raw,
+that is, it does not use the __index metavalue.
+
+
+
+Returns the type of the pushed value. + + + + + +
lua_rawgetp+[-0, +1, –] +
int lua_rawgetp (lua_State *L, int index, const void *p);+ +
+Pushes onto the stack the value t[k],
+where t is the table at the given index and
+k is the pointer p represented as a light userdata.
+The access is raw;
+that is, it does not use the __index metavalue.
+
+
+
+Returns the type of the pushed value. + + + + + +
lua_rawlen+[-0, +0, –] +
lua_Unsigned lua_rawlen (lua_State *L, int index);+ +
+Returns the raw "length" of the value at the given index:
+for strings, this is the string length;
+for tables, this is the result of the length operator ('#')
+with no metamethods;
+for userdata, this is the size of the block of memory allocated
+for the userdata.
+For other values, this call returns 0.
+
+
+
+
+
+
lua_rawset+[-2, +0, m] +
void lua_rawset (lua_State *L, int index);+ +
+Similar to lua_settable, but does a raw assignment
+(i.e., without metamethods).
+The value at index must be a table.
+
+
+
+
+
+
lua_rawseti+[-1, +0, m] +
void lua_rawseti (lua_State *L, int index, lua_Integer i);+ +
+Does the equivalent of t[i] = v,
+where t is the table at the given index
+and v is the value on the top of the stack.
+
+
+
+This function pops the value from the stack.
+The assignment is raw,
+that is, it does not use the __newindex metavalue.
+
+
+
+
+
+
lua_rawsetp+[-1, +0, m] +
void lua_rawsetp (lua_State *L, int index, const void *p);+ +
+Does the equivalent of t[p] = v,
+where t is the table at the given index,
+p is encoded as a light userdata,
+and v is the value on the top of the stack.
+
+
+
+This function pops the value from the stack.
+The assignment is raw,
+that is, it does not use the __newindex metavalue.
+
+
+
+
+
+
lua_Readertypedef const char * (*lua_Reader) (lua_State *L, + void *data, + size_t *size);+ +
+The reader function used by lua_load.
+Every time lua_load needs another piece of the chunk,
+it calls the reader,
+passing along its data parameter.
+The reader must return a pointer to a block of memory
+with a new piece of the chunk
+and set size to the block size.
+The block must exist until the reader function is called again.
+To signal the end of the chunk,
+the reader must return NULL or set size to zero.
+The reader function may return pieces of any size greater than zero.
+
+
+
+
+
+
lua_register+[-0, +0, e] +
void lua_register (lua_State *L, const char *name, lua_CFunction f);+ +
+Sets the C function f as the new value of global name.
+It is defined as a macro:
+
+
+ #define lua_register(L,n,f) \ + (lua_pushcfunction(L, f), lua_setglobal(L, n)) ++ + + + +
lua_remove+[-1, +0, –] +
void lua_remove (lua_State *L, int index);+ +
+Removes the element at the given valid index, +shifting down the elements above this index to fill the gap. +This function cannot be called with a pseudo-index, +because a pseudo-index is not an actual stack position. + + + + + +
lua_replace+[-1, +0, –] +
void lua_replace (lua_State *L, int index);+ +
+Moves the top element into the given valid index +without shifting any element +(therefore replacing the value at that given index), +and then pops the top element. + + + + + +
lua_resetthread+[-0, +?, –] +
int lua_resetthread (lua_State *L);+ +
+This function is deprecated;
+it is equivalent to lua_closethread with
+from being NULL.
+
+
+
+
+
+
lua_resume+[-?, +?, –] +
int lua_resume (lua_State *L, lua_State *from, int nargs, + int *nresults);+ +
+Starts and resumes a coroutine in the given thread L.
+
+
+
+To start a coroutine,
+you push the main function plus any arguments
+onto the empty stack of the thread.
+then you call lua_resume,
+with nargs being the number of arguments.
+This call returns when the coroutine suspends or finishes its execution.
+When it returns,
+*nresults is updated and
+the top of the stack contains
+the *nresults values passed to lua_yield
+or returned by the body function.
+lua_resume returns
+LUA_YIELD if the coroutine yields,
+LUA_OK if the coroutine finishes its execution
+without errors,
+or an error code in case of errors (see §4.4.1).
+In case of errors,
+the error object is on the top of the stack.
+
+
+
+To resume a coroutine,
+you remove the *nresults yielded values from its stack,
+push the values to be passed as results from yield,
+and then call lua_resume.
+
+
+
+The parameter from represents the coroutine that is resuming L.
+If there is no such coroutine,
+this parameter can be NULL.
+
+
+
+
+
+
lua_rotate+[-0, +0, –] +
void lua_rotate (lua_State *L, int idx, int n);+ +
+Rotates the stack elements between the valid index idx
+and the top of the stack.
+The elements are rotated n positions in the direction of the top,
+for a positive n,
+or -n positions in the direction of the bottom,
+for a negative n.
+The absolute value of n must not be greater than the size
+of the slice being rotated.
+This function cannot be called with a pseudo-index,
+because a pseudo-index is not an actual stack position.
+
+
+
+
+
+
lua_setallocf+[-0, +0, –] +
void lua_setallocf (lua_State *L, lua_Alloc f, void *ud);+ +
+Changes the allocator function of a given state to f
+with user data ud.
+
+
+
+
+
+
lua_setfield+[-1, +0, e] +
void lua_setfield (lua_State *L, int index, const char *k);+ +
+Does the equivalent to t[k] = v,
+where t is the value at the given index
+and v is the value on the top of the stack.
+
+
+
+This function pops the value from the stack. +As in Lua, this function may trigger a metamethod +for the "newindex" event (see §2.4). + + + + + +
lua_setglobal+[-1, +0, e] +
void lua_setglobal (lua_State *L, const char *name);+ +
+Pops a value from the stack and
+sets it as the new value of global name.
+
+
+
+
+
+
lua_seti+[-1, +0, e] +
void lua_seti (lua_State *L, int index, lua_Integer n);+ +
+Does the equivalent to t[n] = v,
+where t is the value at the given index
+and v is the value on the top of the stack.
+
+
+
+This function pops the value from the stack. +As in Lua, this function may trigger a metamethod +for the "newindex" event (see §2.4). + + + + + +
lua_setiuservalue+[-1, +0, –] +
int lua_setiuservalue (lua_State *L, int index, int n);+ +
+Pops a value from the stack and sets it as
+the new n-th user value associated to the
+full userdata at the given index.
+Returns 0 if the userdata does not have that value.
+
+
+
+
+
+
lua_setmetatable+[-1, +0, –] +
int lua_setmetatable (lua_State *L, int index);+ +
+Pops a table or nil from the stack and +sets that value as the new metatable for the value at the given index. +(nil means no metatable.) + + +
+(For historical reasons, this function returns an int,
+which now is always 1.)
+
+
+
+
+
+
lua_settable+[-2, +0, e] +
void lua_settable (lua_State *L, int index);+ +
+Does the equivalent to t[k] = v,
+where t is the value at the given index,
+v is the value on the top of the stack,
+and k is the value just below the top.
+
+
+
+This function pops both the key and the value from the stack. +As in Lua, this function may trigger a metamethod +for the "newindex" event (see §2.4). + + + + + +
lua_settop+[-?, +?, e] +
void lua_settop (lua_State *L, int index);+ +
+Accepts any index, or 0,
+and sets the stack top to this index.
+If the new top is greater than the old one,
+then the new elements are filled with nil.
+If index is 0, then all stack elements are removed.
+
+
+
+This function can run arbitrary code when removing an index +marked as to-be-closed from the stack. + + + + + +
lua_setwarnf+[-0, +0, –] +
void lua_setwarnf (lua_State *L, lua_WarnFunction f, void *ud);+ +
+Sets the warning function to be used by Lua to emit warnings
+(see lua_WarnFunction).
+The ud parameter sets the value ud passed to
+the warning function.
+
+
+
+
+
+
lua_Statetypedef struct lua_State lua_State;+ +
+An opaque structure that points to a thread and indirectly +(through the thread) to the whole state of a Lua interpreter. +The Lua library is fully reentrant: +it has no global variables. +All information about a state is accessible through this structure. + + +
+A pointer to this structure must be passed as the first argument to
+every function in the library, except to lua_newstate,
+which creates a Lua state from scratch.
+
+
+
+
+
+
lua_status+[-0, +0, –] +
int lua_status (lua_State *L);+ +
+Returns the status of the thread L.
+
+
+
+The status can be LUA_OK for a normal thread,
+an error code if the thread finished the execution
+of a lua_resume with an error,
+or LUA_YIELD if the thread is suspended.
+
+
+
+You can call functions only in threads with status LUA_OK.
+You can resume threads with status LUA_OK
+(to start a new coroutine) or LUA_YIELD
+(to resume a coroutine).
+
+
+
+
+
+
lua_stringtonumber+[-0, +1, –] +
size_t lua_stringtonumber (lua_State *L, const char *s);+ +
+Converts the zero-terminated string s to a number,
+pushes that number into the stack,
+and returns the total size of the string,
+that is, its length plus one.
+The conversion can result in an integer or a float,
+according to the lexical conventions of Lua (see §3.1).
+The string may have leading and trailing whitespaces and a sign.
+If the string is not a valid numeral,
+returns 0 and pushes nothing.
+(Note that the result can be used as a boolean,
+true if the conversion succeeds.)
+
+
+
+
+
+
lua_toboolean+[-0, +0, –] +
int lua_toboolean (lua_State *L, int index);+ +
+Converts the Lua value at the given index to a C boolean
+value (0 or 1).
+Like all tests in Lua,
+lua_toboolean returns true for any Lua value
+different from false and nil;
+otherwise it returns false.
+(If you want to accept only actual boolean values,
+use lua_isboolean to test the value's type.)
+
+
+
+
+
+
lua_tocfunction+[-0, +0, –] +
lua_CFunction lua_tocfunction (lua_State *L, int index);+ +
+Converts a value at the given index to a C function.
+That value must be a C function;
+otherwise, returns NULL.
+
+
+
+
+
+
lua_toclose+[-0, +0, v] +
void lua_toclose (lua_State *L, int index);+ +
+Marks the given index in the stack as a
+to-be-closed slot (see §3.3.8).
+Like a to-be-closed variable in Lua,
+the value at that slot in the stack will be closed
+when it goes out of scope.
+Here, in the context of a C function,
+to go out of scope means that the running function returns to Lua,
+or there is an error,
+or the slot is removed from the stack through
+lua_settop or lua_pop,
+or there is a call to lua_closeslot.
+A slot marked as to-be-closed should not be removed from the stack
+by any other function in the API except lua_settop or lua_pop,
+unless previously deactivated by lua_closeslot.
+
+
+
+This function raises an error if the value at the given slot
+neither has a __close metamethod nor is a false value.
+
+
+
+This function should not be called for an index +that is equal to or below an active to-be-closed slot. + + +
+Note that, both in case of errors and of a regular return,
+by the time the __close metamethod runs,
+the C stack was already unwound,
+so that any automatic C variable declared in the calling function
+(e.g., a buffer) will be out of scope.
+
+
+
+
+
+
lua_tointeger+[-0, +0, –] +
lua_Integer lua_tointeger (lua_State *L, int index);+ +
+Equivalent to lua_tointegerx with isnum equal to NULL.
+
+
+
+
+
+
lua_tointegerx+[-0, +0, –] +
lua_Integer lua_tointegerx (lua_State *L, int index, int *isnum);+ +
+Converts the Lua value at the given index
+to the signed integral type lua_Integer.
+The Lua value must be an integer,
+or a number or string convertible to an integer (see §3.4.3);
+otherwise, lua_tointegerx returns 0.
+
+
+
+If isnum is not NULL,
+its referent is assigned a boolean value that
+indicates whether the operation succeeded.
+
+
+
+
+
+
lua_tolstring+[-0, +0, m] +
const char *lua_tolstring (lua_State *L, int index, size_t *len);+ +
+Converts the Lua value at the given index to a C string.
+If len is not NULL,
+it sets *len with the string length.
+The Lua value must be a string or a number;
+otherwise, the function returns NULL.
+If the value is a number,
+then lua_tolstring also
+changes the actual value in the stack to a string.
+(This change confuses lua_next
+when lua_tolstring is applied to keys during a table traversal.)
+
+
+
+lua_tolstring returns a pointer
+to a string inside the Lua state (see §4.1.3).
+This string always has a zero ('\0')
+after its last character (as in C),
+but can contain other zeros in its body.
+
+
+
+This function can raise memory errors only +when converting a number to a string +(as then it may create a new string). + + + + + +
lua_tonumber+[-0, +0, –] +
lua_Number lua_tonumber (lua_State *L, int index);+ +
+Equivalent to lua_tonumberx with isnum equal to NULL.
+
+
+
+
+
+
lua_tonumberx+[-0, +0, –] +
lua_Number lua_tonumberx (lua_State *L, int index, int *isnum);+ +
+Converts the Lua value at the given index
+to the C type lua_Number (see lua_Number).
+The Lua value must be a number or a string convertible to a number
+(see §3.4.3);
+otherwise, lua_tonumberx returns 0.
+
+
+
+If isnum is not NULL,
+its referent is assigned a boolean value that
+indicates whether the operation succeeded.
+
+
+
+
+
+
lua_topointer+[-0, +0, –] +
const void *lua_topointer (lua_State *L, int index);+ +
+Converts the value at the given index to a generic
+C pointer (void*).
+The value can be a userdata, a table, a thread, a string, or a function;
+otherwise, lua_topointer returns NULL.
+Different objects will give different pointers.
+There is no way to convert the pointer back to its original value.
+
+
+
+Typically this function is used only for hashing and debug information. + + + + + +
lua_tostring+[-0, +0, m] +
const char *lua_tostring (lua_State *L, int index);+ +
+Equivalent to lua_tolstring with len equal to NULL.
+
+
+
+
+
+
lua_tothread+[-0, +0, –] +
lua_State *lua_tothread (lua_State *L, int index);+ +
+Converts the value at the given index to a Lua thread
+(represented as lua_State*).
+This value must be a thread;
+otherwise, the function returns NULL.
+
+
+
+
+
+
lua_touserdata+[-0, +0, –] +
void *lua_touserdata (lua_State *L, int index);+ +
+If the value at the given index is a full userdata,
+returns its memory-block address.
+If the value is a light userdata,
+returns its value (a pointer).
+Otherwise, returns NULL.
+
+
+
+
+
+
lua_type+[-0, +0, –] +
int lua_type (lua_State *L, int index);+ +
+Returns the type of the value in the given valid index,
+or LUA_TNONE for a non-valid but acceptable index.
+The types returned by lua_type are coded by the following constants
+defined in lua.h:
+LUA_TNIL,
+LUA_TNUMBER,
+LUA_TBOOLEAN,
+LUA_TSTRING,
+LUA_TTABLE,
+LUA_TFUNCTION,
+LUA_TUSERDATA,
+LUA_TTHREAD,
+and
+LUA_TLIGHTUSERDATA.
+
+
+
+
+
+
lua_typename+[-0, +0, –] +
const char *lua_typename (lua_State *L, int tp);+ +
+Returns the name of the type encoded by the value tp,
+which must be one the values returned by lua_type.
+
+
+
+
+
+
lua_Unsignedtypedef ... lua_Unsigned;+ +
+The unsigned version of lua_Integer.
+
+
+
+
+
+
lua_upvalueindex+[-0, +0, –] +
int lua_upvalueindex (int i);+ +
+Returns the pseudo-index that represents the i-th upvalue of
+the running function (see §4.2).
+i must be in the range [1,256].
+
+
+
+
+
+
lua_version+[-0, +0, –] +
lua_Number lua_version (lua_State *L);+ +
+Returns the version number of this core. + + + + + +
lua_WarnFunctiontypedef void (*lua_WarnFunction) (void *ud, const char *msg, int tocont);+ +
+The type of warning functions, called by Lua to emit warnings.
+The first parameter is an opaque pointer
+set by lua_setwarnf.
+The second parameter is the warning message.
+The third parameter is a boolean that
+indicates whether the message is
+to be continued by the message in the next call.
+
+
+
+See warn for more details about warnings.
+
+
+
+
+
+
lua_warning+[-0, +0, –] +
void lua_warning (lua_State *L, const char *msg, int tocont);+ +
+Emits a warning with the given message.
+A message in a call with tocont true should be
+continued in another call to this function.
+
+
+
+See warn for more details about warnings.
+
+
+
+
+
+
lua_Writertypedef int (*lua_Writer) (lua_State *L, + const void* p, + size_t sz, + void* ud);+ +
+The type of the writer function used by lua_dump.
+Every time lua_dump produces another piece of chunk,
+it calls the writer,
+passing along the buffer to be written (p),
+its size (sz),
+and the ud parameter supplied to lua_dump.
+
+
+
+The writer returns an error code:
+0 means no errors;
+any other value means an error and stops lua_dump from
+calling the writer again.
+
+
+
+
+
+
lua_xmove+[-?, +?, –] +
void lua_xmove (lua_State *from, lua_State *to, int n);+ +
+Exchange values between different threads of the same state. + + +
+This function pops n values from the stack from,
+and pushes them onto the stack to.
+
+
+
+
+
+
lua_yield+[-?, +?, v] +
int lua_yield (lua_State *L, int nresults);+ +
+This function is equivalent to lua_yieldk,
+but it has no continuation (see §4.5).
+Therefore, when the thread resumes,
+it continues the function that called
+the function calling lua_yield.
+To avoid surprises,
+this function should be called only in a tail call.
+
+
+
+
+
+
lua_yieldk+[-?, +?, v] +
int lua_yieldk (lua_State *L, + int nresults, + lua_KContext ctx, + lua_KFunction k);+ +
+Yields a coroutine (thread). + + +
+When a C function calls lua_yieldk,
+the running coroutine suspends its execution,
+and the call to lua_resume that started this coroutine returns.
+The parameter nresults is the number of values from the stack
+that will be passed as results to lua_resume.
+
+
+
+When the coroutine is resumed again,
+Lua calls the given continuation function k to continue
+the execution of the C function that yielded (see §4.5).
+This continuation function receives the same stack
+from the previous function,
+with the n results removed and
+replaced by the arguments passed to lua_resume.
+Moreover,
+the continuation function receives the value ctx
+that was passed to lua_yieldk.
+
+
+
+Usually, this function does not return;
+when the coroutine eventually resumes,
+it continues executing the continuation function.
+However, there is one special case,
+which is when this function is called
+from inside a line or a count hook (see §4.7).
+In that case, lua_yieldk should be called with no continuation
+(probably in the form of lua_yield) and no results,
+and the hook should return immediately after the call.
+Lua will yield and,
+when the coroutine resumes again,
+it will continue the normal execution
+of the (Lua) function that triggered the hook.
+
+
+
+This function can raise an error if it is called from a thread +with a pending C call with no continuation function +(what is called a C-call boundary), +or it is called from a thread that is not running inside a resume +(typically the main thread). + + + + + + + +
+Lua has no built-in debugging facilities. +Instead, it offers a special interface +by means of functions and hooks. +This interface allows the construction of different +kinds of debuggers, profilers, and other tools +that need "inside information" from the interpreter. + + + +
lua_Debugtypedef struct lua_Debug {
+ int event;
+ const char *name; /* (n) */
+ const char *namewhat; /* (n) */
+ const char *what; /* (S) */
+ const char *source; /* (S) */
+ size_t srclen; /* (S) */
+ int currentline; /* (l) */
+ int linedefined; /* (S) */
+ int lastlinedefined; /* (S) */
+ unsigned char nups; /* (u) number of upvalues */
+ unsigned char nparams; /* (u) number of parameters */
+ char isvararg; /* (u) */
+ char istailcall; /* (t) */
+ unsigned short ftransfer; /* (r) index of first value transferred */
+ unsigned short ntransfer; /* (r) number of transferred values */
+ char short_src[LUA_IDSIZE]; /* (S) */
+ /* private part */
+ other fields
+} lua_Debug;
+
+
+A structure used to carry different pieces of
+information about a function or an activation record.
+lua_getstack fills only the private part
+of this structure, for later use.
+To fill the other fields of lua_Debug with useful information,
+you must call lua_getinfo with an appropriate parameter.
+(Specifically, to get a field,
+you must add the letter between parentheses in the field's comment
+to the parameter what of lua_getinfo.)
+
+
+
+The fields of lua_Debug have the following meaning:
+
+
source:
+the source of the chunk that created the function.
+If source starts with a '@',
+it means that the function was defined in a file where
+the file name follows the '@'.
+If source starts with a '=',
+the remainder of its contents describes the source in a user-dependent manner.
+Otherwise,
+the function was defined in a string where
+source is that string.
+srclen:
+The length of the string source.
+short_src:
+a "printable" version of source, to be used in error messages.
+linedefined:
+the line number where the definition of the function starts.
+lastlinedefined:
+the line number where the definition of the function ends.
+what:
+the string "Lua" if the function is a Lua function,
+"C" if it is a C function,
+"main" if it is the main part of a chunk.
+currentline:
+the current line where the given function is executing.
+When no line information is available,
+currentline is set to -1.
+name:
+a reasonable name for the given function.
+Because functions in Lua are first-class values,
+they do not have a fixed name:
+some functions can be the value of multiple global variables,
+while others can be stored only in a table field.
+The lua_getinfo function checks how the function was
+called to find a suitable name.
+If it cannot find a name,
+then name is set to NULL.
+namewhat:
+explains the name field.
+The value of namewhat can be
+"global", "local", "method",
+"field", "upvalue", or "" (the empty string),
+according to how the function was called.
+(Lua uses the empty string when no other option seems to apply.)
+istailcall:
+true if this function invocation was called by a tail call.
+In this case, the caller of this level is not in the stack.
+nups:
+the number of upvalues of the function.
+nparams:
+the number of parameters of the function
+(always 0 for C functions).
+isvararg:
+true if the function is a variadic function
+(always true for C functions).
+ftransfer:
+the index in the stack of the first value being "transferred",
+that is, parameters in a call or return values in a return.
+(The other values are in consecutive indices.)
+Using this index, you can access and modify these values
+through lua_getlocal and lua_setlocal.
+This field is only meaningful during a
+call hook, denoting the first parameter,
+or a return hook, denoting the first value being returned.
+(For call hooks, this value is always 1.)
+ntransfer:
+The number of values being transferred (see previous item).
+(For calls of Lua functions,
+this value is always equal to nparams.)
+lua_gethook+[-0, +0, –] +
lua_Hook lua_gethook (lua_State *L);+ +
+Returns the current hook function. + + + + + +
lua_gethookcount+[-0, +0, –] +
int lua_gethookcount (lua_State *L);+ +
+Returns the current hook count. + + + + + +
lua_gethookmask+[-0, +0, –] +
int lua_gethookmask (lua_State *L);+ +
+Returns the current hook mask. + + + + + +
lua_getinfo+[-(0|1), +(0|1|2), m] +
int lua_getinfo (lua_State *L, const char *what, lua_Debug *ar);+ +
+Gets information about a specific function or function invocation. + + +
+To get information about a function invocation,
+the parameter ar must be a valid activation record that was
+filled by a previous call to lua_getstack or
+given as argument to a hook (see lua_Hook).
+
+
+
+To get information about a function, you push it onto the stack
+and start the what string with the character '>'.
+(In that case,
+lua_getinfo pops the function from the top of the stack.)
+For instance, to know in which line a function f was defined,
+you can write the following code:
+
+
+ lua_Debug ar;
+ lua_getglobal(L, "f"); /* get global 'f' */
+ lua_getinfo(L, ">S", &ar);
+ printf("%d\n", ar.linedefined);
+
+
+
+Each character in the string what
+selects some fields of the structure ar to be filled or
+a value to be pushed on the stack.
+(These characters are also documented in the declaration of
+the structure lua_Debug,
+between parentheses in the comments following each field.)
+
+
f':
+pushes onto the stack the function that is
+running at the given level;
+l': fills in the field currentline;
+n': fills in the fields name and namewhat;
+r': fills in the fields ftransfer and ntransfer;
+S':
+fills in the fields source, short_src,
+linedefined, lastlinedefined, and what;
+t': fills in the field istailcall;
+u': fills in the fields
+nups, nparams, and isvararg;
+L':
+pushes onto the stack a table whose indices are
+the lines on the function with some associated code,
+that is, the lines where you can put a break point.
+(Lines with no code include empty lines and comments.)
+If this option is given together with option 'f',
+its table is pushed after the function.
+This is the only option that can raise a memory error.
+
+This function returns 0 to signal an invalid option in what;
+even then the valid options are handled correctly.
+
+
+
+
+
+
lua_getlocal+[-0, +(0|1), –] +
const char *lua_getlocal (lua_State *L, const lua_Debug *ar, int n);+ +
+Gets information about a local variable or a temporary value +of a given activation record or a given function. + + +
+In the first case,
+the parameter ar must be a valid activation record that was
+filled by a previous call to lua_getstack or
+given as argument to a hook (see lua_Hook).
+The index n selects which local variable to inspect;
+see debug.getlocal for details about variable indices
+and names.
+
+
+
+lua_getlocal pushes the variable's value onto the stack
+and returns its name.
+
+
+
+In the second case, ar must be NULL and the function
+to be inspected must be on the top of the stack.
+In this case, only parameters of Lua functions are visible
+(as there is no information about what variables are active)
+and no values are pushed onto the stack.
+
+
+
+Returns NULL (and pushes nothing)
+when the index is greater than
+the number of active local variables.
+
+
+
+
+
+
lua_getstack+[-0, +0, –] +
int lua_getstack (lua_State *L, int level, lua_Debug *ar);+ +
+Gets information about the interpreter runtime stack. + + +
+This function fills parts of a lua_Debug structure with
+an identification of the activation record
+of the function executing at a given level.
+Level 0 is the current running function,
+whereas level n+1 is the function that has called level n
+(except for tail calls, which do not count in the stack).
+When called with a level greater than the stack depth,
+lua_getstack returns 0;
+otherwise it returns 1.
+
+
+
+
+
+
lua_getupvalue+[-0, +(0|1), –] +
const char *lua_getupvalue (lua_State *L, int funcindex, int n);+ +
+Gets information about the n-th upvalue
+of the closure at index funcindex.
+It pushes the upvalue's value onto the stack
+and returns its name.
+Returns NULL (and pushes nothing)
+when the index n is greater than the number of upvalues.
+
+
+
+See debug.getupvalue for more information about upvalues.
+
+
+
+
+
+
lua_Hooktypedef void (*lua_Hook) (lua_State *L, lua_Debug *ar);+ +
+Type for debugging hook functions. + + +
+Whenever a hook is called, its ar argument has its field
+event set to the specific event that triggered the hook.
+Lua identifies these events with the following constants:
+LUA_HOOKCALL, LUA_HOOKRET,
+LUA_HOOKTAILCALL, LUA_HOOKLINE,
+and LUA_HOOKCOUNT.
+Moreover, for line events, the field currentline is also set.
+To get the value of any other field in ar,
+the hook must call lua_getinfo.
+
+
+
+For call events, event can be LUA_HOOKCALL,
+the normal value, or LUA_HOOKTAILCALL, for a tail call;
+in this case, there will be no corresponding return event.
+
+
+
+While Lua is running a hook, it disables other calls to hooks. +Therefore, if a hook calls back Lua to execute a function or a chunk, +this execution occurs without any calls to hooks. + + +
+Hook functions cannot have continuations,
+that is, they cannot call lua_yieldk,
+lua_pcallk, or lua_callk with a non-null k.
+
+
+
+Hook functions can yield under the following conditions:
+Only count and line events can yield;
+to yield, a hook function must finish its execution
+calling lua_yield with nresults equal to zero
+(that is, with no values).
+
+
+
+
+
+
lua_sethook+[-0, +0, –] +
void lua_sethook (lua_State *L, lua_Hook f, int mask, int count);+ +
+Sets the debugging hook function. + + +
+Argument f is the hook function.
+mask specifies on which events the hook will be called:
+it is formed by a bitwise OR of the constants
+LUA_MASKCALL,
+LUA_MASKRET,
+LUA_MASKLINE,
+and LUA_MASKCOUNT.
+The count argument is only meaningful when the mask
+includes LUA_MASKCOUNT.
+For each event, the hook is called as explained below:
+
+
count instructions.
+This event only happens while Lua is executing a Lua function.
+
+Hooks are disabled by setting mask to zero.
+
+
+
+
+
+
lua_setlocal+[-(0|1), +0, –] +
const char *lua_setlocal (lua_State *L, const lua_Debug *ar, int n);+ +
+Sets the value of a local variable of a given activation record. +It assigns the value on the top of the stack +to the variable and returns its name. +It also pops the value from the stack. + + +
+Returns NULL (and pops nothing)
+when the index is greater than
+the number of active local variables.
+
+
+
+Parameters ar and n are as in the function lua_getlocal.
+
+
+
+
+
+
lua_setupvalue+[-(0|1), +0, –] +
const char *lua_setupvalue (lua_State *L, int funcindex, int n);+ +
+Sets the value of a closure's upvalue. +It assigns the value on the top of the stack +to the upvalue and returns its name. +It also pops the value from the stack. + + +
+Returns NULL (and pops nothing)
+when the index n is greater than the number of upvalues.
+
+
+
+Parameters funcindex and n are as in
+the function lua_getupvalue.
+
+
+
+
+
+
lua_upvalueid+[-0, +0, –] +
void *lua_upvalueid (lua_State *L, int funcindex, int n);+ +
+Returns a unique identifier for the upvalue numbered n
+from the closure at index funcindex.
+
+
+
+These unique identifiers allow a program to check whether different +closures share upvalues. +Lua closures that share an upvalue +(that is, that access a same external local variable) +will return identical ids for those upvalue indices. + + +
+Parameters funcindex and n are as in
+the function lua_getupvalue,
+but n cannot be greater than the number of upvalues.
+
+
+
+
+
+
lua_upvaluejoin+[-0, +0, –] +
void lua_upvaluejoin (lua_State *L, int funcindex1, int n1, + int funcindex2, int n2);+ +
+Make the n1-th upvalue of the Lua closure at index funcindex1
+refer to the n2-th upvalue of the Lua closure at index funcindex2.
+
+
+
+
+
+
+
+
+ +The auxiliary library provides several convenient functions +to interface C with Lua. +While the basic API provides the primitive functions for all +interactions between C and Lua, +the auxiliary library provides higher-level functions for some +common tasks. + + +
+All functions and types from the auxiliary library
+are defined in header file lauxlib.h and
+have a prefix luaL_.
+
+
+
+All functions in the auxiliary library are built on +top of the basic API, +and so they provide nothing that cannot be done with that API. +Nevertheless, the use of the auxiliary library ensures +more consistency to your code. + + +
+Several functions in the auxiliary library use internally some +extra stack slots. +When a function in the auxiliary library uses less than five slots, +it does not check the stack size; +it simply assumes that there are enough slots. + + +
+Several functions in the auxiliary library are used to
+check C function arguments.
+Because the error message is formatted for arguments
+(e.g., "bad argument #1"),
+you should not use these functions for other stack values.
+
+
+
+Functions called luaL_check*
+always raise an error if the check is not satisfied.
+
+
+
+
+
+
+Here we list all functions and types from the auxiliary library +in alphabetical order. + + + +
luaL_addchar+[-?, +?, m] +
void luaL_addchar (luaL_Buffer *B, char c);+ +
+Adds the byte c to the buffer B
+(see luaL_Buffer).
+
+
+
+
+
+
luaL_addgsub+[-?, +?, m] +
const void luaL_addgsub (luaL_Buffer *B, const char *s, + const char *p, const char *r);+ +
+Adds a copy of the string s to the buffer B (see luaL_Buffer),
+replacing any occurrence of the string p
+with the string r.
+
+
+
+
+
+
luaL_addlstring+[-?, +?, m] +
void luaL_addlstring (luaL_Buffer *B, const char *s, size_t l);+ +
+Adds the string pointed to by s with length l to
+the buffer B
+(see luaL_Buffer).
+The string can contain embedded zeros.
+
+
+
+
+
+
luaL_addsize+[-?, +?, –] +
void luaL_addsize (luaL_Buffer *B, size_t n);+ +
+Adds to the buffer B
+a string of length n previously copied to the
+buffer area (see luaL_prepbuffer).
+
+
+
+
+
+
luaL_addstring+[-?, +?, m] +
void luaL_addstring (luaL_Buffer *B, const char *s);+ +
+Adds the zero-terminated string pointed to by s
+to the buffer B
+(see luaL_Buffer).
+
+
+
+
+
+
luaL_addvalue+[-?, +?, m] +
void luaL_addvalue (luaL_Buffer *B);+ +
+Adds the value on the top of the stack
+to the buffer B
+(see luaL_Buffer).
+Pops the value.
+
+
+
+This is the only function on string buffers that can (and must) +be called with an extra element on the stack, +which is the value to be added to the buffer. + + + + + +
luaL_argcheck+[-0, +0, v] +
void luaL_argcheck (lua_State *L, + int cond, + int arg, + const char *extramsg);+ +
+Checks whether cond is true.
+If it is not, raises an error with a standard message (see luaL_argerror).
+
+
+
+
+
+
luaL_argerror+[-0, +0, v] +
int luaL_argerror (lua_State *L, int arg, const char *extramsg);+ +
+Raises an error reporting a problem with argument arg
+of the C function that called it,
+using a standard message
+that includes extramsg as a comment:
+
+
+ bad argument #arg to 'funcname' (extramsg) +
+This function never returns. + + + + + +
luaL_argexpected+[-0, +0, v] +
void luaL_argexpected (lua_State *L, + int cond, + int arg, + const char *tname);+ +
+Checks whether cond is true.
+If it is not, raises an error about the type of the argument arg
+with a standard message (see luaL_typeerror).
+
+
+
+
+
+
luaL_Buffertypedef struct luaL_Buffer luaL_Buffer;+ +
+Type for a string buffer. + + +
+A string buffer allows C code to build Lua strings piecemeal. +Its pattern of use is as follows: + +
b of type luaL_Buffer.luaL_buffinit(L, &b).luaL_add* functions.
+luaL_pushresult(&b).
+This call leaves the final string on the top of the stack.
++If you know beforehand the maximum size of the resulting string, +you can use the buffer like this: + +
b of type luaL_Buffer.sz with a call luaL_buffinitsize(L, &b, sz).luaL_pushresultsize(&b, sz),
+where sz is the total size of the resulting string
+copied into that space (which may be less than or
+equal to the preallocated size).
+
+During its normal operation,
+a string buffer uses a variable number of stack slots.
+So, while using a buffer, you cannot assume that you know where
+the top of the stack is.
+You can use the stack between successive calls to buffer operations
+as long as that use is balanced;
+that is,
+when you call a buffer operation,
+the stack is at the same level
+it was immediately after the previous buffer operation.
+(The only exception to this rule is luaL_addvalue.)
+After calling luaL_pushresult,
+the stack is back to its level when the buffer was initialized,
+plus the final string on its top.
+
+
+
+
+
+
luaL_buffaddr+[-0, +0, –] +
char *luaL_buffaddr (luaL_Buffer *B);+ +
+Returns the address of the current content of buffer B
+(see luaL_Buffer).
+Note that any addition to the buffer may invalidate this address.
+
+
+
+
+
+
luaL_buffinit+[-0, +?, –] +
void luaL_buffinit (lua_State *L, luaL_Buffer *B);+ +
+Initializes a buffer B
+(see luaL_Buffer).
+This function does not allocate any space;
+the buffer must be declared as a variable.
+
+
+
+
+
+
luaL_bufflen+[-0, +0, –] +
size_t luaL_bufflen (luaL_Buffer *B);+ +
+Returns the length of the current content of buffer B
+(see luaL_Buffer).
+
+
+
+
+
+
luaL_buffinitsize+[-?, +?, m] +
char *luaL_buffinitsize (lua_State *L, luaL_Buffer *B, size_t sz);+ +
+Equivalent to the sequence
+luaL_buffinit, luaL_prepbuffsize.
+
+
+
+
+
+
luaL_buffsub+[-?, +?, –] +
void luaL_buffsub (luaL_Buffer *B, int n);+ +
+Removes n bytes from the buffer B
+(see luaL_Buffer).
+The buffer must have at least that many bytes.
+
+
+
+
+
+
luaL_callmeta+[-0, +(0|1), e] +
int luaL_callmeta (lua_State *L, int obj, const char *e);+ +
+Calls a metamethod. + + +
+If the object at index obj has a metatable and this
+metatable has a field e,
+this function calls this field passing the object as its only argument.
+In this case this function returns true and pushes onto the
+stack the value returned by the call.
+If there is no metatable or no metamethod,
+this function returns false without pushing any value on the stack.
+
+
+
+
+
+
luaL_checkany+[-0, +0, v] +
void luaL_checkany (lua_State *L, int arg);+ +
+Checks whether the function has an argument
+of any type (including nil) at position arg.
+
+
+
+
+
+
luaL_checkinteger+[-0, +0, v] +
lua_Integer luaL_checkinteger (lua_State *L, int arg);+ +
+Checks whether the function argument arg is an integer
+(or can be converted to an integer)
+and returns this integer.
+
+
+
+
+
+
luaL_checklstring+[-0, +0, v] +
const char *luaL_checklstring (lua_State *L, int arg, size_t *l);+ +
+Checks whether the function argument arg is a string
+and returns this string;
+if l is not NULL fills its referent
+with the string's length.
+
+
+
+This function uses lua_tolstring to get its result,
+so all conversions and caveats of that function apply here.
+
+
+
+
+
+
luaL_checknumber+[-0, +0, v] +
lua_Number luaL_checknumber (lua_State *L, int arg);+ +
+Checks whether the function argument arg is a number
+and returns this number converted to a lua_Number.
+
+
+
+
+
+
luaL_checkoption+[-0, +0, v] +
int luaL_checkoption (lua_State *L, + int arg, + const char *def, + const char *const lst[]);+ +
+Checks whether the function argument arg is a string and
+searches for this string in the array lst
+(which must be NULL-terminated).
+Returns the index in the array where the string was found.
+Raises an error if the argument is not a string or
+if the string cannot be found.
+
+
+
+If def is not NULL,
+the function uses def as a default value when
+there is no argument arg or when this argument is nil.
+
+
+
+This is a useful function for mapping strings to C enums. +(The usual convention in Lua libraries is +to use strings instead of numbers to select options.) + + + + + +
luaL_checkstack+[-0, +0, v] +
void luaL_checkstack (lua_State *L, int sz, const char *msg);+ +
+Grows the stack size to top + sz elements,
+raising an error if the stack cannot grow to that size.
+msg is an additional text to go into the error message
+(or NULL for no additional text).
+
+
+
+
+
+
luaL_checkstring+[-0, +0, v] +
const char *luaL_checkstring (lua_State *L, int arg);+ +
+Checks whether the function argument arg is a string
+and returns this string.
+
+
+
+This function uses lua_tolstring to get its result,
+so all conversions and caveats of that function apply here.
+
+
+
+
+
+
luaL_checktype+[-0, +0, v] +
void luaL_checktype (lua_State *L, int arg, int t);+ +
+Checks whether the function argument arg has type t.
+See lua_type for the encoding of types for t.
+
+
+
+
+
+
luaL_checkudata+[-0, +0, v] +
void *luaL_checkudata (lua_State *L, int arg, const char *tname);+ +
+Checks whether the function argument arg is a userdata
+of the type tname (see luaL_newmetatable) and
+returns the userdata's memory-block address (see lua_touserdata).
+
+
+
+
+
+
luaL_checkversion+[-0, +0, v] +
void luaL_checkversion (lua_State *L);+ +
+Checks whether the code making the call and the Lua library being called +are using the same version of Lua and the same numeric types. + + + + + +
luaL_dofile+[-0, +?, m] +
int luaL_dofile (lua_State *L, const char *filename);+ +
+Loads and runs the given file. +It is defined as the following macro: + +
+ (luaL_loadfile(L, filename) || lua_pcall(L, 0, LUA_MULTRET, 0)) +
+It returns 0 (LUA_OK) if there are no errors,
+or 1 in case of errors.
+
+
+
+
+
+
luaL_dostring+[-0, +?, –] +
int luaL_dostring (lua_State *L, const char *str);+ +
+Loads and runs the given string. +It is defined as the following macro: + +
+ (luaL_loadstring(L, str) || lua_pcall(L, 0, LUA_MULTRET, 0)) +
+It returns 0 (LUA_OK) if there are no errors,
+or 1 in case of errors.
+
+
+
+
+
+
luaL_error+[-0, +0, v] +
int luaL_error (lua_State *L, const char *fmt, ...);+ +
+Raises an error.
+The error message format is given by fmt
+plus any extra arguments,
+following the same rules of lua_pushfstring.
+It also adds at the beginning of the message the file name and
+the line number where the error occurred,
+if this information is available.
+
+
+
+This function never returns,
+but it is an idiom to use it in C functions
+as return luaL_error(args).
+
+
+
+
+
+
luaL_execresult+[-0, +3, m] +
int luaL_execresult (lua_State *L, int stat);+ +
+This function produces the return values for
+process-related functions in the standard library
+(os.execute and io.close).
+
+
+
+
+
+
luaL_fileresult+[-0, +(1|3), m] +
int luaL_fileresult (lua_State *L, int stat, const char *fname);+ +
+This function produces the return values for
+file-related functions in the standard library
+(io.open, os.rename, file:seek, etc.).
+
+
+
+
+
+
luaL_getmetafield+[-0, +(0|1), m] +
int luaL_getmetafield (lua_State *L, int obj, const char *e);+ +
+Pushes onto the stack the field e from the metatable
+of the object at index obj and returns the type of the pushed value.
+If the object does not have a metatable,
+or if the metatable does not have this field,
+pushes nothing and returns LUA_TNIL.
+
+
+
+
+
+
luaL_getmetatable+[-0, +1, m] +
int luaL_getmetatable (lua_State *L, const char *tname);+ +
+Pushes onto the stack the metatable associated with the name tname
+in the registry (see luaL_newmetatable),
+or nil if there is no metatable associated with that name.
+Returns the type of the pushed value.
+
+
+
+
+
+
luaL_getsubtable+[-0, +1, e] +
int luaL_getsubtable (lua_State *L, int idx, const char *fname);+ +
+Ensures that the value t[fname],
+where t is the value at index idx,
+is a table,
+and pushes that table onto the stack.
+Returns true if it finds a previous table there
+and false if it creates a new table.
+
+
+
+
+
+
luaL_gsub+[-0, +1, m] +
const char *luaL_gsub (lua_State *L, + const char *s, + const char *p, + const char *r);+ +
+Creates a copy of string s,
+replacing any occurrence of the string p
+with the string r.
+Pushes the resulting string on the stack and returns it.
+
+
+
+
+
+
luaL_len+[-0, +0, e] +
lua_Integer luaL_len (lua_State *L, int index);+ +
+Returns the "length" of the value at the given index
+as a number;
+it is equivalent to the '#' operator in Lua (see §3.4.7).
+Raises an error if the result of the operation is not an integer.
+(This case can only happen through metamethods.)
+
+
+
+
+
+
luaL_loadbuffer+[-0, +1, –] +
int luaL_loadbuffer (lua_State *L, + const char *buff, + size_t sz, + const char *name);+ +
+Equivalent to luaL_loadbufferx with mode equal to NULL.
+
+
+
+
+
+
luaL_loadbufferx+[-0, +1, –] +
int luaL_loadbufferx (lua_State *L, + const char *buff, + size_t sz, + const char *name, + const char *mode);+ +
+Loads a buffer as a Lua chunk.
+This function uses lua_load to load the chunk in the
+buffer pointed to by buff with size sz.
+
+
+
+This function returns the same results as lua_load.
+name is the chunk name,
+used for debug information and error messages.
+The string mode works as in the function lua_load.
+
+
+
+
+
+
luaL_loadfile+[-0, +1, m] +
int luaL_loadfile (lua_State *L, const char *filename);+ +
+Equivalent to luaL_loadfilex with mode equal to NULL.
+
+
+
+
+
+
luaL_loadfilex+[-0, +1, m] +
int luaL_loadfilex (lua_State *L, const char *filename, + const char *mode);+ +
+Loads a file as a Lua chunk.
+This function uses lua_load to load the chunk in the file
+named filename.
+If filename is NULL,
+then it loads from the standard input.
+The first line in the file is ignored if it starts with a #.
+
+
+
+The string mode works as in the function lua_load.
+
+
+
+This function returns the same results as lua_load
+or LUA_ERRFILE for file-related errors.
+
+
+
+As lua_load, this function only loads the chunk;
+it does not run it.
+
+
+
+
+
+
luaL_loadstring+[-0, +1, –] +
int luaL_loadstring (lua_State *L, const char *s);+ +
+Loads a string as a Lua chunk.
+This function uses lua_load to load the chunk in
+the zero-terminated string s.
+
+
+
+This function returns the same results as lua_load.
+
+
+
+Also as lua_load, this function only loads the chunk;
+it does not run it.
+
+
+
+
+
+
luaL_newlib+[-0, +1, m] +
void luaL_newlib (lua_State *L, const luaL_Reg l[]);+ +
+Creates a new table and registers there
+the functions in the list l.
+
+
+
+It is implemented as the following macro: + +
+ (luaL_newlibtable(L,l), luaL_setfuncs(L,l,0)) +
+The array l must be the actual array,
+not a pointer to it.
+
+
+
+
+
+
luaL_newlibtable+[-0, +1, m] +
void luaL_newlibtable (lua_State *L, const luaL_Reg l[]);+ +
+Creates a new table with a size optimized
+to store all entries in the array l
+(but does not actually store them).
+It is intended to be used in conjunction with luaL_setfuncs
+(see luaL_newlib).
+
+
+
+It is implemented as a macro.
+The array l must be the actual array,
+not a pointer to it.
+
+
+
+
+
+
luaL_newmetatable+[-0, +1, m] +
int luaL_newmetatable (lua_State *L, const char *tname);+ +
+If the registry already has the key tname,
+returns 0.
+Otherwise,
+creates a new table to be used as a metatable for userdata,
+adds to this new table the pair __name = tname,
+adds to the registry the pair [tname] = new table,
+and returns 1.
+
+
+
+In both cases,
+the function pushes onto the stack the final value associated
+with tname in the registry.
+
+
+
+
+
+
luaL_newstate+[-0, +0, –] +
lua_State *luaL_newstate (void);+ +
+Creates a new Lua state.
+It calls lua_newstate with an
+allocator based on the ISO C allocation functions
+and then sets a warning function and a panic function (see §4.4)
+that print messages to the standard error output.
+
+
+
+Returns the new state,
+or NULL if there is a memory allocation error.
+
+
+
+
+
+
luaL_openlibs+[-0, +0, e] +
void luaL_openlibs (lua_State *L);+ +
+Opens all standard Lua libraries into the given state. + + + + + +
luaL_opt+[-0, +0, –] +
T luaL_opt (L, func, arg, dflt);+ +
+This macro is defined as follows: + +
+ (lua_isnoneornil(L,(arg)) ? (dflt) : func(L,(arg))) +
+In words, if the argument arg is nil or absent,
+the macro results in the default dflt.
+Otherwise, it results in the result of calling func
+with the state L and the argument index arg as
+arguments.
+Note that it evaluates the expression dflt only if needed.
+
+
+
+
+
+
luaL_optinteger+[-0, +0, v] +
lua_Integer luaL_optinteger (lua_State *L, + int arg, + lua_Integer d);+ +
+If the function argument arg is an integer
+(or it is convertible to an integer),
+returns this integer.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+
+
+
luaL_optlstring+[-0, +0, v] +
const char *luaL_optlstring (lua_State *L, + int arg, + const char *d, + size_t *l);+ +
+If the function argument arg is a string,
+returns this string.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+If l is not NULL,
+fills its referent with the result's length.
+If the result is NULL
+(only possible when returning d and d == NULL),
+its length is considered zero.
+
+
+
+This function uses lua_tolstring to get its result,
+so all conversions and caveats of that function apply here.
+
+
+
+
+
+
luaL_optnumber+[-0, +0, v] +
lua_Number luaL_optnumber (lua_State *L, int arg, lua_Number d);+ +
+If the function argument arg is a number,
+returns this number as a lua_Number.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+
+
+
luaL_optstring+[-0, +0, v] +
const char *luaL_optstring (lua_State *L, + int arg, + const char *d);+ +
+If the function argument arg is a string,
+returns this string.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+
+
+
luaL_prepbuffer+[-?, +?, m] +
char *luaL_prepbuffer (luaL_Buffer *B);+ +
+Equivalent to luaL_prepbuffsize
+with the predefined size LUAL_BUFFERSIZE.
+
+
+
+
+
+
luaL_prepbuffsize+[-?, +?, m] +
char *luaL_prepbuffsize (luaL_Buffer *B, size_t sz);+ +
+Returns an address to a space of size sz
+where you can copy a string to be added to buffer B
+(see luaL_Buffer).
+After copying the string into this space you must call
+luaL_addsize with the size of the string to actually add
+it to the buffer.
+
+
+
+
+
+
luaL_pushfail+[-0, +1, –] +
void luaL_pushfail (lua_State *L);+ +
+Pushes the fail value onto the stack (see §6). + + + + + +
luaL_pushresult+[-?, +1, m] +
void luaL_pushresult (luaL_Buffer *B);+ +
+Finishes the use of buffer B leaving the final string on
+the top of the stack.
+
+
+
+
+
+
luaL_pushresultsize+[-?, +1, m] +
void luaL_pushresultsize (luaL_Buffer *B, size_t sz);+ +
+Equivalent to the sequence luaL_addsize, luaL_pushresult.
+
+
+
+
+
+
luaL_ref+[-1, +0, m] +
int luaL_ref (lua_State *L, int t);+ +
+Creates and returns a reference,
+in the table at index t,
+for the object on the top of the stack (and pops the object).
+
+
+
+A reference is a unique integer key.
+As long as you do not manually add integer keys into the table t,
+luaL_ref ensures the uniqueness of the key it returns.
+You can retrieve an object referred by the reference r
+by calling lua_rawgeti(L, t, r).
+The function luaL_unref frees a reference.
+
+
+
+If the object on the top of the stack is nil,
+luaL_ref returns the constant LUA_REFNIL.
+The constant LUA_NOREF is guaranteed to be different
+from any reference returned by luaL_ref.
+
+
+
+
+
+
luaL_Regtypedef struct luaL_Reg {
+ const char *name;
+ lua_CFunction func;
+} luaL_Reg;
+
+
+Type for arrays of functions to be registered by
+luaL_setfuncs.
+name is the function name and func is a pointer to
+the function.
+Any array of luaL_Reg must end with a sentinel entry
+in which both name and func are NULL.
+
+
+
+
+
+
luaL_requiref+[-0, +1, e] +
void luaL_requiref (lua_State *L, const char *modname, + lua_CFunction openf, int glb);+ +
+If package.loaded[modname] is not true,
+calls the function openf with the string modname as an argument
+and sets the call result to package.loaded[modname],
+as if that function has been called through require.
+
+
+
+If glb is true,
+also stores the module into the global modname.
+
+
+
+Leaves a copy of the module on the stack. + + + + + +
luaL_setfuncs+[-nup, +0, m] +
void luaL_setfuncs (lua_State *L, const luaL_Reg *l, int nup);+ +
+Registers all functions in the array l
+(see luaL_Reg) into the table on the top of the stack
+(below optional upvalues, see next).
+
+
+
+When nup is not zero,
+all functions are created with nup upvalues,
+initialized with copies of the nup values
+previously pushed on the stack
+on top of the library table.
+These values are popped from the stack after the registration.
+
+
+
+A function with a NULL value represents a placeholder,
+which is filled with false.
+
+
+
+
+
+
luaL_setmetatable+[-0, +0, –] +
void luaL_setmetatable (lua_State *L, const char *tname);+ +
+Sets the metatable of the object on the top of the stack
+as the metatable associated with name tname
+in the registry (see luaL_newmetatable).
+
+
+
+
+
+
luaL_Streamtypedef struct luaL_Stream {
+ FILE *f;
+ lua_CFunction closef;
+} luaL_Stream;
+
++The standard representation for file handles +used by the standard I/O library. + + +
+A file handle is implemented as a full userdata,
+with a metatable called LUA_FILEHANDLE
+(where LUA_FILEHANDLE is a macro with the actual metatable's name).
+The metatable is created by the I/O library
+(see luaL_newmetatable).
+
+
+
+This userdata must start with the structure luaL_Stream;
+it can contain other data after this initial structure.
+The field f points to the corresponding C stream
+(or it can be NULL to indicate an incompletely created handle).
+The field closef points to a Lua function
+that will be called to close the stream
+when the handle is closed or collected;
+this function receives the file handle as its sole argument and
+must return either a true value, in case of success,
+or a false value plus an error message, in case of error.
+Once Lua calls this field,
+it changes the field value to NULL
+to signal that the handle is closed.
+
+
+
+
+
+
luaL_testudata+[-0, +0, m] +
void *luaL_testudata (lua_State *L, int arg, const char *tname);+ +
+This function works like luaL_checkudata,
+except that, when the test fails,
+it returns NULL instead of raising an error.
+
+
+
+
+
+
luaL_tolstring+[-0, +1, e] +
const char *luaL_tolstring (lua_State *L, int idx, size_t *len);+ +
+Converts any Lua value at the given index to a C string
+in a reasonable format.
+The resulting string is pushed onto the stack and also
+returned by the function (see §4.1.3).
+If len is not NULL,
+the function also sets *len with the string length.
+
+
+
+If the value has a metatable with a __tostring field,
+then luaL_tolstring calls the corresponding metamethod
+with the value as argument,
+and uses the result of the call as its result.
+
+
+
+
+
+
luaL_traceback+[-0, +1, m] +
void luaL_traceback (lua_State *L, lua_State *L1, const char *msg, + int level);+ +
+Creates and pushes a traceback of the stack L1.
+If msg is not NULL, it is appended
+at the beginning of the traceback.
+The level parameter tells at which level
+to start the traceback.
+
+
+
+
+
+
luaL_typeerror+[-0, +0, v] +
int luaL_typeerror (lua_State *L, int arg, const char *tname);+ +
+Raises a type error for the argument arg
+of the C function that called it,
+using a standard message;
+tname is a "name" for the expected type.
+This function never returns.
+
+
+
+
+
+
luaL_typename+[-0, +0, –] +
const char *luaL_typename (lua_State *L, int index);+ +
+Returns the name of the type of the value at the given index. + + + + + +
luaL_unref+[-0, +0, –] +
void luaL_unref (lua_State *L, int t, int ref);+ +
+Releases the reference ref from the table at index t
+(see luaL_ref).
+The entry is removed from the table,
+so that the referred object can be collected.
+The reference ref is also freed to be used again.
+
+
+
+If ref is LUA_NOREF or LUA_REFNIL,
+luaL_unref does nothing.
+
+
+
+
+
+
luaL_where+[-0, +1, m] +
void luaL_where (lua_State *L, int lvl);+ +
+Pushes onto the stack a string identifying the current position
+of the control at level lvl in the call stack.
+Typically this string has the following format:
+
+
+ chunkname:currentline: +
+Level 0 is the running function, +level 1 is the function that called the running function, +etc. + + +
+This function is used to build a prefix for error messages. + + + + + + + +
+The standard Lua libraries provide useful functions
+that are implemented in C through the C API.
+Some of these functions provide essential services to the language
+(e.g., type and getmetatable);
+others provide access to outside services (e.g., I/O);
+and others could be implemented in Lua itself,
+but that for different reasons
+deserve an implementation in C (e.g., table.sort).
+
+
+
+All libraries are implemented through the official C API
+and are provided as separate C modules.
+Unless otherwise noted,
+these library functions do not adjust its number of arguments
+to its expected parameters.
+For instance, a function documented as foo(arg)
+should not be called without an argument.
+
+
+
+The notation fail means a false value representing
+some kind of failure.
+(Currently, fail is equal to nil,
+but that may change in future versions.
+The recommendation is to always test the success of these functions
+with (not status), instead of (status == nil).)
+
+
+
+Currently, Lua has the following standard libraries: + +
+Except for the basic and the package libraries, +each library provides all its functions as fields of a global table +or as methods of its objects. + + +
+To have access to these libraries,
+the C host program should call the luaL_openlibs function,
+which opens all standard libraries.
+Alternatively,
+the host program can open them individually by using
+luaL_requiref to call
+luaopen_base (for the basic library),
+luaopen_package (for the package library),
+luaopen_coroutine (for the coroutine library),
+luaopen_string (for the string library),
+luaopen_utf8 (for the UTF-8 library),
+luaopen_table (for the table library),
+luaopen_math (for the mathematical library),
+luaopen_io (for the I/O library),
+luaopen_os (for the operating system library),
+and luaopen_debug (for the debug library).
+These functions are declared in lualib.h.
+
+
+
+
+
+
+The basic library provides core functions to Lua. +If you do not include this library in your application, +you should check carefully whether you need to provide +implementations for some of its facilities. + + +
+
assert (v [, message])
+Raises an error if
+the value of its argument v is false (i.e., nil or false);
+otherwise, returns all its arguments.
+In case of error,
+message is the error object;
+when absent, it defaults to "assertion failed!"
+
+
+
+
+
+
collectgarbage ([opt [, arg]])
+This function is a generic interface to the garbage collector.
+It performs different functions according to its first argument, opt:
+
+
collect":
+Performs a full garbage-collection cycle.
+This is the default option.
+stop":
+Stops automatic execution of the garbage collector.
+The collector will run only when explicitly invoked,
+until a call to restart it.
+restart":
+Restarts automatic execution of the garbage collector.
+count":
+Returns the total memory in use by Lua in Kbytes.
+The value has a fractional part,
+so that it multiplied by 1024
+gives the exact number of bytes in use by Lua.
+step":
+Performs a garbage-collection step.
+The step "size" is controlled by arg.
+With a zero value,
+the collector will perform one basic (indivisible) step.
+For non-zero values,
+the collector will perform as if that amount of memory
+(in Kbytes) had been allocated by Lua.
+Returns true if the step finished a collection cycle.
+isrunning":
+Returns a boolean that tells whether the collector is running
+(i.e., not stopped).
+incremental":
+Change the collector mode to incremental.
+This option can be followed by three numbers:
+the garbage-collector pause,
+the step multiplier,
+and the step size (see §2.5.1).
+A zero means to not change that value.
+generational":
+Change the collector mode to generational.
+This option can be followed by two numbers:
+the garbage-collector minor multiplier
+and the major multiplier (see §2.5.2).
+A zero means to not change that value.
++See §2.5 for more details about garbage collection +and some of these options. + + +
+This function should not be called by a finalizer. + + + + +
+
dofile ([filename])dofile executes the content of the standard input (stdin).
+Returns all values returned by the chunk.
+In case of errors, dofile propagates the error
+to its caller.
+(That is, dofile does not run in protected mode.)
+
+
+
+
++
error (message [, level])message as the error object.
+This function never returns.
+
+
+
+Usually, error adds some information about the error position
+at the beginning of the message, if the message is a string.
+The level argument specifies how to get the error position.
+With level 1 (the default), the error position is where the
+error function was called.
+Level 2 points the error to where the function
+that called error was called; and so on.
+Passing a level 0 avoids the addition of error position information
+to the message.
+
+
+
+
+
+
_G+
getmetatable (object)
+If object does not have a metatable, returns nil.
+Otherwise,
+if the object's metatable has a __metatable field,
+returns the associated value.
+Otherwise, returns the metatable of the given object.
+
+
+
+
+
+
ipairs (t)
+Returns three values (an iterator function, the table t, and 0)
+so that the construction
+
+
+ for i,v in ipairs(t) do body end +
+will iterate over the key–value pairs
+(1,t[1]), (2,t[2]), ...,
+up to the first absent index.
+
+
+
+
+
+
load (chunk [, chunkname [, mode [, env]]])+Loads a chunk. + + +
+If chunk is a string, the chunk is this string.
+If chunk is a function,
+load calls it repeatedly to get the chunk pieces.
+Each call to chunk must return a string that concatenates
+with previous results.
+A return of an empty string, nil, or no value signals the end of the chunk.
+
+
+
+If there are no syntactic errors,
+load returns the compiled chunk as a function;
+otherwise, it returns fail plus the error message.
+
+
+
+When you load a main chunk,
+the resulting function will always have exactly one upvalue,
+the _ENV variable (see §2.2).
+However,
+when you load a binary chunk created from a function (see string.dump),
+the resulting function can have an arbitrary number of upvalues,
+and there is no guarantee that its first upvalue will be
+the _ENV variable.
+(A non-main function may not even have an _ENV upvalue.)
+
+
+
+Regardless, if the resulting function has any upvalues,
+its first upvalue is set to the value of env,
+if that parameter is given,
+or to the value of the global environment.
+Other upvalues are initialized with nil.
+All upvalues are fresh, that is,
+they are not shared with any other function.
+
+
+
+chunkname is used as the name of the chunk for error messages
+and debug information (see §4.7).
+When absent,
+it defaults to chunk, if chunk is a string,
+or to "=(load)" otherwise.
+
+
+
+The string mode controls whether the chunk can be text or binary
+(that is, a precompiled chunk).
+It may be the string "b" (only binary chunks),
+"t" (only text chunks),
+or "bt" (both binary and text).
+The default is "bt".
+
+
+
+It is safe to load malformed binary chunks;
+load signals an appropriate error.
+However,
+Lua does not check the consistency of the code inside binary chunks;
+running maliciously crafted bytecode can crash the interpreter.
+
+
+
+
+
+
loadfile ([filename [, mode [, env]]])
+Similar to load,
+but gets the chunk from file filename
+or from the standard input,
+if no file name is given.
+
+
+
+
+
+
next (table [, index])
+Allows a program to traverse all fields of a table.
+Its first argument is a table and its second argument
+is an index in this table.
+A call to next returns the next index of the table
+and its associated value.
+When called with nil as its second argument,
+next returns an initial index
+and its associated value.
+When called with the last index,
+or with nil in an empty table,
+next returns nil.
+If the second argument is absent, then it is interpreted as nil.
+In particular,
+you can use next(t) to check whether a table is empty.
+
+
+
+The order in which the indices are enumerated is not specified, +even for numeric indices. +(To traverse a table in numerical order, +use a numerical for.) + + +
+You should not assign any value to a non-existent field in a table +during its traversal. +You may however modify existing fields. +In particular, you may set existing fields to nil. + + + + +
+
pairs (t)
+If t has a metamethod __pairs,
+calls it with t as argument and returns the first three
+results from the call.
+
+
+
+Otherwise,
+returns three values: the next function, the table t, and nil,
+so that the construction
+
+
+ for k,v in pairs(t) do body end +
+will iterate over all key–value pairs of table t.
+
+
+
+See function next for the caveats of modifying
+the table during its traversal.
+
+
+
+
+
+
pcall (f [, arg1, ···])
+Calls the function f with
+the given arguments in protected mode.
+This means that any error inside f is not propagated;
+instead, pcall catches the error
+and returns a status code.
+Its first result is the status code (a boolean),
+which is true if the call succeeds without errors.
+In such case, pcall also returns all results from the call,
+after this first result.
+In case of any error, pcall returns false plus the error object.
+Note that errors caught by pcall do not call a message handler.
+
+
+
+
+
+
print (···)stdout,
+converting each argument to a string
+following the same rules of tostring.
+
+
+
+The function print is not intended for formatted output,
+but only as a quick way to show a value,
+for instance for debugging.
+For complete control over the output,
+use string.format and io.write.
+
+
+
+
+
+
rawequal (v1, v2)v1 is equal to v2,
+without invoking the __eq metamethod.
+Returns a boolean.
+
+
+
+
++
rawget (table, index)table[index],
+without using the __index metavalue.
+table must be a table;
+index may be any value.
+
+
+
+
++
rawlen (v)v,
+which must be a table or a string,
+without invoking the __len metamethod.
+Returns an integer.
+
+
+
+
++
rawset (table, index, value)table[index] to value,
+without using the __newindex metavalue.
+table must be a table,
+index any value different from nil and NaN,
+and value any Lua value.
+
+
+
+This function returns table.
+
+
+
+
+
+
select (index, ···)
+If index is a number,
+returns all arguments after argument number index;
+a negative number indexes from the end (-1 is the last argument).
+Otherwise, index must be the string "#",
+and select returns the total number of extra arguments it received.
+
+
+
+
+
+
setmetatable (table, metatable)
+Sets the metatable for the given table.
+If metatable is nil,
+removes the metatable of the given table.
+If the original metatable has a __metatable field,
+raises an error.
+
+
+
+This function returns table.
+
+
+
+To change the metatable of other types from Lua code, +you must use the debug library (§6.10). + + + + +
+
tonumber (e [, base])
+When called with no base,
+tonumber tries to convert its argument to a number.
+If the argument is already a number or
+a string convertible to a number,
+then tonumber returns this number;
+otherwise, it returns fail.
+
+
+
+The conversion of strings can result in integers or floats, +according to the lexical conventions of Lua (see §3.1). +The string may have leading and trailing spaces and a sign. + + +
+When called with base,
+then e must be a string to be interpreted as
+an integer numeral in that base.
+The base may be any integer between 2 and 36, inclusive.
+In bases above 10, the letter 'A' (in either upper or lower case)
+represents 10, 'B' represents 11, and so forth,
+with 'Z' representing 35.
+If the string e is not a valid numeral in the given base,
+the function returns fail.
+
+
+
+
+
+
tostring (v)+Receives a value of any type and +converts it to a string in a human-readable format. + + +
+If the metatable of v has a __tostring field,
+then tostring calls the corresponding value
+with v as argument,
+and uses the result of the call as its result.
+Otherwise, if the metatable of v has a __name field
+with a string value,
+tostring may use that string in its final result.
+
+
+
+For complete control of how numbers are converted,
+use string.format.
+
+
+
+
+
+
type (v)
+Returns the type of its only argument, coded as a string.
+The possible results of this function are
+"nil" (a string, not the value nil),
+"number",
+"string",
+"boolean",
+"table",
+"function",
+"thread",
+and "userdata".
+
+
+
+
+
+
_VERSION
+A global variable (not a function) that
+holds a string containing the running Lua version.
+The current value of this variable is "Lua 5.4".
+
+
+
+
+
+
warn (msg1, ···)+Emits a warning with a message composed by the concatenation +of all its arguments (which should be strings). + + +
+By convention,
+a one-piece message starting with '@'
+is intended to be a control message,
+which is a message to the warning system itself.
+In particular, the standard warning function in Lua
+recognizes the control messages "@off",
+to stop the emission of warnings,
+and "@on", to (re)start the emission;
+it ignores unknown control messages.
+
+
+
+
+
+
xpcall (f, msgh [, arg1, ···])
+This function is similar to pcall,
+except that it sets a new message handler msgh.
+
+
+
+
+
+
+
+
+This library comprises the operations to manipulate coroutines,
+which come inside the table coroutine.
+See §2.6 for a general description of coroutines.
+
+
+
+
coroutine.close (co)
+Closes coroutine co,
+that is,
+closes all its pending to-be-closed variables
+and puts the coroutine in a dead state.
+The given coroutine must be dead or suspended.
+In case of error
+(either the original error that stopped the coroutine or
+errors in closing methods),
+returns false plus the error object;
+otherwise returns true.
+
+
+
+
+
+
coroutine.create (f)
+Creates a new coroutine, with body f.
+f must be a function.
+Returns this new coroutine,
+an object with type "thread".
+
+
+
+
+
+
coroutine.isyieldable ([co])
+Returns true when the coroutine co can yield.
+The default for co is the running coroutine.
+
+
+
+A coroutine is yieldable if it is not the main thread and +it is not inside a non-yieldable C function. + + + + +
+
coroutine.resume (co [, val1, ···])
+Starts or continues the execution of coroutine co.
+The first time you resume a coroutine,
+it starts running its body.
+The values val1, ... are passed
+as the arguments to the body function.
+If the coroutine has yielded,
+resume restarts it;
+the values val1, ... are passed
+as the results from the yield.
+
+
+
+If the coroutine runs without any errors,
+resume returns true plus any values passed to yield
+(when the coroutine yields) or any values returned by the body function
+(when the coroutine terminates).
+If there is any error,
+resume returns false plus the error message.
+
+
+
+
+
+
coroutine.running ()+Returns the running coroutine plus a boolean, +true when the running coroutine is the main one. + + + + +
+
coroutine.status (co)
+Returns the status of the coroutine co, as a string:
+"running",
+if the coroutine is running
+(that is, it is the one that called status);
+"suspended", if the coroutine is suspended in a call to yield,
+or if it has not started running yet;
+"normal" if the coroutine is active but not running
+(that is, it has resumed another coroutine);
+and "dead" if the coroutine has finished its body function,
+or if it has stopped with an error.
+
+
+
+
+
+
coroutine.wrap (f)
+Creates a new coroutine, with body f;
+f must be a function.
+Returns a function that resumes the coroutine each time it is called.
+Any arguments passed to this function behave as the
+extra arguments to resume.
+The function returns the same values returned by resume,
+except the first boolean.
+In case of error,
+the function closes the coroutine and propagates the error.
+
+
+
+
+
+
coroutine.yield (···)
+Suspends the execution of the calling coroutine.
+Any arguments to yield are passed as extra results to resume.
+
+
+
+
+
+
+
+
+The package library provides basic
+facilities for loading modules in Lua.
+It exports one function directly in the global environment:
+require.
+Everything else is exported in the table package.
+
+
+
+
require (modname)
+Loads the given module.
+The function starts by looking into the package.loaded table
+to determine whether modname is already loaded.
+If it is, then require returns the value stored
+at package.loaded[modname].
+(The absence of a second result in this case
+signals that this call did not have to load the module.)
+Otherwise, it tries to find a loader for the module.
+
+
+
+To find a loader,
+require is guided by the table package.searchers.
+Each item in this table is a search function,
+that searches for the module in a particular way.
+By changing this table,
+we can change how require looks for a module.
+The following explanation is based on the default configuration
+for package.searchers.
+
+
+
+First require queries package.preload[modname].
+If it has a value,
+this value (which must be a function) is the loader.
+Otherwise require searches for a Lua loader using the
+path stored in package.path.
+If that also fails, it searches for a C loader using the
+path stored in package.cpath.
+If that also fails,
+it tries an all-in-one loader (see package.searchers).
+
+
+
+Once a loader is found,
+require calls the loader with two arguments:
+modname and an extra value,
+a loader data,
+also returned by the searcher.
+The loader data can be any value useful to the module;
+for the default searchers,
+it indicates where the loader was found.
+(For instance, if the loader came from a file,
+this extra value is the file path.)
+If the loader returns any non-nil value,
+require assigns the returned value to package.loaded[modname].
+If the loader does not return a non-nil value and
+has not assigned any value to package.loaded[modname],
+then require assigns true to this entry.
+In any case, require returns the
+final value of package.loaded[modname].
+Besides that value, require also returns as a second result
+the loader data returned by the searcher,
+which indicates how require found the module.
+
+
+
+If there is any error loading or running the module,
+or if it cannot find any loader for the module,
+then require raises an error.
+
+
+
+
+
+
package.config+A string describing some compile-time configurations for packages. +This string is a sequence of lines: + +
\' for Windows and '/' for all other systems.;'.?'.!'.luaopen_ function name.
+Default is '-'.+
package.cpath
+A string with the path used by require
+to search for a C loader.
+
+
+
+Lua initializes the C path package.cpath in the same way
+it initializes the Lua path package.path,
+using the environment variable LUA_CPATH_5_4,
+or the environment variable LUA_CPATH,
+or a default path defined in luaconf.h.
+
+
+
+
+
+
package.loaded
+A table used by require to control which
+modules are already loaded.
+When you require a module modname and
+package.loaded[modname] is not false,
+require simply returns the value stored there.
+
+
+
+This variable is only a reference to the real table;
+assignments to this variable do not change the
+table used by require.
+The real table is stored in the C registry (see §4.3),
+indexed by the key LUA_LOADED_TABLE, a string.
+
+
+
+
+
+
package.loadlib (libname, funcname)
+Dynamically links the host program with the C library libname.
+
+
+
+If funcname is "*",
+then it only links with the library,
+making the symbols exported by the library
+available to other dynamically linked libraries.
+Otherwise,
+it looks for a function funcname inside the library
+and returns this function as a C function.
+So, funcname must follow the lua_CFunction prototype
+(see lua_CFunction).
+
+
+
+This is a low-level function.
+It completely bypasses the package and module system.
+Unlike require,
+it does not perform any path searching and
+does not automatically adds extensions.
+libname must be the complete file name of the C library,
+including if necessary a path and an extension.
+funcname must be the exact name exported by the C library
+(which may depend on the C compiler and linker used).
+
+
+
+This functionality is not supported by ISO C.
+As such, it is only available on some platforms
+(Windows, Linux, Mac OS X, Solaris, BSD,
+plus other Unix systems that support the dlfcn standard).
+
+
+
+This function is inherently insecure,
+as it allows Lua to call any function in any readable dynamic
+library in the system.
+(Lua calls any function assuming the function
+has a proper prototype and respects a proper protocol
+(see lua_CFunction).
+Therefore,
+calling an arbitrary function in an arbitrary dynamic library
+more often than not results in an access violation.)
+
+
+
+
+
+
package.path
+A string with the path used by require
+to search for a Lua loader.
+
+
+
+At start-up, Lua initializes this variable with
+the value of the environment variable LUA_PATH_5_4 or
+the environment variable LUA_PATH or
+with a default path defined in luaconf.h,
+if those environment variables are not defined.
+A ";;" in the value of the environment variable
+is replaced by the default path.
+
+
+
+
+
+
package.preload
+A table to store loaders for specific modules
+(see require).
+
+
+
+This variable is only a reference to the real table;
+assignments to this variable do not change the
+table used by require.
+The real table is stored in the C registry (see §4.3),
+indexed by the key LUA_PRELOAD_TABLE, a string.
+
+
+
+
+
+
package.searchers
+A table used by require to control how to find modules.
+
+
+
+Each entry in this table is a searcher function.
+When looking for a module,
+require calls each of these searchers in ascending order,
+with the module name (the argument given to require) as its
+sole argument.
+If the searcher finds the module,
+it returns another function, the module loader,
+plus an extra value, a loader data,
+that will be passed to that loader and
+returned as a second result by require.
+If it cannot find the module,
+it returns a string explaining why
+(or nil if it has nothing to say).
+
+
+
+Lua initializes this table with four searcher functions. + + +
+The first searcher simply looks for a loader in the
+package.preload table.
+
+
+
+The second searcher looks for a loader as a Lua library,
+using the path stored at package.path.
+The search is done as described in function package.searchpath.
+
+
+
+The third searcher looks for a loader as a C library,
+using the path given by the variable package.cpath.
+Again,
+the search is done as described in function package.searchpath.
+For instance,
+if the C path is the string
+
+
+ "./?.so;./?.dll;/usr/local/?/init.so" +
+the searcher for module foo
+will try to open the files ./foo.so, ./foo.dll,
+and /usr/local/foo/init.so, in that order.
+Once it finds a C library,
+this searcher first uses a dynamic link facility to link the
+application with the library.
+Then it tries to find a C function inside the library to
+be used as the loader.
+The name of this C function is the string "luaopen_"
+concatenated with a copy of the module name where each dot
+is replaced by an underscore.
+Moreover, if the module name has a hyphen,
+its suffix after (and including) the first hyphen is removed.
+For instance, if the module name is a.b.c-v2.1,
+the function name will be luaopen_a_b_c.
+
+
+
+The fourth searcher tries an all-in-one loader.
+It searches the C path for a library for
+the root name of the given module.
+For instance, when requiring a.b.c,
+it will search for a C library for a.
+If found, it looks into it for an open function for
+the submodule;
+in our example, that would be luaopen_a_b_c.
+With this facility, a package can pack several C submodules
+into one single library,
+with each submodule keeping its original open function.
+
+
+
+All searchers except the first one (preload) return as the extra value
+the file path where the module was found,
+as returned by package.searchpath.
+The first searcher always returns the string ":preload:".
+
+
+
+Searchers should raise no errors and have no side effects in Lua. +(They may have side effects in C, +for instance by linking the application with a library.) + + + + +
+
package.searchpath (name, path [, sep [, rep]])
+Searches for the given name in the given path.
+
+
+
+A path is a string containing a sequence of
+templates separated by semicolons.
+For each template,
+the function replaces each interrogation mark (if any)
+in the template with a copy of name
+wherein all occurrences of sep
+(a dot, by default)
+were replaced by rep
+(the system's directory separator, by default),
+and then tries to open the resulting file name.
+
+
+
+For instance, if the path is the string + +
+ "./?.lua;./?.lc;/usr/local/?/init.lua" +
+the search for the name foo.a
+will try to open the files
+./foo/a.lua, ./foo/a.lc, and
+/usr/local/foo/a/init.lua, in that order.
+
+
+
+Returns the resulting name of the first file that it can +open in read mode (after closing the file), +or fail plus an error message if none succeeds. +(This error message lists all file names it tried to open.) + + + + + + + +
+This library provides generic functions for string manipulation, +such as finding and extracting substrings, and pattern matching. +When indexing a string in Lua, the first character is at position 1 +(not at 0, as in C). +Indices are allowed to be negative and are interpreted as indexing backwards, +from the end of the string. +Thus, the last character is at position -1, and so on. + + +
+The string library provides all its functions inside the table
+string.
+It also sets a metatable for strings
+where the __index field points to the string table.
+Therefore, you can use the string functions in object-oriented style.
+For instance, string.byte(s,i)
+can be written as s:byte(i).
+
+
+
+The string library assumes one-byte character encodings. + + +
+
string.byte (s [, i [, j]])s[i],
+s[i+1], ..., s[j].
+The default value for i is 1;
+the default value for j is i.
+These indices are corrected
+following the same rules of function string.sub.
+
+
++Numeric codes are not necessarily portable across platforms. + + + + +
+
string.char (···)+Numeric codes are not necessarily portable across platforms. + + + + +
+
string.dump (function [, strip])
+Returns a string containing a binary representation
+(a binary chunk)
+of the given function,
+so that a later load on this string returns
+a copy of the function (but with new upvalues).
+If strip is a true value,
+the binary representation may not include all debug information
+about the function,
+to save space.
+
+
+
+Functions with upvalues have only their number of upvalues saved.
+When (re)loaded,
+those upvalues receive fresh instances.
+(See the load function for details about
+how these upvalues are initialized.
+You can use the debug library to serialize
+and reload the upvalues of a function
+in a way adequate to your needs.)
+
+
+
+
+
+
string.find (s, pattern [, init [, plain]])
+Looks for the first match of
+pattern (see §6.4.1) in the string s.
+If it finds a match, then find returns the indices of s
+where this occurrence starts and ends;
+otherwise, it returns fail.
+A third, optional numeric argument init specifies
+where to start the search;
+its default value is 1 and can be negative.
+A true as a fourth, optional argument plain
+turns off the pattern matching facilities,
+so the function does a plain "find substring" operation,
+with no characters in pattern being considered magic.
+
+
+
+If the pattern has captures, +then in a successful match +the captured values are also returned, +after the two indices. + + + + +
+
string.format (formatstring, ···)
+Returns a formatted version of its variable number of arguments
+following the description given in its first argument,
+which must be a string.
+The format string follows the same rules as the ISO C function sprintf.
+The only differences are that the conversion specifiers and modifiers
+F, n, *, h, L, and l are not supported
+and that there is an extra specifier, q.
+Both width and precision, when present,
+are limited to two digits.
+
+
+
+The specifier q formats booleans, nil, numbers, and strings
+in a way that the result is a valid constant in Lua source code.
+Booleans and nil are written in the obvious way
+(true, false, nil).
+Floats are written in hexadecimal,
+to preserve full precision.
+A string is written between double quotes,
+using escape sequences when necessary to ensure that
+it can safely be read back by the Lua interpreter.
+For instance, the call
+
+
+ string.format('%q', 'a string with "quotes" and \n new line')
++may produce the string: + +
+ "a string with \"quotes\" and \ + new line" +
+This specifier does not support modifiers (flags, width, precision). + + +
+The conversion specifiers
+A, a, E, e, f,
+G, and g all expect a number as argument.
+The specifiers c, d,
+i, o, u, X, and x
+expect an integer.
+When Lua is compiled with a C89 compiler,
+the specifiers A and a (hexadecimal floats)
+do not support modifiers.
+
+
+
+The specifier s expects a string;
+if its argument is not a string,
+it is converted to one following the same rules of tostring.
+If the specifier has any modifier,
+the corresponding string argument should not contain embedded zeros.
+
+
+
+The specifier p formats the pointer
+returned by lua_topointer.
+That gives a unique string identifier for tables, userdata,
+threads, strings, and functions.
+For other values (numbers, nil, booleans),
+this specifier results in a string representing
+the pointer NULL.
+
+
+
+
+
+
string.gmatch (s, pattern [, init])pattern (see §6.4.1)
+over the string s.
+If pattern specifies no captures,
+then the whole match is produced in each call.
+A third, optional numeric argument init specifies
+where to start the search;
+its default value is 1 and can be negative.
+
+
+
+As an example, the following loop
+will iterate over all the words from string s,
+printing one per line:
+
+
+ s = "hello world from Lua" + for w in string.gmatch(s, "%a+") do + print(w) + end +
+The next example collects all pairs key=value from the
+given string into a table:
+
+
+ t = {}
+ s = "from=world, to=Lua"
+ for k, v in string.gmatch(s, "(%w+)=(%w+)") do
+ t[k] = v
+ end
+
+
+
+For this function, a caret '^' at the start of a pattern does not
+work as an anchor, as this would prevent the iteration.
+
+
+
+
+
+
string.gsub (s, pattern, repl [, n])s
+in which all (or the first n, if given)
+occurrences of the pattern (see §6.4.1) have been
+replaced by a replacement string specified by repl,
+which can be a string, a table, or a function.
+gsub also returns, as its second value,
+the total number of matches that occurred.
+The name gsub comes from Global SUBstitution.
+
+
+
+If repl is a string, then its value is used for replacement.
+The character % works as an escape character:
+any sequence in repl of the form %d,
+with d between 1 and 9,
+stands for the value of the d-th captured substring;
+the sequence %0 stands for the whole match;
+the sequence %% stands for a single %.
+
+
+
+If repl is a table, then the table is queried for every match,
+using the first capture as the key.
+
+
+
+If repl is a function, then this function is called every time a
+match occurs, with all captured substrings passed as arguments,
+in order.
+
+
+
+In any case, +if the pattern specifies no captures, +then it behaves as if the whole pattern was inside a capture. + + +
+If the value returned by the table query or by the function call +is a string or a number, +then it is used as the replacement string; +otherwise, if it is false or nil, +then there is no replacement +(that is, the original match is kept in the string). + + +
+Here are some examples: + +
+ x = string.gsub("hello world", "(%w+)", "%1 %1")
+ --> x="hello hello world world"
+
+ x = string.gsub("hello world", "%w+", "%0 %0", 1)
+ --> x="hello hello world"
+
+ x = string.gsub("hello world from Lua", "(%w+)%s*(%w+)", "%2 %1")
+ --> x="world hello Lua from"
+
+ x = string.gsub("home = $HOME, user = $USER", "%$(%w+)", os.getenv)
+ --> x="home = /home/roberto, user = roberto"
+
+ x = string.gsub("4+5 = $return 4+5$", "%$(.-)%$", function (s)
+ return load(s)()
+ end)
+ --> x="4+5 = 9"
+
+ local t = {name="lua", version="5.4"}
+ x = string.gsub("$name-$version.tar.gz", "%$(%w+)", t)
+ --> x="lua-5.4.tar.gz"
+
+
+
+
++
string.len (s)
+Receives a string and returns its length.
+The empty string "" has length 0.
+Embedded zeros are counted,
+so "a\000bc\000" has length 5.
+
+
+
+
+
+
string.lower (s)+Receives a string and returns a copy of this string with all +uppercase letters changed to lowercase. +All other characters are left unchanged. +The definition of what an uppercase letter is depends on the current locale. + + + + +
+
string.match (s, pattern [, init])
+Looks for the first match of
+the pattern (see §6.4.1) in the string s.
+If it finds one, then match returns
+the captures from the pattern;
+otherwise it returns fail.
+If pattern specifies no captures,
+then the whole match is returned.
+A third, optional numeric argument init specifies
+where to start the search;
+its default value is 1 and can be negative.
+
+
+
+
+
+
string.pack (fmt, v1, v2, ···)
+Returns a binary string containing the values v1, v2, etc.
+serialized in binary form (packed)
+according to the format string fmt (see §6.4.2).
+
+
+
+
+
+
string.packsize (fmt)
+Returns the length of a string resulting from string.pack
+with the given format.
+The format string cannot have the variable-length options
+'s' or 'z' (see §6.4.2).
+
+
+
+
+
+
string.rep (s, n [, sep])
+Returns a string that is the concatenation of n copies of
+the string s separated by the string sep.
+The default value for sep is the empty string
+(that is, no separator).
+Returns the empty string if n is not positive.
+
+
+
+(Note that it is very easy to exhaust the memory of your machine +with a single call to this function.) + + + + +
+
string.reverse (s)
+Returns a string that is the string s reversed.
+
+
+
+
+
+
string.sub (s, i [, j])
+Returns the substring of s that
+starts at i and continues until j;
+i and j can be negative.
+If j is absent, then it is assumed to be equal to -1
+(which is the same as the string length).
+In particular,
+the call string.sub(s,1,j) returns a prefix of s
+with length j,
+and string.sub(s, -i) (for a positive i)
+returns a suffix of s
+with length i.
+
+
+
+If, after the translation of negative indices,
+i is less than 1,
+it is corrected to 1.
+If j is greater than the string length,
+it is corrected to that length.
+If, after these corrections,
+i is greater than j,
+the function returns the empty string.
+
+
+
+
+
+
string.unpack (fmt, s [, pos])
+Returns the values packed in string s (see string.pack)
+according to the format string fmt (see §6.4.2).
+An optional pos marks where
+to start reading in s (default is 1).
+After the read values,
+this function also returns the index of the first unread byte in s.
+
+
+
+
+
+
string.upper (s)+Receives a string and returns a copy of this string with all +lowercase letters changed to uppercase. +All other characters are left unchanged. +The definition of what a lowercase letter is depends on the current locale. + + + + + + + +
+Patterns in Lua are described by regular strings,
+which are interpreted as patterns by the pattern-matching functions
+string.find,
+string.gmatch,
+string.gsub,
+and string.match.
+This section describes the syntax and the meaning
+(that is, what they match) of these strings.
+
+
+
+
+
+
+A character class is used to represent a set of characters. +The following combinations are allowed in describing a character class: + +
^$()%.[]*+-?)
+represents the character x itself.
+.: (a dot) represents all characters.%a: represents all letters.%c: represents all control characters.%d: represents all digits.%g: represents all printable characters except space.%l: represents all lowercase letters.%p: represents all punctuation characters.%s: represents all space characters.%u: represents all uppercase letters.%w: represents all alphanumeric characters.%x: represents all hexadecimal digits.%x: (where x is any non-alphanumeric character)
+represents the character x.
+This is the standard way to escape the magic characters.
+Any non-alphanumeric character
+(including all punctuation characters, even the non-magical)
+can be preceded by a '%' to represent itself in a pattern.
+[set]:
+represents the class which is the union of all
+characters in set.
+A range of characters can be specified by
+separating the end characters of the range,
+in ascending order, with a '-'.
+All classes %x described above can also be used as
+components in set.
+All other characters in set represent themselves.
+For example, [%w_] (or [_%w])
+represents all alphanumeric characters plus the underscore,
+[0-7] represents the octal digits,
+and [0-7%l%-] represents the octal digits plus
+the lowercase letters plus the '-' character.
+
+
++You can put a closing square bracket in a set +by positioning it as the first character in the set. +You can put a hyphen in a set +by positioning it as the first or the last character in the set. +(You can also use an escape for both cases.) + + +
+The interaction between ranges and classes is not defined.
+Therefore, patterns like [%a-z] or [a-%%]
+have no meaning.
+
[^set]:
+represents the complement of set,
+where set is interpreted as above.
+
+For all classes represented by single letters (%a, %c, etc.),
+the corresponding uppercase letter represents the complement of the class.
+For instance, %S represents all non-space characters.
+
+
+
+The definitions of letter, space, and other character groups
+depend on the current locale.
+In particular, the class [a-z] may not be equivalent to %l.
+
+
+
+
+
+
+A pattern item can be + +
*',
+which matches sequences of zero or more characters in the class.
+These repetition items will always match the longest possible sequence;
++',
+which matches sequences of one or more characters in the class.
+These repetition items will always match the longest possible sequence;
+-',
+which also matches sequences of zero or more characters in the class.
+Unlike '*',
+these repetition items will always match the shortest possible sequence;
+?',
+which matches zero or one occurrence of a character in the class.
+It always matches one occurrence if possible;
+%n, for n between 1 and 9;
+such item matches a substring equal to the n-th captured string
+(see below);
+%bxy, where x and y are two distinct characters;
+such item matches strings that start with x, end with y,
+and where the x and y are balanced.
+This means that, if one reads the string from left to right,
+counting +1 for an x and -1 for a y,
+the ending y is the first y where the count reaches 0.
+For instance, the item %b() matches expressions with
+balanced parentheses.
+%f[set], a frontier pattern;
+such item matches an empty string at any position such that
+the next character belongs to set
+and the previous character does not belong to set.
+The set set is interpreted as previously described.
+The beginning and the end of the subject are handled as if
+they were the character '\0'.
+
+A pattern is a sequence of pattern items.
+A caret '^' at the beginning of a pattern anchors the match at the
+beginning of the subject string.
+A '$' at the end of a pattern anchors the match at the
+end of the subject string.
+At other positions,
+'^' and '$' have no special meaning and represent themselves.
+
+
+
+
+
+
+A pattern can contain sub-patterns enclosed in parentheses;
+they describe captures.
+When a match succeeds, the substrings of the subject string
+that match captures are stored (captured) for future use.
+Captures are numbered according to their left parentheses.
+For instance, in the pattern "(a*(.)%w(%s*))",
+the part of the string matching "a*(.)%w(%s*)" is
+stored as the first capture, and therefore has number 1;
+the character matching "." is captured with number 2,
+and the part matching "%s*" has number 3.
+
+
+
+As a special case, the capture () captures
+the current string position (a number).
+For instance, if we apply the pattern "()aa()" on the
+string "flaaap", there will be two captures: 3 and 5.
+
+
+
+
+
+
+The function string.gsub and the iterator string.gmatch
+match multiple occurrences of the given pattern in the subject.
+For these functions,
+a new match is considered valid only
+if it ends at least one byte after the end of the previous match.
+In other words, the pattern machine never accepts the
+empty string as a match immediately after another match.
+As an example,
+consider the results of the following code:
+
+
+ > string.gsub("abc", "()a*()", print);
+ --> 1 2
+ --> 3 3
+ --> 4 4
+
+The second and third results come from Lua matching an empty
+string after 'b' and another one after 'c'.
+Lua does not match an empty string after 'a',
+because it would end at the same position of the previous match.
+
+
+
+
+
+
+
+
+The first argument to string.pack,
+string.packsize, and string.unpack
+is a format string,
+which describes the layout of the structure being created or read.
+
+
+
+A format string is a sequence of conversion options. +The conversion options are as follows: + +
<: sets little endian>: sets big endian=: sets native endian![n]: sets maximum alignment to n
+(default is native alignment)b: a signed byte (char)B: an unsigned byte (char)h: a signed short (native size)H: an unsigned short (native size)l: a signed long (native size)L: an unsigned long (native size)j: a lua_IntegerJ: a lua_UnsignedT: a size_t (native size)i[n]: a signed int with n bytes
+(default is native size)I[n]: an unsigned int with n bytes
+(default is native size)f: a float (native size)d: a double (native size)n: a lua_Numbercn: a fixed-sized string with n bytesz: a zero-terminated strings[n]: a string preceded by its length
+coded as an unsigned integer with n bytes
+(default is a size_t)x: one byte of paddingXop: an empty item that aligns
+according to option op
+(which is otherwise ignored) ': (space) ignored
+(A "[n]" means an optional integral numeral.)
+Except for padding, spaces, and configurations
+(options "xX <=>!"),
+each option corresponds to an argument in string.pack
+or a result in string.unpack.
+
+
+
+For options "!n", "sn", "in", and "In",
+n can be any integer between 1 and 16.
+All integral options check overflows;
+string.pack checks whether the given value fits in the given size;
+string.unpack checks whether the read value fits in a Lua integer.
+For the unsigned options,
+Lua integers are treated as unsigned values too.
+
+
+
+Any format string starts as if prefixed by "!1=",
+that is,
+with maximum alignment of 1 (no alignment)
+and native endianness.
+
+
+
+Native endianness assumes that the whole system is +either big or little endian. +The packing functions will not emulate correctly the behavior +of mixed-endian formats. + + +
+Alignment works as follows:
+For each option,
+the format gets extra padding until the data starts
+at an offset that is a multiple of the minimum between the
+option size and the maximum alignment;
+this minimum must be a power of 2.
+Options "c" and "z" are not aligned;
+option "s" follows the alignment of its starting integer.
+
+
+
+All padding is filled with zeros by string.pack
+and ignored by string.unpack.
+
+
+
+
+
+
+
+
+This library provides basic support for UTF-8 encoding.
+It provides all its functions inside the table utf8.
+This library does not provide any support for Unicode other
+than the handling of the encoding.
+Any operation that needs the meaning of a character,
+such as character classification, is outside its scope.
+
+
+
+Unless stated otherwise, +all functions that expect a byte position as a parameter +assume that the given position is either the start of a byte sequence +or one plus the length of the subject string. +As in the string library, +negative indices count from the end of the string. + + +
+Functions that create byte sequences
+accept all values up to 0x7FFFFFFF,
+as defined in the original UTF-8 specification;
+that implies byte sequences of up to six bytes.
+
+
+
+Functions that interpret byte sequences only accept
+valid sequences (well formed and not overlong).
+By default, they only accept byte sequences
+that result in valid Unicode code points,
+rejecting values greater than 10FFFF and surrogates.
+A boolean argument lax, when available,
+lifts these checks,
+so that all values up to 0x7FFFFFFF are accepted.
+(Not well formed and overlong sequences are still rejected.)
+
+
+
+
utf8.char (···)+Receives zero or more integers, +converts each one to its corresponding UTF-8 byte sequence +and returns a string with the concatenation of all these sequences. + + + + +
+
utf8.charpattern
+The pattern (a string, not a function) "[\0-\x7F\xC2-\xFD][\x80-\xBF]*"
+(see §6.4.1),
+which matches exactly one UTF-8 byte sequence,
+assuming that the subject is a valid UTF-8 string.
+
+
+
+
+
+
utf8.codes (s [, lax])+Returns values so that the construction + +
+ for p, c in utf8.codes(s) do body end +
+will iterate over all UTF-8 characters in string s,
+with p being the position (in bytes) and c the code point
+of each character.
+It raises an error if it meets any invalid byte sequence.
+
+
+
+
+
+
utf8.codepoint (s [, i [, j [, lax]]])
+Returns the code points (as integers) from all characters in s
+that start between byte position i and j (both included).
+The default for i is 1 and for j is i.
+It raises an error if it meets any invalid byte sequence.
+
+
+
+
+
+
utf8.len (s [, i [, j [, lax]]])
+Returns the number of UTF-8 characters in string s
+that start between positions i and j (both inclusive).
+The default for i is 1 and for j is -1.
+If it finds any invalid byte sequence,
+returns fail plus the position of the first invalid byte.
+
+
+
+
+
+
utf8.offset (s, n [, i])
+Returns the position (in bytes) where the encoding of the
+n-th character of s
+(counting from position i) starts.
+A negative n gets characters before position i.
+The default for i is 1 when n is non-negative
+and #s + 1 otherwise,
+so that utf8.offset(s, -n) gets the offset of the
+n-th character from the end of the string.
+If the specified character is neither in the subject
+nor right after its end,
+the function returns fail.
+
+
+
+As a special case,
+when n is 0 the function returns the start of the encoding
+of the character that contains the i-th byte of s.
+
+
+
+This function assumes that s is a valid UTF-8 string.
+
+
+
+
+
+
+
+
+This library provides generic functions for table manipulation.
+It provides all its functions inside the table table.
+
+
+
+Remember that, whenever an operation needs the length of a table, +all caveats about the length operator apply (see §3.4.7). +All functions ignore non-numeric keys +in the tables given as arguments. + + +
+
table.concat (list [, sep [, i [, j]]])
+Given a list where all elements are strings or numbers,
+returns the string list[i]..sep..list[i+1] ··· sep..list[j].
+The default value for sep is the empty string,
+the default for i is 1,
+and the default for j is #list.
+If i is greater than j, returns the empty string.
+
+
+
+
+
+
table.insert (list, [pos,] value)
+Inserts element value at position pos in list,
+shifting up the elements
+list[pos], list[pos+1], ···, list[#list].
+The default value for pos is #list+1,
+so that a call table.insert(t,x) inserts x at the end
+of the list t.
+
+
+
+
+
+
table.move (a1, f, e, t [,a2])
+Moves elements from the table a1 to the table a2,
+performing the equivalent to the following
+multiple assignment:
+a2[t],··· = a1[f],···,a1[e].
+The default for a2 is a1.
+The destination range can overlap with the source range.
+The number of elements to be moved must fit in a Lua integer.
+
+
+
+Returns the destination table a2.
+
+
+
+
+
+
table.pack (···)
+Returns a new table with all arguments stored into keys 1, 2, etc.
+and with a field "n" with the total number of arguments.
+Note that the resulting table may not be a sequence,
+if some arguments are nil.
+
+
+
+
+
+
table.remove (list [, pos])
+Removes from list the element at position pos,
+returning the value of the removed element.
+When pos is an integer between 1 and #list,
+it shifts down the elements
+list[pos+1], list[pos+2], ···, list[#list]
+and erases element list[#list];
+The index pos can also be 0 when #list is 0,
+or #list + 1.
+
+
+
+The default value for pos is #list,
+so that a call table.remove(l) removes the last element
+of the list l.
+
+
+
+
+
+
table.sort (list [, comp])
+Sorts the list elements in a given order, in-place,
+from list[1] to list[#list].
+If comp is given,
+then it must be a function that receives two list elements
+and returns true when the first element must come
+before the second in the final order,
+so that, after the sort,
+i <= j implies not comp(list[j],list[i]).
+If comp is not given,
+then the standard Lua operator < is used instead.
+
+
+
+The comp function must define a consistent order;
+more formally, the function must define a strict weak order.
+(A weak order is similar to a total order,
+but it can equate different elements for comparison purposes.)
+
+
+
+The sort algorithm is not stable: +Different elements considered equal by the given order +may have their relative positions changed by the sort. + + + + +
+
table.unpack (list [, i [, j]])+Returns the elements from the given list. +This function is equivalent to + +
+ return list[i], list[i+1], ···, list[j] +
+By default, i is 1 and j is #list.
+
+
+
+
+
+
+
+
+This library provides basic mathematical functions.
+It provides all its functions and constants inside the table math.
+Functions with the annotation "integer/float" give
+integer results for integer arguments
+and float results for non-integer arguments.
+The rounding functions
+math.ceil, math.floor, and math.modf
+return an integer when the result fits in the range of an integer,
+or a float otherwise.
+
+
+
+
math.abs (x)
+Returns the maximum value between x and -x. (integer/float)
+
+
+
+
+
+
math.acos (x)
+Returns the arc cosine of x (in radians).
+
+
+
+
+
+
math.asin (x)
+Returns the arc sine of x (in radians).
+
+
+
+
+
+
math.atan (y [, x])
+
+Returns the arc tangent of y/x (in radians),
+using the signs of both arguments to find the
+quadrant of the result.
+It also handles correctly the case of x being zero.
+
+
+
+The default value for x is 1,
+so that the call math.atan(y)
+returns the arc tangent of y.
+
+
+
+
+
+
math.ceil (x)
+Returns the smallest integral value greater than or equal to x.
+
+
+
+
+
+
math.cos (x)
+Returns the cosine of x (assumed to be in radians).
+
+
+
+
+
+
math.deg (x)
+Converts the angle x from radians to degrees.
+
+
+
+
+
+
math.exp (x)
+Returns the value ex
+(where e is the base of natural logarithms).
+
+
+
+
+
+
math.floor (x)
+Returns the largest integral value less than or equal to x.
+
+
+
+
+
+
math.fmod (x, y)
+Returns the remainder of the division of x by y
+that rounds the quotient towards zero. (integer/float)
+
+
+
+
+
+
math.huge
+The float value HUGE_VAL,
+a value greater than any other numeric value.
+
+
+
+
+
+
math.log (x [, base])
+Returns the logarithm of x in the given base.
+The default for base is e
+(so that the function returns the natural logarithm of x).
+
+
+
+
+
+
math.max (x, ···)
+Returns the argument with the maximum value,
+according to the Lua operator <.
+
+
+
+
+
+
math.maxinteger+
math.min (x, ···)
+Returns the argument with the minimum value,
+according to the Lua operator <.
+
+
+
+
+
+
math.mininteger+
math.modf (x)
+Returns the integral part of x and the fractional part of x.
+Its second result is always a float.
+
+
+
+
+
+
math.pi+The value of π. + + + + +
+
math.rad (x)
+Converts the angle x from degrees to radians.
+
+
+
+
+
+
math.random ([m [, n]])
+When called without arguments,
+returns a pseudo-random float with uniform distribution
+in the range [0,1).
+When called with two integers m and n,
+math.random returns a pseudo-random integer
+with uniform distribution in the range [m, n].
+The call math.random(n), for a positive n,
+is equivalent to math.random(1,n).
+The call math.random(0) produces an integer with
+all bits (pseudo)random.
+
+
+
+This function uses the xoshiro256** algorithm to produce
+pseudo-random 64-bit integers,
+which are the results of calls with argument 0.
+Other results (ranges and floats)
+are unbiased extracted from these integers.
+
+
+
+Lua initializes its pseudo-random generator with the equivalent of
+a call to math.randomseed with no arguments,
+so that math.random should generate
+different sequences of results each time the program runs.
+
+
+
+
+
+
math.randomseed ([x [, y]])
+When called with at least one argument,
+the integer parameters x and y are
+joined into a 128-bit seed that
+is used to reinitialize the pseudo-random generator;
+equal seeds produce equal sequences of numbers.
+The default for y is zero.
+
+
+
+When called with no arguments, +Lua generates a seed with +a weak attempt for randomness. + + +
+This function returns the two seed components +that were effectively used, +so that setting them again repeats the sequence. + + +
+To ensure a required level of randomness to the initial state
+(or contrarily, to have a deterministic sequence,
+for instance when debugging a program),
+you should call math.randomseed with explicit arguments.
+
+
+
+
+
+
math.sin (x)
+Returns the sine of x (assumed to be in radians).
+
+
+
+
+
+
math.sqrt (x)
+Returns the square root of x.
+(You can also use the expression x^0.5 to compute this value.)
+
+
+
+
+
+
math.tan (x)
+Returns the tangent of x (assumed to be in radians).
+
+
+
+
+
+
math.tointeger (x)
+If the value x is convertible to an integer,
+returns that integer.
+Otherwise, returns fail.
+
+
+
+
+
+
math.type (x)
+Returns "integer" if x is an integer,
+"float" if it is a float,
+or fail if x is not a number.
+
+
+
+
+
+
math.ult (m, n)
+Returns a boolean,
+true if and only if integer m is below integer n when
+they are compared as unsigned integers.
+
+
+
+
+
+
+
+
+The I/O library provides two different styles for file manipulation. +The first one uses implicit file handles; +that is, there are operations to set a default input file and a +default output file, +and all input/output operations are done over these default files. +The second style uses explicit file handles. + + +
+When using implicit file handles,
+all operations are supplied by table io.
+When using explicit file handles,
+the operation io.open returns a file handle
+and then all operations are supplied as methods of the file handle.
+
+
+
+The metatable for file handles provides metamethods
+for __gc and __close that try
+to close the file when called.
+
+
+
+The table io also provides
+three predefined file handles with their usual meanings from C:
+io.stdin, io.stdout, and io.stderr.
+The I/O library never closes these files.
+
+
+
+Unless otherwise stated,
+all I/O functions return fail on failure,
+plus an error message as a second result and
+a system-dependent error code as a third result,
+and some non-false value on success.
+On non-POSIX systems,
+the computation of the error message and error code
+in case of errors
+may be not thread safe,
+because they rely on the global C variable errno.
+
+
+
+
io.close ([file])
+Equivalent to file:close().
+Without a file, closes the default output file.
+
+
+
+
+
+
io.flush ()
+Equivalent to io.output():flush().
+
+
+
+
+
+
io.input ([file])+When called with a file name, it opens the named file (in text mode), +and sets its handle as the default input file. +When called with a file handle, +it simply sets this file handle as the default input file. +When called without arguments, +it returns the current default input file. + + +
+In case of errors this function raises the error, +instead of returning an error code. + + + + +
+
io.lines ([filename, ···])
+Opens the given file name in read mode
+and returns an iterator function that
+works like file:lines(···) over the opened file.
+When the iterator function fails to read any value,
+it automatically closes the file.
+Besides the iterator function,
+io.lines returns three other values:
+two nil values as placeholders,
+plus the created file handle.
+Therefore, when used in a generic for loop,
+the file is closed also if the loop is interrupted by an
+error or a break.
+
+
+
+The call io.lines() (with no file name) is equivalent
+to io.input():lines("l");
+that is, it iterates over the lines of the default input file.
+In this case, the iterator does not close the file when the loop ends.
+
+
+
+In case of errors opening the file, +this function raises the error, +instead of returning an error code. + + + + +
+
io.open (filename [, mode])
+This function opens a file,
+in the mode specified in the string mode.
+In case of success,
+it returns a new file handle.
+
+
+
+The mode string can be any of the following:
+
+
r": read mode (the default);w": write mode;a": append mode;r+": update mode, all previous data is preserved;w+": update mode, all previous data is erased;a+": append update mode, previous data is preserved,
+ writing is only allowed at the end of file.
+The mode string can also have a 'b' at the end,
+which is needed in some systems to open the file in binary mode.
+
+
+
+
+
+
io.output ([file])
+Similar to io.input, but operates over the default output file.
+
+
+
+
+
+
io.popen (prog [, mode])+This function is system dependent and is not available +on all platforms. + + +
+Starts the program prog in a separated process and returns
+a file handle that you can use to read data from this program
+(if mode is "r", the default)
+or to write data to this program
+(if mode is "w").
+
+
+
+
+
+
io.read (···)
+Equivalent to io.input():read(···).
+
+
+
+
+
+
io.tmpfile ()+In case of success, +returns a handle for a temporary file. +This file is opened in update mode +and it is automatically removed when the program ends. + + + + +
+
io.type (obj)
+Checks whether obj is a valid file handle.
+Returns the string "file" if obj is an open file handle,
+"closed file" if obj is a closed file handle,
+or fail if obj is not a file handle.
+
+
+
+
+
+
io.write (···)
+Equivalent to io.output():write(···).
+
+
+
+
+
+
file:close ()
+Closes file.
+Note that files are automatically closed when
+their handles are garbage collected,
+but that takes an unpredictable amount of time to happen.
+
+
+
+When closing a file handle created with io.popen,
+file:close returns the same values
+returned by os.execute.
+
+
+
+
+
+
file:flush ()
+Saves any written data to file.
+
+
+
+
+
+
file:lines (···)
+Returns an iterator function that,
+each time it is called,
+reads the file according to the given formats.
+When no format is given,
+uses "l" as a default.
+As an example, the construction
+
+
+ for c in file:lines(1) do body end +
+will iterate over all characters of the file,
+starting at the current position.
+Unlike io.lines, this function does not close the file
+when the loop ends.
+
+
+
+
+
+
file:read (···)
+Reads the file file,
+according to the given formats, which specify what to read.
+For each format,
+the function returns a string or a number with the characters read,
+or fail if it cannot read data with the specified format.
+(In this latter case,
+the function does not read subsequent formats.)
+When called without arguments,
+it uses a default format that reads the next line
+(see below).
+
+
+
+The available formats are + +
n":
+reads a numeral and returns it as a float or an integer,
+following the lexical conventions of Lua.
+(The numeral may have leading whitespaces and a sign.)
+This format always reads the longest input sequence that
+is a valid prefix for a numeral;
+if that prefix does not form a valid numeral
+(e.g., an empty string, "0x", or "3.4e-")
+or it is too long (more than 200 characters),
+it is discarded and the format returns fail.
+a":
+reads the whole file, starting at the current position.
+On end of file, it returns the empty string;
+this format never fails.
+l":
+reads the next line skipping the end of line,
+returning fail on end of file.
+This is the default format.
+L":
+reads the next line keeping the end-of-line character (if present),
+returning fail on end of file.
+number is zero,
+it reads nothing and returns an empty string,
+or fail on end of file.
+
+The formats "l" and "L" should be used only for text files.
+
+
+
+
+
+
file:seek ([whence [, offset]])
+Sets and gets the file position,
+measured from the beginning of the file,
+to the position given by offset plus a base
+specified by the string whence, as follows:
+
+
set": base is position 0 (beginning of the file);cur": base is current position;end": base is end of file;
+In case of success, seek returns the final file position,
+measured in bytes from the beginning of the file.
+If seek fails, it returns fail,
+plus a string describing the error.
+
+
+
+The default value for whence is "cur",
+and for offset is 0.
+Therefore, the call file:seek() returns the current
+file position, without changing it;
+the call file:seek("set") sets the position to the
+beginning of the file (and returns 0);
+and the call file:seek("end") sets the position to the
+end of the file, and returns its size.
+
+
+
+
+
+
file:setvbuf (mode [, size])+Sets the buffering mode for a file. +There are three available modes: + +
no": no buffering.full": full buffering.line": line buffering.
+For the last two cases,
+size is a hint for the size of the buffer, in bytes.
+The default is an appropriate size.
+
+
+
+The specific behavior of each mode is non portable;
+check the underlying ISO C function setvbuf in your platform for
+more details.
+
+
+
+
+
+
file:write (···)
+Writes the value of each of its arguments to file.
+The arguments must be strings or numbers.
+
+
+
+In case of success, this function returns file.
+
+
+
+
+
+
+
+
+This library is implemented through table os.
+
+
+
+
os.clock ()
+Returns an approximation of the amount in seconds of CPU time
+used by the program,
+as returned by the underlying ISO C function clock.
+
+
+
+
+
+
os.date ([format [, time]])
+Returns a string or a table containing date and time,
+formatted according to the given string format.
+
+
+
+If the time argument is present,
+this is the time to be formatted
+(see the os.time function for a description of this value).
+Otherwise, date formats the current time.
+
+
+
+If format starts with '!',
+then the date is formatted in Coordinated Universal Time.
+After this optional character,
+if format is the string "*t",
+then date returns a table with the following fields:
+year, month (1–12), day (1–31),
+hour (0–23), min (0–59),
+sec (0–61, due to leap seconds),
+wday (weekday, 1–7, Sunday is 1),
+yday (day of the year, 1–366),
+and isdst (daylight saving flag, a boolean).
+This last field may be absent
+if the information is not available.
+
+
+
+If format is not "*t",
+then date returns the date as a string,
+formatted according to the same rules as the ISO C function strftime.
+
+
+
+If format is absent, it defaults to "%c",
+which gives a human-readable date and time representation
+using the current locale.
+
+
+
+On non-POSIX systems,
+this function may be not thread safe
+because of its reliance on C function gmtime and C function localtime.
+
+
+
+
+
+
os.difftime (t2, t1)
+Returns the difference, in seconds,
+from time t1 to time t2
+(where the times are values returned by os.time).
+In POSIX, Windows, and some other systems,
+this value is exactly t2-t1.
+
+
+
+
+
+
os.execute ([command])
+This function is equivalent to the ISO C function system.
+It passes command to be executed by an operating system shell.
+Its first result is true
+if the command terminated successfully,
+or fail otherwise.
+After this first result
+the function returns a string plus a number,
+as follows:
+
+
exit":
+the command terminated normally;
+the following number is the exit status of the command.
+signal":
+the command was terminated by a signal;
+the following number is the signal that terminated the command.
+
+When called without a command,
+os.execute returns a boolean that is true if a shell is available.
+
+
+
+
+
+
os.exit ([code [, close]])
+Calls the ISO C function exit to terminate the host program.
+If code is true,
+the returned status is EXIT_SUCCESS;
+if code is false,
+the returned status is EXIT_FAILURE;
+if code is a number,
+the returned status is this number.
+The default value for code is true.
+
+
+
+If the optional second argument close is true,
+the function closes the Lua state before exiting (see lua_close).
+
+
+
+
+
+
os.getenv (varname)
+Returns the value of the process environment variable varname
+or fail if the variable is not defined.
+
+
+
+
+
+
os.remove (filename)+Deletes the file (or empty directory, on POSIX systems) +with the given name. +If this function fails, it returns fail +plus a string describing the error and the error code. +Otherwise, it returns true. + + + + +
+
os.rename (oldname, newname)
+Renames the file or directory named oldname to newname.
+If this function fails, it returns fail,
+plus a string describing the error and the error code.
+Otherwise, it returns true.
+
+
+
+
+
+
os.setlocale (locale [, category])
+Sets the current locale of the program.
+locale is a system-dependent string specifying a locale;
+category is an optional string describing which category to change:
+"all", "collate", "ctype",
+"monetary", "numeric", or "time";
+the default category is "all".
+The function returns the name of the new locale,
+or fail if the request cannot be honored.
+
+
+
+If locale is the empty string,
+the current locale is set to an implementation-defined native locale.
+If locale is the string "C",
+the current locale is set to the standard C locale.
+
+
+
+When called with nil as the first argument, +this function only returns the name of the current locale +for the given category. + + +
+This function may be not thread safe
+because of its reliance on C function setlocale.
+
+
+
+
+
+
os.time ([table])
+Returns the current time when called without arguments,
+or a time representing the local date and time specified by the given table.
+This table must have fields year, month, and day,
+and may have fields
+hour (default is 12),
+min (default is 0),
+sec (default is 0),
+and isdst (default is nil).
+Other fields are ignored.
+For a description of these fields, see the os.date function.
+
+
+
+When the function is called,
+the values in these fields do not need to be inside their valid ranges.
+For instance, if sec is -10,
+it means 10 seconds before the time specified by the other fields;
+if hour is 1000,
+it means 1000 hours after the time specified by the other fields.
+
+
+
+The returned value is a number, whose meaning depends on your system.
+In POSIX, Windows, and some other systems,
+this number counts the number
+of seconds since some given start time (the "epoch").
+In other systems, the meaning is not specified,
+and the number returned by time can be used only as an argument to
+os.date and os.difftime.
+
+
+
+When called with a table,
+os.time also normalizes all the fields
+documented in the os.date function,
+so that they represent the same time as before the call
+but with values inside their valid ranges.
+
+
+
+
+
+
os.tmpname ()+Returns a string with a file name that can +be used for a temporary file. +The file must be explicitly opened before its use +and explicitly removed when no longer needed. + + +
+In POSIX systems, +this function also creates a file with that name, +to avoid security risks. +(Someone else might create the file with wrong permissions +in the time between getting the name and creating the file.) +You still have to open the file to use it +and to remove it (even if you do not use it). + + +
+When possible,
+you may prefer to use io.tmpfile,
+which automatically removes the file when the program ends.
+
+
+
+
+
+
+
+
+This library provides +the functionality of the debug interface (§4.7) to Lua programs. +You should exert care when using this library. +Several of its functions +violate basic assumptions about Lua code +(e.g., that variables local to a function +cannot be accessed from outside; +that userdata metatables cannot be changed by Lua code; +that Lua programs do not crash) +and therefore can compromise otherwise secure code. +Moreover, some functions in this library may be slow. + + +
+All functions in this library are provided
+inside the debug table.
+All functions that operate over a thread
+have an optional first argument which is the
+thread to operate over.
+The default is always the current thread.
+
+
+
+
debug.debug ()
+Enters an interactive mode with the user,
+running each string that the user enters.
+Using simple commands and other debug facilities,
+the user can inspect global and local variables,
+change their values, evaluate expressions, and so on.
+A line containing only the word cont finishes this function,
+so that the caller continues its execution.
+
+
+
+Note that commands for debug.debug are not lexically nested
+within any function and so have no direct access to local variables.
+
+
+
+
+
+
debug.gethook ([thread])
+Returns the current hook settings of the thread, as three values:
+the current hook function, the current hook mask,
+and the current hook count,
+as set by the debug.sethook function.
+
+
+
+Returns fail if there is no active hook. + + + + +
+
debug.getinfo ([thread,] f [, what])
+Returns a table with information about a function.
+You can give the function directly
+or you can give a number as the value of f,
+which means the function running at level f of the call stack
+of the given thread:
+level 0 is the current function (getinfo itself);
+level 1 is the function that called getinfo
+(except for tail calls, which do not count in the stack);
+and so on.
+If f is a number greater than the number of active functions,
+then getinfo returns fail.
+
+
+
+The returned table can contain all the fields returned by lua_getinfo,
+with the string what describing which fields to fill in.
+The default for what is to get all information available,
+except the table of valid lines.
+The option 'f'
+adds a field named func with the function itself.
+The option 'L' adds a field named activelines
+with the table of valid lines,
+provided the function is a Lua function.
+If the function has no debug information,
+the table is empty.
+
+
+
+For instance, the expression debug.getinfo(1,"n").name returns
+a name for the current function,
+if a reasonable name can be found,
+and the expression debug.getinfo(print)
+returns a table with all available information
+about the print function.
+
+
+
+
+
+
debug.getlocal ([thread,] f, local)
+This function returns the name and the value of the local variable
+with index local of the function at level f of the stack.
+This function accesses not only explicit local variables,
+but also parameters and temporary values.
+
+
+
+The first parameter or local variable has index 1, and so on,
+following the order that they are declared in the code,
+counting only the variables that are active
+in the current scope of the function.
+Compile-time constants may not appear in this listing,
+if they were optimized away by the compiler.
+Negative indices refer to vararg arguments;
+-1 is the first vararg argument.
+The function returns fail
+if there is no variable with the given index,
+and raises an error when called with a level out of range.
+(You can call debug.getinfo to check whether the level is valid.)
+
+
+
+Variable names starting with '(' (open parenthesis)
+represent variables with no known names
+(internal variables such as loop control variables,
+and variables from chunks saved without debug information).
+
+
+
+The parameter f may also be a function.
+In that case, getlocal returns only the name of function parameters.
+
+
+
+
+
+
debug.getmetatable (value)
+Returns the metatable of the given value
+or nil if it does not have a metatable.
+
+
+
+
+
+
debug.getregistry ()+Returns the registry table (see §4.3). + + + + +
+
debug.getupvalue (f, up)
+This function returns the name and the value of the upvalue
+with index up of the function f.
+The function returns fail
+if there is no upvalue with the given index.
+
+
+
+(For Lua functions, +upvalues are the external local variables that the function uses, +and that are consequently included in its closure.) + + +
+For C functions, this function uses the empty string ""
+as a name for all upvalues.
+
+
+
+Variable name '?' (interrogation mark)
+represents variables with no known names
+(variables from chunks saved without debug information).
+
+
+
+
+
+
debug.getuservalue (u, n)
+Returns the n-th user value associated
+to the userdata u plus a boolean,
+false if the userdata does not have that value.
+
+
+
+
+
+
debug.sethook ([thread,] hook, mask [, count])
+Sets the given function as the debug hook.
+The string mask and the number count describe
+when the hook will be called.
+The string mask may have any combination of the following characters,
+with the given meaning:
+
+
c': the hook is called every time Lua calls a function;r': the hook is called every time Lua returns from a function;l': the hook is called every time Lua enters a new line of code.
+Moreover,
+with a count different from zero,
+the hook is called also after every count instructions.
+
+
+
+When called without arguments,
+debug.sethook turns off the hook.
+
+
+
+When the hook is called, its first parameter is a string
+describing the event that has triggered its call:
+"call", "tail call", "return",
+"line", and "count".
+For line events,
+the hook also gets the new line number as its second parameter.
+Inside a hook,
+you can call getinfo with level 2 to get more information about
+the running function.
+(Level 0 is the getinfo function,
+and level 1 is the hook function.)
+
+
+
+
+
+
debug.setlocal ([thread,] level, local, value)
+This function assigns the value value to the local variable
+with index local of the function at level level of the stack.
+The function returns fail if there is no local
+variable with the given index,
+and raises an error when called with a level out of range.
+(You can call getinfo to check whether the level is valid.)
+Otherwise, it returns the name of the local variable.
+
+
+
+See debug.getlocal for more information about
+variable indices and names.
+
+
+
+
+
+
debug.setmetatable (value, table)
+Sets the metatable for the given value to the given table
+(which can be nil).
+Returns value.
+
+
+
+
+
+
debug.setupvalue (f, up, value)
+This function assigns the value value to the upvalue
+with index up of the function f.
+The function returns fail if there is no upvalue
+with the given index.
+Otherwise, it returns the name of the upvalue.
+
+
+
+See debug.getupvalue for more information about upvalues.
+
+
+
+
+
+
debug.setuservalue (udata, value, n)
+Sets the given value as
+the n-th user value associated to the given udata.
+udata must be a full userdata.
+
+
+
+Returns udata,
+or fail if the userdata does not have that value.
+
+
+
+
+
+
debug.traceback ([thread,] [message [, level]])
+If message is present but is neither a string nor nil,
+this function returns message without further processing.
+Otherwise,
+it returns a string with a traceback of the call stack.
+The optional message string is appended
+at the beginning of the traceback.
+An optional level number tells at which level
+to start the traceback
+(default is 1, the function calling traceback).
+
+
+
+
+
+
debug.upvalueid (f, n)
+Returns a unique identifier (as a light userdata)
+for the upvalue numbered n
+from the given function.
+
+
+
+These unique identifiers allow a program to check whether different +closures share upvalues. +Lua closures that share an upvalue +(that is, that access a same external local variable) +will return identical ids for those upvalue indices. + + + + +
+
debug.upvaluejoin (f1, n1, f2, n2)
+Make the n1-th upvalue of the Lua closure f1
+refer to the n2-th upvalue of the Lua closure f2.
+
+
+
+
+
+
+
+
+Although Lua has been designed as an extension language,
+to be embedded in a host C program,
+it is also frequently used as a standalone language.
+An interpreter for Lua as a standalone language,
+called simply lua,
+is provided with the standard distribution.
+The standalone interpreter includes
+all standard libraries.
+Its usage is:
+
+
+ lua [options] [script [args]] +
+The options are: + +
-e stat: execute string stat;-i: enter interactive mode after running script;-l mod: "require" mod and assign the
+ result to global mod;-l g=mod: "require" mod and assign the
+ result to global g;-v: print version information;-E: ignore environment variables;-W: turn warnings on;--: stop handling options;-: execute stdin as a file and stop handling options.
+(The form -l g=mod was introduced in release 5.4.4.)
+
+
+
+After handling its options, lua runs the given script.
+When called without arguments,
+lua behaves as lua -v -i
+when the standard input (stdin) is a terminal,
+and as lua - otherwise.
+
+
+
+When called without the option -E,
+the interpreter checks for an environment variable LUA_INIT_5_4
+(or LUA_INIT if the versioned name is not defined)
+before running any argument.
+If the variable content has the format @filename,
+then lua executes the file.
+Otherwise, lua executes the string itself.
+
+
+
+When called with the option -E,
+Lua does not consult any environment variables.
+In particular,
+the values of package.path and package.cpath
+are set with the default paths defined in luaconf.h.
+To signal to the libraries that this option is on,
+the stand-alone interpreter sets the field
+"LUA_NOENV" in the registry to a true value.
+Other libraries may consult this field for the same purpose.
+
+
+
+The options -e, -l, and -W are handled in
+the order they appear.
+For instance, an invocation like
+
+
+ $ lua -e 'a=1' -llib1 script.lua +
+will first set a to 1, then require the library lib1,
+and finally run the file script.lua with no arguments.
+(Here $ is the shell prompt. Your prompt may be different.)
+
+
+
+Before running any code,
+lua collects all command-line arguments
+in a global table called arg.
+The script name goes to index 0,
+the first argument after the script name goes to index 1,
+and so on.
+Any arguments before the script name
+(that is, the interpreter name plus its options)
+go to negative indices.
+For instance, in the call
+
+
+ $ lua -la b.lua t1 t2 +
+the table is like this: + +
+ arg = { [-2] = "lua", [-1] = "-la",
+ [0] = "b.lua",
+ [1] = "t1", [2] = "t2" }
++If there is no script in the call, +the interpreter name goes to index 0, +followed by the other arguments. +For instance, the call + +
+ $ lua -e "print(arg[1])" +
+will print "-e".
+If there is a script,
+the script is called with arguments
+arg[1], ···, arg[#arg].
+Like all chunks in Lua,
+the script is compiled as a variadic function.
+
+
+
+In interactive mode, +Lua repeatedly prompts and waits for a line. +After reading a line, +Lua first try to interpret the line as an expression. +If it succeeds, it prints its value. +Otherwise, it interprets the line as a statement. +If you write an incomplete statement, +the interpreter waits for its completion +by issuing a different prompt. + + +
+If the global variable _PROMPT contains a string,
+then its value is used as the prompt.
+Similarly, if the global variable _PROMPT2 contains a string,
+its value is used as the secondary prompt
+(issued during incomplete statements).
+
+
+
+In case of unprotected errors in the script,
+the interpreter reports the error to the standard error stream.
+If the error object is not a string but
+has a metamethod __tostring,
+the interpreter calls this metamethod to produce the final message.
+Otherwise, the interpreter converts the error object to a string
+and adds a stack traceback to it.
+When warnings are on,
+they are simply printed in the standard error output.
+
+
+
+When finishing normally,
+the interpreter closes its main Lua state
+(see lua_close).
+The script can avoid this step by
+calling os.exit to terminate.
+
+
+
+To allow the use of Lua as a
+script interpreter in Unix systems,
+Lua skips the first line of a file chunk if it starts with #.
+Therefore, Lua scripts can be made into executable programs
+by using chmod +x and the #! form,
+as in
+
+
+ #!/usr/local/bin/lua +
+Of course,
+the location of the Lua interpreter may be different in your machine.
+If lua is in your PATH,
+then
+
+
+ #!/usr/bin/env lua +
+is a more portable solution. + + + +
+Here we list the incompatibilities that you may find when moving a program +from Lua 5.3 to Lua 5.4. + + +
+You can avoid some incompatibilities by compiling Lua with
+appropriate options (see file luaconf.h).
+However,
+all these compatibility options will be removed in the future.
+More often than not,
+compatibility issues arise when these compatibility options
+are removed.
+So, whenever you have the chance,
+you should try to test your code with a version of Lua compiled
+with all compatibility options turned off.
+That will ease transitions to newer versions of Lua.
+
+
+
+Lua versions can always change the C API in ways that +do not imply source-code changes in a program, +such as the numeric values for constants +or the implementation of functions as macros. +Therefore, +you should never assume that binaries are compatible between +different Lua versions. +Always recompile clients of the Lua API when +using a new version. + + +
+Similarly, Lua versions can always change the internal representation +of precompiled chunks; +precompiled chunks are not compatible between different Lua versions. + + +
+The standard paths in the official distribution may +change between versions. + + + + + +
"1" + "2" now is an integer,
+not a float.
+__lt metamethod to emulate __le
+has been removed.
+When needed, this metamethod must be explicitly defined.
+__gc metamethods that are not functions.
+Any value will be called, if present.
+(Non-callable values will generate a warning,
+like any other error when calling a finalizer.)
+print does not call tostring
+to format its arguments;
+instead, it has this functionality hardwired.
+You should use __tostring to modify how values are printed.
+math.random
+now starts with a somewhat random seed.
+Moreover, it uses a different algorithm.
+utf8 library
+do not accept surrogates as valid code points.
+An extra parameter in these functions makes them more permissive.
+setpause" and "setstepmul"
+of the function collectgarbage are deprecated.
+You should use the new option "incremental" to set them.
+io.lines now returns four values,
+instead of just one.
+That can be a problem when it is used as the sole
+argument to another function that has optional parameters,
+such as in load(io.lines(filename, "L")).
+To fix that issue,
+you can wrap the call into parentheses,
+to adjust its number of results to one.
+lua_newuserdata,
+lua_setuservalue, and lua_getuservalue were
+replaced by lua_newuserdatauv,
+lua_setiuservalue, and lua_getiuservalue,
+which have an extra argument.
+
+
++For compatibility, the old names still work as macros assuming +one single user value. +Note, however, that userdata with zero user values +are more efficient memory-wise. +
lua_resume has an extra parameter.
+This out parameter returns the number of values on
+the top of the stack that were yielded or returned by the coroutine.
+(In previous versions,
+those values were the entire stack.)
+lua_version returns the version number,
+instead of an address of the version number.
+The Lua core should work correctly with libraries using their
+own static copies of the same core,
+so there is no need to check whether they are using the same
+address space.
+LUA_ERRGCMM was removed.
+Errors in finalizers are never propagated;
+instead, they generate a warning.
+LUA_GCSETPAUSE and LUA_GCSETSTEPMUL
+of the function lua_gc are deprecated.
+You should use the new option LUA_GCINC to set them.
++Here is the complete syntax of Lua in extended BNF. +As usual in extended BNF, +{A} means 0 or more As, +and [A] means an optional A. +(For operator precedences, see §3.4.8; +for a description of the terminals +Name, Numeral, +and LiteralString, see §3.1.) + + + + +
+
+ chunk ::= block
+
+ block ::= {stat} [retstat]
+
+ stat ::= ‘;’ |
+ varlist ‘=’ explist |
+ functioncall |
+ label |
+ break |
+ goto Name |
+ do block end |
+ while exp do block end |
+ repeat block until exp |
+ if exp then block {elseif exp then block} [else block] end |
+ for Name ‘=’ exp ‘,’ exp [‘,’ exp] do block end |
+ for namelist in explist do block end |
+ function funcname funcbody |
+ local function Name funcbody |
+ local attnamelist [‘=’ explist]
+
+ attnamelist ::= Name attrib {‘,’ Name attrib}
+
+ attrib ::= [‘<’ Name ‘>’]
+
+ retstat ::= return [explist] [‘;’]
+
+ label ::= ‘::’ Name ‘::’
+
+ funcname ::= Name {‘.’ Name} [‘:’ Name]
+
+ varlist ::= var {‘,’ var}
+
+ var ::= Name | prefixexp ‘[’ exp ‘]’ | prefixexp ‘.’ Name
+
+ namelist ::= Name {‘,’ Name}
+
+ explist ::= exp {‘,’ exp}
+
+ exp ::= nil | false | true | Numeral | LiteralString | ‘...’ | functiondef |
+ prefixexp | tableconstructor | exp binop exp | unop exp
+
+ prefixexp ::= var | functioncall | ‘(’ exp ‘)’
+
+ functioncall ::= prefixexp args | prefixexp ‘:’ Name args
+
+ args ::= ‘(’ [explist] ‘)’ | tableconstructor | LiteralString
+
+ functiondef ::= function funcbody
+
+ funcbody ::= ‘(’ [parlist] ‘)’ block end
+
+ parlist ::= namelist [‘,’ ‘...’] | ‘...’
+
+ tableconstructor ::= ‘{’ [fieldlist] ‘}’
+
+ fieldlist ::= field {fieldsep field} [fieldsep]
+
+ field ::= ‘[’ exp ‘]’ ‘=’ exp | Name ‘=’ exp | exp
+
+ fieldsep ::= ‘,’ | ‘;’
+
+ binop ::= ‘+’ | ‘-’ | ‘*’ | ‘/’ | ‘//’ | ‘^’ | ‘%’ |
+ ‘&’ | ‘~’ | ‘|’ | ‘>>’ | ‘<<’ | ‘..’ |
+ ‘<’ | ‘<=’ | ‘>’ | ‘>=’ | ‘==’ | ‘~=’ |
+ and | or
+
+ unop ::= ‘-’ | not | ‘#’ | ‘~’
+
+
+
++ + + + + + +
+ + + + diff --git a/vendor/lua-5.4.8/doc/readme.html b/vendor/lua-5.4.8/doc/readme.html new file mode 100644 index 0000000000000000000000000000000000000000..a4eb59dd38c65a64fdcfc2903e65147a8063e3f7 --- /dev/null +++ b/vendor/lua-5.4.8/doc/readme.html @@ -0,0 +1,339 @@ + + + +
+Welcome to Lua 5.4
++Lua is a powerful, efficient, lightweight, embeddable scripting language +developed by a +team +at +PUC-Rio, +the Pontifical Catholic University of Rio de Janeiro in Brazil. +Lua is +free software +used in +many products and projects +around the world. + +
+Lua's +official website +provides complete information +about Lua, +including +an +executive summary, +tips on +getting started, +and +updated +documentation, +especially the +reference manual, +which may differ slightly from the +local copy +distributed in this package. + +
+Lua is distributed in +source +form. +You need to build it before using it. +Building Lua should be straightforward +because +Lua is implemented in pure ANSI C and compiles unmodified in all known +platforms that have an ANSI C compiler. +Lua also compiles unmodified as C++. +The instructions given below for building Lua are for Unix-like platforms, +such as Linux and macOS. +See also +instructions for other systems +and +customization options. + +
+If you don't have the time or the inclination to compile Lua yourself, +get a binary from +LuaBinaries. + +
+In most common Unix-like platforms, simply do "make". +Here are the details. + +
+
+
+
+ guess aix bsd c89 freebsd generic ios linux linux-readline macosx mingw posix solaris +
++ If your platform is listed, just do "make xxx", where xxx + is your platform name. +
+ If your platform is not listed, try the closest one or posix, generic, + c89, in this order. +
+
+
+If you're running Linux, try "make linux-readline" to build the interactive Lua interpreter with handy line-editing and history capabilities. +If you get compilation errors, +make sure you have installed the readline development package +(which is probably named libreadline-dev or readline-devel). +If you get link errors after that, +then try "make linux-readline MYLIBS=-ltermcap". + +
+ Once you have built Lua, you may want to install it in an official + place in your system. In this case, do "make install". The official + place and the way to install files are defined in the Makefile. You'll + probably need the right permissions to install files, and so may need to do "sudo make install". + +
+ To build and install Lua in one step, do "make all install", + or "make xxx install", + where xxx is your platform name. + +
+ To install Lua locally after building it, do "make local". + This will create a directory install with subdirectories + bin, include, lib, man, share, + and install Lua as listed below. + + To install Lua locally, but in some other directory, do + "make install INSTALL_TOP=xxx", where xxx is your chosen directory. + The installation starts in the src and doc directories, + so take care if INSTALL_TOP is not an absolute path. + +
+ These are the only directories you need for development. + If you only want to run Lua programs, + you only need the files in bin and man. + The files in include and lib are needed for + embedding Lua in C or C++ programs. + +
+ Three kinds of things can be customized by editing a file: +
+ You don't actually need to edit the Makefiles because you may set the + relevant variables in the command line when invoking make. + Nevertheless, it's probably best to edit and save the Makefiles to + record the changes you've made. + +
+ On the other hand, if you need to customize some Lua features, + edit src/luaconf.h before building and installing Lua. + The edited file will be the one installed, and + it will be used by any Lua clients that you build, to ensure consistency. + Further customization is available to experts by editing the Lua sources. + +
+ If you're not using the usual Unix tools, then the instructions for + building Lua depend on the compiler you use. You'll need to create + projects (or whatever your compiler uses) for building the library, + the interpreter, and the compiler, as follows: + +
+ To use Lua as a library in your own programs, you need to know how to + create and use libraries with your compiler. Moreover, to dynamically load + C libraries for Lua, you'll need to know how to create dynamic libraries + and you'll need to make sure that the Lua API functions are accessible to + those dynamic libraries — but don't link the Lua library + into each dynamic library. For Unix, we recommend that the Lua library + be linked statically into the host program and its symbols exported for + dynamic linking; src/Makefile does this for the Lua interpreter. + For Windows, we recommend that the Lua library be a DLL. + In all cases, the compiler luac should be linked statically. + +
+ As mentioned above, you may edit src/luaconf.h to customize + some features before building Lua. + +
+Here are the main changes introduced in Lua 5.4. +The +reference manual +lists the +incompatibilities that had to be introduced. + +
+
+![[Open Source Initiative Approved License]](OSIApproved_100X125.png)
+
+Lua is free software distributed under the terms of the
+MIT license
+reproduced below;
+it may be used for any purpose, including commercial purposes,
+at absolutely no cost without having to ask us.
+
+The only requirement is that if you do use Lua,
+then you should give us credit by including the appropriate copyright notice somewhere in your product or its documentation.
+
+For details, see the
+license page.
+
+
+Copyright © 1994–2025 Lua.org, PUC-Rio. + +++Permission is hereby granted, free of charge, to any person obtaining a copy +of this software and associated documentation files (the "Software"), to deal +in the Software without restriction, including without limitation the rights +to use, copy, modify, merge, publish, distribute, sublicense, and/or sell +copies of the Software, and to permit persons to whom the Software is +furnished to do so, subject to the following conditions: + +
+The above copyright notice and this permission notice shall be included in +all copies or substantial portions of the Software. + +
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