+Lua 5.2 Reference Manual
+
+Lua 5.2 Reference Manual
++ +Copyright © 2011–2013 Lua.org, PUC-Rio. +Freely available under the terms of the +Lua license. + +
+ + + + + + +
+Lua is an extension programming language designed to support +general procedural programming with data description +facilities. +It also offers good support for object-oriented programming, +functional programming, and data-driven programming. +Lua is intended to be used as a powerful, lightweight, +embeddable scripting language for any program that needs one. +Lua is implemented as a library, written in clean C, +the common subset of Standard C and C++. + + +
+Being an extension language, Lua has no notion of a "main" program:
+it only works embedded in a host client,
+called the embedding program or simply the host.
+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.
+The Lua distribution includes a sample host program called lua,
+which uses the Lua library to offer a complete, standalone Lua interpreter,
+for interactive or batch use.
+
+
+
+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.
+Nil is the type of the value nil,
+whose main property is to be different from any other value;
+it usually represents the absence of a useful value.
+Boolean is the type of the values false and true.
+Both nil and false make a condition false;
+any other value makes it true.
+Number represents real (double-precision floating-point) numbers.
+Operations on numbers follow the same rules of
+the underlying C implementation,
+which, in turn, usually follows the IEEE 754 standard.
+(It is easy to build Lua interpreters that use other
+internal representations for numbers,
+such as single-precision floats or long integers;
+see file luaconf.h.)
+String represents immutable sequences of bytes.
+
+Lua is 8-bit clean:
+strings can contain any 8-bit value,
+including embedded zeros ('\0').
+
+
+
+Lua can call (and manipulate) functions written in Lua and +functions written in C +(see §3.4.9). + + +
+The type userdata is provided to allow arbitrary C data to +be stored in Lua variables. +A userdata value is a pointer to a block of raw memory. +There are two kinds of userdata: +full userdata, where the block of memory is managed by Lua, +and light userdata, where the block of memory is managed by the host. +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. + + +
+The type thread represents independent threads of execution +and it is used to implement coroutines (see §2.6). +Do not confuse Lua threads with operating-system threads. +Lua supports coroutines on all systems, +even those that do not support threads. + + +
+The type table implements associative arrays,
+that is, arrays that can be indexed not only with numbers,
+but with any Lua value except nil and NaN
+(Not a Number, a special numeric value used to represent
+undefined or unrepresentable results, such as 0/0).
+Tables can be heterogeneous;
+that is, they can contain values of all types (except nil).
+Any key with 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, sequences,
+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 §3.4.8).
+
+
+
+We use the term sequence to denote a table where +the set of all positive numeric keys is equal to {1..n} +for some integer n, +which is called the length of the sequence (see §3.4.6). + + +
+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 §3.4.10). + + +
+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).
+
+
+
+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 §6.1).
+
+
+
+
+
+
+As will be discussed in §3.2 and §3.3.3,
+any reference to a global name var is syntactically translated
+to _ENV.var.
+Moreover, every chunk is compiled in the scope of
+an external local variable called _ENV (see §3.3.2),
+so _ENV itself is never a global name in a chunk.
+
+
+
+Despite the existence of this external _ENV variable and
+the translation of global names,
+_ENV is a completely regular name.
+In particular,
+you can define new variables and parameters with that name.
+Each reference to a global 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 §4.5).
+In Lua, the variable _G is initialized with this same value.
+
+
+
+When Lua compiles a chunk,
+it initializes the value of its _ENV upvalue
+with the global environment (see load).
+Therefore, by default,
+global variables in Lua code refer to entries in the global environment.
+Moreover, all standard libraries are loaded in the global environment
+and several 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.)
+
+
+
+If you change the global environment in the registry
+(through C code or the debug library),
+all chunks loaded after the change will get the new environment.
+Previously loaded chunks are not affected, however,
+as each has its own reference to the environment in its _ENV variable.
+Moreover, the variable _G
+(which is stored in the original global environment)
+is never updated by Lua.
+
+
+
+
+
+
+Because Lua is an embedded extension language,
+all Lua actions start from C code in the host program
+calling a function from the Lua library (see lua_pcall).
+Whenever an 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).
+
+
+
+Lua code can explicitly generate an error by calling the
+error function.
+If you need to catch errors in Lua,
+you can use pcall or xpcall
+to call a given function in protected mode.
+
+
+
+Whenever there is an error, +an error object (also called an error message) +is propagated with information about the error. +Lua itself only generates errors where the error object is a string, +but programs may generate errors with +any value for the error object. + + +
+When you use xpcall or lua_pcall,
+you may give a message handler
+to be called in case of errors.
+This function is called with the original error message
+and returns a new error message.
+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, Lua breaks it and returns an appropriate message.
+
+
+
+
+
+
+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 special operations.
+You can change several aspects of the behavior
+of operations over 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 keys in a metatable are derived from the event names;
+the corresponding values are called metamethods.
+In the previous example, the event is "add"
+and the metamethod is the function that performs the addition.
+
+
+
+You can query the metatable of any value
+using the getmetatable function.
+
+
+
+You can replace the metatable of tables
+using the setmetatable function.
+You cannot change the metatable of other types from Lua
+(except by using the debug library);
+you must use the C API for that.
+
+
+
+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 metatable controls how an object behaves in arithmetic operations, +order comparisons, concatenation, length operation, and indexing. +A metatable also can define a function to be called +when a userdata or a table is garbage collected. +When Lua performs one of these operations over a value, +it checks whether this value has a metatable with the corresponding event. +If so, the value associated with that key (the metamethod) +controls how Lua will perform the operation. + + +
+Metatables control the operations listed next.
+Each operation is identified by its corresponding name.
+The key for each operation is a string with its name prefixed by
+two underscores, '__';
+for instance, the key for operation "add" is the
+string "__add".
+
+
+
+The semantics of these operations is better explained by a Lua function
+describing how the interpreter executes the operation.
+The code shown here in Lua is only illustrative;
+the real behavior is hard coded in the interpreter
+and it is much more efficient than this simulation.
+All functions used in these descriptions
+(rawget, tonumber, etc.)
+are described in §6.1.
+In particular, to retrieve the metamethod of a given object,
+we use the expression
+
+
+ metatable(obj)[event] +
+This should be read as + +
+ rawget(getmetatable(obj) or {}, event)
++This means that the access to a metamethod does not invoke other metamethods, +and access to objects with no metatables does not fail +(it simply results in nil). + + +
+For the unary - and # operators,
+the metamethod is called with a dummy second argument.
+This extra argument is only to simplify Lua's internals;
+it may be removed in future versions and therefore it is not present
+in the following code.
+(For most uses this extra argument is irrelevant.)
+
+
+
+
+ operation.
+
+
+
+
+The function getbinhandler below defines how Lua chooses a handler
+for a binary operation.
+First, Lua tries the first operand.
+If its type does not define a handler for the operation,
+then Lua tries the second operand.
+
+
+ function getbinhandler (op1, op2, event) + return metatable(op1)[event] or metatable(op2)[event] + end +
+By using this function,
+the behavior of the op1 + op2 is
+
+
+ function add_event (op1, op2) + local o1, o2 = tonumber(op1), tonumber(op2) + if o1 and o2 then -- both operands are numeric? + return o1 + o2 -- '+' here is the primitive 'add' + else -- at least one of the operands is not numeric + local h = getbinhandler(op1, op2, "__add") + if h then + -- call the handler with both operands + return (h(op1, op2)) + else -- no handler available: default behavior + error(···) + end + end + end +
+
- operation.
+
+Behavior similar to the "add" operation.
+* operation.
+
+Behavior similar to the "add" operation.
+/ operation.
+
+Behavior similar to the "add" operation.
+% operation.
+
+Behavior similar to the "add" operation,
+with the operation
+o1 - floor(o1/o2)*o2 as the primitive operation.
+^ (exponentiation) operation.
+
+Behavior similar to the "add" operation,
+with the function pow (from the C math library)
+as the primitive operation.
+- operation.
+
+
++ function unm_event (op) + local o = tonumber(op) + if o then -- operand is numeric? + return -o -- '-' here is the primitive 'unm' + else -- the operand is not numeric. + -- Try to get a handler from the operand + local h = metatable(op).__unm + if h then + -- call the handler with the operand + return (h(op)) + else -- no handler available: default behavior + error(···) + end + end + end +
+
.. (concatenation) operation.
+
+
++ function concat_event (op1, op2) + if (type(op1) == "string" or type(op1) == "number") and + (type(op2) == "string" or type(op2) == "number") then + return op1 .. op2 -- primitive string concatenation + else + local h = getbinhandler(op1, op2, "__concat") + if h then + return (h(op1, op2)) + else + error(···) + end + end + end +
+
# operation.
+
+
++ function len_event (op) + if type(op) == "string" then + return strlen(op) -- primitive string length + else + local h = metatable(op).__len + if h then + return (h(op)) -- call handler with the operand + elseif type(op) == "table" then + return #op -- primitive table length + else -- no handler available: error + error(···) + end + end + end +
+See §3.4.6 for a description of the length of a table. +
== operation.
+
+The function getequalhandler defines how Lua chooses a metamethod
+for equality.
+A metamethod is selected only when both values
+being compared have the same type
+and the same metamethod for the selected operation,
+and the values are either tables or full userdata.
+
++ function getequalhandler (op1, op2) + if type(op1) ~= type(op2) or + (type(op1) ~= "table" and type(op1) ~= "userdata") then + return nil -- different values + end + local mm1 = metatable(op1).__eq + local mm2 = metatable(op2).__eq + if mm1 == mm2 then return mm1 else return nil end + end +
+The "eq" event is defined as follows: + +
+ function eq_event (op1, op2) + if op1 == op2 then -- primitive equal? + return true -- values are equal + end + -- try metamethod + local h = getequalhandler(op1, op2) + if h then + return not not h(op1, op2) + else + return false + end + end +
+Note that the result is always a boolean. +
< operation.
+
+
++ function lt_event (op1, op2) + if type(op1) == "number" and type(op2) == "number" then + return op1 < op2 -- numeric comparison + elseif type(op1) == "string" and type(op2) == "string" then + return op1 < op2 -- lexicographic comparison + else + local h = getbinhandler(op1, op2, "__lt") + if h then + return not not h(op1, op2) + else + error(···) + end + end + end +
+Note that the result is always a boolean. +
<= operation.
+
+
++ function le_event (op1, op2) + if type(op1) == "number" and type(op2) == "number" then + return op1 <= op2 -- numeric comparison + elseif type(op1) == "string" and type(op2) == "string" then + return op1 <= op2 -- lexicographic comparison + else + local h = getbinhandler(op1, op2, "__le") + if h then + return not not h(op1, op2) + else + h = getbinhandler(op1, op2, "__lt") + if h then + return not h(op2, op1) + else + error(···) + end + end + end + end +
+Note that, in the absence of a "le" metamethod,
+Lua tries the "lt", assuming that a <= b is
+equivalent to not (b < a).
+
+
+
+As with the other comparison operators, +the result is always a boolean. +
table[key].
+Note that the metamethod is tried only
+when key is not present in table.
+(When table is not a table,
+no key is ever present,
+so the metamethod is always tried.)
+
+
++ function gettable_event (table, key) + local h + if type(table) == "table" then + local v = rawget(table, key) + -- if key is present, return raw value + if v ~= nil then return v end + h = metatable(table).__index + if h == nil then return nil end + else + h = metatable(table).__index + if h == nil then + error(···) + end + end + if type(h) == "function" then + return (h(table, key)) -- call the handler + else return h[key] -- or repeat operation on it + end + end +
+
table[key] = value.
+Note that the metamethod is tried only
+when key is not present in table.
+
+
++ function settable_event (table, key, value) + local h + if type(table) == "table" then + local v = rawget(table, key) + -- if key is present, do raw assignment + if v ~= nil then rawset(table, key, value); return end + h = metatable(table).__newindex + if h == nil then rawset(table, key, value); return end + else + h = metatable(table).__newindex + if h == nil then + error(···) + end + end + if type(h) == "function" then + h(table, key,value) -- call the handler + else h[key] = value -- or repeat operation on it + end + end +
+
+ function function_event (func, ...) + if type(func) == "function" then + return func(...) -- primitive call + else + local h = metatable(func).__call + if h then + return h(func, ...) + else + error(···) + end + end + end +
+
+Lua performs automatic memory management. +This means that +you have to worry neither about allocating memory for new objects +nor about freeing it when the objects are no longer needed. +Lua manages memory automatically by running +a garbage collector to collect all dead objects +(that is, objects that are no longer accessible from Lua). +All memory used by Lua is subject to automatic management: +strings, tables, userdata, functions, threads, internal structures, etc. + + +
+Lua implements an incremental mark-and-sweep collector. +It uses two numbers to control its garbage-collection cycles: +the garbage-collector pause and +the garbage-collector step multiplier. +Both use percentage points as units +(e.g., a value of 100 means an internal value of 1). + + +
+The garbage-collector pause +controls how long the collector waits before starting a new cycle. +Larger values make the collector less aggressive. +Values smaller 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 garbage-collector step multiplier +controls the relative speed of the collector relative to +memory allocation. +Larger values make the collector more aggressive but also increase +the size of each incremental step. +Values smaller than 100 make the collector too slow and +can result in the collector never finishing a cycle. +The default is 200, +which means that the collector runs at "twice" +the speed of memory allocation. + + +
+If you set the step multiplier to a very large number +(larger than 10% of the maximum number of +bytes that the program may use), +the collector behaves like a stop-the-world collector. +If you then set the pause to 200, +the collector behaves as in old Lua versions, +doing a complete collection every time Lua doubles its +memory usage. + + +
+You can change these numbers by calling lua_gc in C
+or collectgarbage in Lua.
+You can also use these functions to control
+the collector directly (e.g., stop and restart it).
+
+
+
+As an experimental feature in Lua 5.2, +you can change the collector's operation mode +from incremental to generational. +A generational collector assumes that most objects die young, +and therefore it traverses only young (recently created) objects. +This behavior can reduce the time used by the collector, +but also increases memory usage (as old dead objects may accumulate). +To mitigate this second problem, +from time to time the generational collector performs a full collection. +Remember that this is an experimental feature; +you are welcome to try it, +but check your gains. + + + +
+You can set garbage-collector metamethods for tables +and, using the C API, +for full userdata (see §2.4). +These metamethods are also called finalizers. +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 field indexed by the string "__gc".
+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.
+However, after an object is marked,
+you can freely change the __gc field of its metatable.
+
+
+
+When a marked object becomes garbage, +it is not collected immediately by the garbage collector. +Instead, Lua puts it in a list. +After the collection, +Lua does the equivalent of the following function +for each object in that list: + +
+ function gc_event (obj) + local h = metatable(obj).__gc + if type(h) == "function" then + h(obj) + end + end ++ +
+At the end of each garbage-collection cycle, +the finalizers for objects are called in +the reverse order that they were marked for collection, +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, +it (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 there is a permanent resurrection. +In any case, +the object memory is freed only when it becomes completely inaccessible; +its finalizer will never be called twice. + + +
+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 new objects for collection during that phase,
+these new objects will not be finalized.
+
+
+
+
+
+
+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 keys allows the collection of its keys,
+but prevents the collection of its values.
+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.
+If the __mode field is a string containing the character 'k',
+the keys in the table are weak.
+If __mode contains 'v',
+the values in the table are weak.
+
+
+
+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 its associated value is collected). +Although strings are subject to garbage collection, +they do not have an explicit construction, +and therefore 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,
+at the first line of its main function.
+Extra arguments passed to coroutine.resume are passed on
+to the coroutine main 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 the first case, coroutine.resume returns true,
+plus any values returned by the coroutine main function.
+In case of errors, coroutine.resume returns false
+plus an error message.
+
+
+
+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,
+coroutine.wrap does not catch errors;
+any error is propagated to the caller.
+
+
+
+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 (including new lines) and comments +between lexical elements (tokens), +except as delimiters between names and keywords. + + +
+Names +(also called identifiers) +in Lua can be any string of letters, +digits, and underscores, +not beginning with a digit. +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, names starting with an underscore followed by
+uppercase letters (such as _VERSION)
+are reserved for variables used by Lua.
+
+
+
+The following strings denote other tokens: + +
+ + - * / % ^ #
+ == ~= <= >= < > =
+ ( ) { } [ ] ::
+ ; : , . .. ...
+
+
+
+Literal strings
+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 real newline
+results in a newline in the string.
+The escape sequence '\z' skips the following span
+of white-space 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 byte in a literal string can also be specified by its numerical 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 is to be followed by a digit,
+it must be expressed using exactly three digits.)
+Strings in Lua can contain any 8-bit value, including embedded zeros,
+which can be specified as '\0'.
+
+
+
+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 proper 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.
+
+
+
+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 file functions may have problems with +some control characters. +So, it is safer to represent +non-text data as a quoted literal with +explicit escape sequences for non-text characters. + + +
+For convenience,
+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"]==] ++ +
+A numerical constant 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'.
+Examples of valid numerical constants are
+
+
+ 3 3.0 3.1416 314.16e-2 0.31416E1 + 0xff 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.
+Long comments are frequently used to disable code temporarily.
+
+
+
+
+
+
+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, as defined in §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.
+An access to an indexed variable t[i] is equivalent to
+a call gettable_event(t,i).
+(See §2.4 for a complete description of the
+gettable_event function.
+This function is not defined or callable in Lua.
+We use it here only for explanatory purposes.)
+
+
+
+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,
+_ENV is never a global name (see §2.2).
+
+
+
+
+
+
+Lua supports an almost conventional set of statements, +similar to those in Pascal or C. +This set includes +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 ::= ‘;’ ++ +
+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 it 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 §3.4.10).
+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 upvalue,
+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 precompiles the chunk into instructions for a virtual machine, +and then it executes the compiled code +with an interpreter for the virtual machine. + + +
+Chunks can also be precompiled into binary form;
+see program luac for details.
+Programs in source and compiled forms are interchangeable;
+Lua automatically detects the file type and acts accordingly.
+
+
+
+
+
+
+
+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. +If there are more values than needed, +the excess values are thrown away. +If there are fewer values than needed, +the list is extended with as many nil's as needed. +If the list of expressions ends with a function call, +then all values returned by that call enter the list of values, +before the adjustment +(except when the call is enclosed in parentheses; see §3.4). + + +
+The assignment statement first evaluates all its expressions +and only then are the assignments performed. +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.
+
+
+
+The meaning of assignments to global variables
+and table fields can be changed via metatables.
+An assignment to an indexed variable t[i] = val is equivalent to
+settable_event(t,i,val).
+(See §2.4 for a complete description of the
+settable_event function.
+This function is not defined or callable in Lua.
+We use it here only for explanatory purposes.)
+
+
+
+An assignment to a global variable x = val
+is equivalent to the assignment
+_ENV.x = val (see §2.2).
+
+
+
+
+
+
+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 are considered false. +All values different from nil and false are considered true +(in particular, the number 0 and the empty string are also 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 blocks where a label with the same name is defined and +inside nested functions. +A goto may jump to any visible label as long as it does not +enter into the scope of a local variable. + + +
+Labels and empty statements are called void statements, +as they perform no actions. + + +
+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 a function in disguise). + +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 really 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 numeric and one generic. + + +
+The numeric for loop repeats a block of code while a +control variable runs through an arithmetic progression. +It has the following syntax: + +
+ stat ::= for Name ‘=’ exp ‘,’ exp [‘,’ exp] do block end +
+The block is repeated for name starting at the value of +the first exp, until it passes the second exp by steps of the +third exp. +More precisely, a for statement like + +
+ for v = e1, e2, e3 do block end +
+is equivalent to the code: + +
+ do + local var, limit, step = tonumber(e1), tonumber(e2), tonumber(e3) + if not (var and limit and step) then error() end + while (step > 0 and var <= limit) or (step <= 0 and var >= limit) do + local v = var + block + var = var + step + end + end +
+Note the following: + +
var, limit, and step are invisible variables.
+The names shown here are for explanatory purposes only.
+v is local to the loop;
+you cannot use its value after the for ends or is broken.
+If you need this value,
+assign it to another variable before breaking or 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 block end +
+is equivalent to the code: + +
+ do + local f, s, var = explist + while true do + local var_1, ···, var_n = f(s, var) + if var_1 == nil then break end + var = var_1 + block + end + end +
+Note the following: + +
explist is evaluated only once.
+Its results are an iterator function,
+a state,
+and an initial value for the first iterator variable.
+f, s, and var are invisible variables.
+The names are here for explanatory purposes only.
+var_i are local to the loop;
+you cannot use their values after the for ends.
+If you need these values,
+then assign them to other variables before breaking or exiting 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 §3.4.9. + + + + + +
+Local variables can be declared anywhere inside a block. +The declaration can include an initial assignment: + +
+ stat ::= local namelist [‘=’ explist] +
+If present, an initial assignment has the same semantics +of a multiple assignment (see §3.3.3). +Otherwise, all variables are initialized with nil. + + +
+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. + + + + + + + +
+The basic expressions in Lua are the following: + +
+ exp ::= prefixexp + exp ::= nil | false | true + exp ::= Number + exp ::= String + exp ::= functiondef + exp ::= tableconstructor + exp ::= ‘...’ + exp ::= exp binop exp + exp ::= unop exp + prefixexp ::= var | functioncall | ‘(’ exp ‘)’ ++ +
+Numbers and literal strings are explained in §3.1;
+variables are explained in §3.2;
+function definitions are explained in §3.4.10;
+function calls are explained in §3.4.9;
+table constructors are explained in §3.4.8.
+Vararg expressions,
+denoted by three dots ('...'), can only be used when
+directly inside a vararg function;
+they are explained in §3.4.10.
+
+
+
+Binary operators comprise arithmetic operators (see §3.4.1), +relational operators (see §3.4.3), logical operators (see §3.4.4), +and the concatenation operator (see §3.4.5). +Unary operators comprise the unary minus (see §3.4.1), +the unary not (see §3.4.4), +and the unary length operator (see §3.4.6). + + +
+Both function calls and vararg expressions can result in multiple values. +If a function call is used as a statement (see §3.3.6), +then its return list is adjusted to zero elements, +thus discarding all returned values. +If an expression is used as the last (or the only) element +of a list of expressions, +then no adjustment is made +(unless the expression is enclosed in parentheses). +In all other contexts, +Lua adjusts the result list to one element, +either discarding all values except the first one +or adding a single nil if there are no values. + + +
+Here are some examples: + +
+ f() -- adjusted to 0 results
+ g(f(), x) -- f() is adjusted to 1 result
+ g(x, f()) -- g gets x plus all results from f()
+ a,b,c = f(), x -- f() is adjusted to 1 result (c gets nil)
+ a,b = ... -- a gets the first vararg parameter, b gets
+ -- the second (both a and b can get nil if there
+ -- is no corresponding vararg parameter)
+
+ a,b,c = x, f() -- f() is adjusted to 2 results
+ a,b,c = f() -- f() is adjusted to 3 results
+ return f() -- returns all results from f()
+ return ... -- returns all received vararg parameters
+ 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 parameters
+ {f(), nil} -- f() is adjusted to 1 result
+
+
+
+Any expression enclosed in parentheses always results in only one value.
+Thus,
+(f(x,y,z)) is always a single value,
+even if f returns several values.
+(The value of (f(x,y,z)) is the first value returned by f
+or nil if f does not return any values.)
+
+
+
+
+Lua supports the usual arithmetic operators:
+the binary + (addition),
+- (subtraction), * (multiplication),
+/ (division), % (modulo), and ^ (exponentiation);
+and unary - (mathematical negation).
+If the operands are numbers, or strings that can be converted to
+numbers (see §3.4.2),
+then all operations have the usual meaning.
+Exponentiation works for any exponent.
+For instance, x^(-0.5) computes the inverse of the square root of x.
+Modulo is defined as
+
+
+ a % b == a - math.floor(a/b)*b +
+That is, it is the remainder of a division that rounds +the quotient towards minus infinity. + + + + + +
+Lua provides automatic conversion between
+string and number values at run time.
+Any arithmetic operation applied to a string tries to convert
+this string to a number, following the rules of the Lua lexer.
+(The string may have leading and trailing spaces and a sign.)
+Conversely, whenever a number is used where a string is expected,
+the number is converted to a string, in a reasonable format.
+For complete control over how numbers are converted to strings,
+use the format function from the string library
+(see string.format).
+
+
+
+
+
+
+The relational operators in Lua are + +
+ == ~= < > <= >= +
+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.
+Numbers and strings are compared in the usual way.
+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, userdata, or thread),
+this new object is different from any previously existing object.
+Closures with the same reference are always equal.
+Closures with any detectable difference
+(different behavior, different definition) are always different.
+
+
+
+You can change the way that Lua compares tables and userdata +by using the "eq" metamethod (see §2.4). + + +
+The conversion rules of §3.4.2
+do not apply to equality comparisons.
+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 as such.
+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.
+
+
+
+
+
+
+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-cut 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 +
+(In this manual,
+--> indicates the result of the preceding expression.)
+
+
+
+
+
+
+The string concatenation operator in Lua is
+denoted by two dots ('..').
+If both operands are strings or numbers, then they are converted to
+strings according to the rules mentioned in §3.4.2.
+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).
+
+
+
+A program can modify the behavior of the length operator for
+any value but strings through the __len metamethod (see §2.4).
+
+
+
+Unless a __len metamethod is given,
+the length of a table t is only defined if the
+table is a sequence,
+that is,
+the set of its positive numeric keys is equal to {1..n}
+for some integer n.
+In that case, n is its length.
+Note that a table like
+
+
+ {10, 20, nil, 40}
+
+is not a sequence, because it has the key 4
+but does not have the key 3.
+(So, there is no n such that the set {1..n} is equal
+to the set of positive numeric keys of that table.)
+Note, however, that non-numeric keys do not interfere
+with whether a table is a sequence.
+
+
+
+
+
+
+Operator precedence in Lua follows the table below, +from lower to higher priority: + +
+ or + and + < > <= >= ~= == + .. + + - + * / % + not # - (unary) + ^ +
+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.
+Finally, fields of the form exp are equivalent to
+[i] = exp, where i are consecutive numerical 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
+
+
+
+If the last field in the list has the form exp
+and the expression is a function call or a vararg expression,
+then all values returned by this expression enter the list consecutively
+(see §3.4.9).
+
+
+
+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, the prefixexp "call" metamethod is called, +having as first parameter the value of prefixexp, +followed by the original call arguments +(see §2.4). + + +
+The form + +
+ functioncall ::= prefixexp ‘:’ Name args +
+can be used to call "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 ::= String +
+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 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;
+this syntax makes the calling function return exactly
+the returns of the called function.
+So, none of the following examples are tail calls:
+
+
+ return (f(x)) -- results adjusted to 1 + return 2 * f(x) + 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. +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 function is called,
+the list of arguments is adjusted to
+the length of the list of parameters,
+unless the function is a vararg function,
+which is indicated by three dots ('...')
+at the end of its parameter list.
+A vararg 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.
+If a vararg expression is used inside another expression
+or in the middle of a list of expressions,
+then its return list is adjusted to one element.
+If the expression is used as the last element of a list of expressions,
+then no adjustment is made
+(unless that last expression is enclosed in parentheses).
+
+
+
+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 larger than 1000. + + +
+The colon syntax
+is used for defining methods,
+that is, functions that have an implicit extra parameter self.
+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 ++ + + + + + +
+ +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. +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, +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.
+
+
+
+
+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.). + + +
+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 pushes 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); +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.
+You can use the function lua_checkstack
+to ensure that the stack has extra slots when pushing new elements.
+
+
+
+Whenever Lua calls C,
+it ensures that the stack has at least LUA_MINSTACK extra slots.
+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.
+
+
+
+When you call a Lua function
+without a fixed number of results (see lua_call),
+Lua ensures that the stack has enough size for all results,
+but it does not ensure any extra space.
+So, before pushing anything in the stack after such a call
+you should use lua_checkstack.
+
+
+
+
+
+
+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
+real position within the stack, that is,
+its position lies between 1 and the stack top
+(1 ≤ abs(index) ≤ top).
+
+Usually, functions that can modify the value at an index
+require valid indices.
+
+
+
+Unless otherwise noted, +any function that accepts valid indices also accepts pseudo-indices, +which represent some Lua values that are accessible to C code +but which are not in the stack. +Pseudo-indices are used to access the registry +and the upvalues of a C function (see §4.4). + + +
+Functions that do not need a specific stack position, +but only a value in the stack (e.g., query functions), +can be called with acceptable indices. +An acceptable index can be any valid index, +including the pseudo-indices, +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.) +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 first 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.
+
+
+
+
+
+
+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 value associated with a function is at position
+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),
+produces an acceptable but invalid index.
+
+
+
+
+
+
+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 located at pseudo-index
+LUA_REGISTRYINDEX,
+which is a valid index.
+Any C library can store data into this table,
+but it should 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 global 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, +implemented by the auxiliary library, +and by some predefined values. +Therefore, integer keys should 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.
+(You can also choose to use exceptions if you compile Lua as C++;
+search for LUAI_THROW in the source code.)
+When Lua faces any error
+(such as a memory allocation error, type errors, syntax errors,
+and runtime errors)
+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.
+
+
+
+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 runs as if it were a message handler (see §2.3); +in particular, the error message is at the top of the stack. +However, there is no guarantees about stack space. +To push anything on the stack, +the panic function should first check the available space (see §4.2). + + +
+Most functions in the API can throw an error, +for instance due to a memory allocation error. +The documentation for each function indicates whether +it can throw errors. + + +
+Inside a C function you can throw an error by calling lua_error.
+
+
+
+
+
+
+Internally, Lua uses the C longjmp facility to yield a coroutine.
+Therefore, if a 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 called 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. + + +
+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.
+
+
+
+The only difference in the Lua state between the original function
+and its continuation is the result of a call to lua_getctx.
+
+
+
+
+
+
+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
+(e.g., they may depend on what is on the stack).
+The third field, x,
+tells whether the function may throw errors:
+'-' means the function never throws any error;
+'e' means the function may throw errors;
+'v' means the function may throw an error on purpose.
+
+
+
+
lua_absindex+[-0, +0, –] +
int lua_absindex (lua_State *L, int idx);+ +
+Converts the acceptable index idx into an absolute index
+(that is, one that does not depend on the stack top).
+
+
+
+
+
+
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;
+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 should behave like free
+and return NULL.
+
+
+
+When nsize is not zero,
+the allocator should behave like realloc.
+The allocator returns NULL
+if and only if it cannot fulfill the request.
+Lua assumes that the allocator never fails when
+osize >= nsize.
+
+
+
+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 Standard C ensures
+that free(NULL) has no effect and that
+realloc(NULL, size) is equivalent to malloc(size).
+This code assumes that realloc does not fail when shrinking a block.
+(Although Standard C does not ensure this behavior,
+it seems to be a safe assumption.)
+
+
+
+
+
+
lua_arith+[-(2|1), +1, e] +
void lua_arith (lua_State *L, int op);+ +
+Performs an arithmetic operation over the two values +(or one, in the case of negation) +at the top of the stack, +with the value at 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 division (/)LUA_OPMOD: performs modulo (%)LUA_OPPOW: performs exponentiation (^)LUA_OPUNM: performs mathematical negation (unary -)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 §4.6). + + + + + +
lua_call+[-(nargs+1), +nresults, e] +
void lua_call (lua_State *L, int nargs, int nresults);+ +
+Calls a function. + + +
+To call a function you must use the following protocol:
+first, the function to be called is pushed onto the stack;
+then, the arguments to the function 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.
+All arguments and the function value are popped from the stack
+when the function is called.
+The function results are pushed onto the stack when the function returns.
+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.
+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 inside the called 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_pushstring(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, int ctx, + lua_CFunction k);+ +
+This function behaves exactly like lua_call,
+but allows the called function to yield (see §4.7).
+
+
+
+
+
+
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 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 numerical arguments and returns their average and sum: + +
+ static int foo (lua_State *L) {
+ int n = lua_gettop(L); /* number of arguments */
+ lua_Number sum = 0;
+ int i;
+ for (i = 1; i <= n; i++) {
+ if (!lua_isnumber(L, i)) {
+ lua_pushstring(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 extra);+ +
+Ensures that there are at least extra free stack slots in the stack.
+It returns false if it cannot fulfill the request,
+because it would cause the stack to be larger than a fixed maximum size
+(typically at least a few thousand elements) or
+because it cannot allocate memory for the new stack size.
+This function never shrinks the stack;
+if the stack is already larger than the new size,
+it is left unchanged.
+
+
+
+
+
+
lua_close+[-0, +0, –] +
void lua_close (lua_State *L);+ +
+Destroys 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, +might need to close states as soon as they are not needed. + + + + + +
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 non 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 at 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 §3.4.5).
+
+
+
+
+
+
lua_copy+[-0, +0, –] +
void lua_copy (lua_State *L, int fromidx, int toidx);+ +
+Moves the element at index fromidx
+into the valid index toidx
+without shifting any element
+(therefore replacing the value at that position).
+
+
+
+
+
+
lua_createtable+[-0, +1, e] +
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 pre-allocation is useful for 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, e] +
int lua_dump (lua_State *L, lua_Writer writer, void *data);+ +
+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.
+
+
+
+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);+ +
+Generates a Lua error.
+The error message (which can actually be a Lua value of any type)
+must be on the stack top.
+This function does a long jump,
+and therefore never returns
+(see luaL_error).
+
+
+
+
+
+
lua_gc+[-0, +0, e] +
int lua_gc (lua_State *L, int what, int data);+ +
+Controls the garbage collector. + + +
+This function performs several tasks,
+according to the value of the parameter what:
+
+
LUA_GCSTOP:
+stops the garbage collector.
+LUA_GCRESTART:
+restarts the garbage collector.
+LUA_GCCOLLECT:
+performs a full garbage-collection cycle.
+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:
+performs an incremental step of garbage collection.
+The step "size" is controlled by data
+(larger values mean more steps) in a non-specified way.
+If you want to control the step size
+you must experimentally tune the value of data.
+The function returns 1 if the step finished a
+garbage-collection cycle.
+LUA_GCSETPAUSE:
+sets data as the new value
+for the pause of the collector (see §2.5).
+The function returns the previous value of the pause.
+LUA_GCSETSTEPMUL:
+sets data as the new value for the step multiplier of
+the collector (see §2.5).
+The function returns the previous value of the step multiplier.
+LUA_GCISRUNNING:
+returns a boolean that tells whether the collector is running
+(i.e., not stopped).
+LUA_GCGEN:
+changes the collector to generational mode
+(see §2.5).
+LUA_GCINC:
+changes the collector to incremental mode.
+This is the default mode.
+
+For more details about these options,
+see collectgarbage.
+
+
+
+
+
+
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 passed to lua_newstate.
+
+
+
+
+
+
lua_getctx+[-0, +0, –] +
int lua_getctx (lua_State *L, int *ctx);+ +
+This function is called by a continuation function (see §4.7) +to retrieve the status of the thread and a context information. + + +
+When called in the original function,
+lua_getctx always returns LUA_OK
+and does not change the value of its argument ctx.
+When called inside a continuation function,
+lua_getctx returns LUA_YIELD and sets
+the value of ctx to be the context information
+(the value passed as the ctx argument
+to the callee together with the continuation function).
+
+
+
+When the callee is lua_pcallk,
+Lua may also call its continuation function
+to handle errors during the call.
+That is, upon an error in the function called by lua_pcallk,
+Lua may not return to the original function
+but instead may call the continuation function.
+In that case, a call to lua_getctx will return the error code
+(the value that would be returned by lua_pcallk);
+the value of ctx will be set to the context information,
+as in the case of a yield.
+
+
+
+
+
+
lua_getfield+[-0, +1, e] +
void 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).
+
+
+
+
+
+
lua_getglobal+[-0, +1, e] +
void lua_getglobal (lua_State *L, const char *name);+ +
+Pushes onto the stack the value of the global name.
+
+
+
+
+
+
lua_getmetatable+[-0, +(0|1), –] +
int lua_getmetatable (lua_State *L, int index);+ +
+Pushes onto the stack the metatable of the value at the given index. +If the value does not have a metatable, +the function returns 0 and pushes nothing on the stack. + + + + + +
lua_gettable+[-1, +1, e] +
void 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 at the top of the stack.
+
+
+
+This function pops the key from the stack +(putting the resulting value in its place). +As in Lua, this function may trigger a metamethod +for the "index" event (see §2.4). + + + + + +
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 +(and so 0 means an empty stack). + + + + + +
lua_getuservalue+[-0, +1, –] +
void lua_getuservalue (lua_State *L, int index);+ +
+Pushes onto the stack the Lua value associated with the userdata +at the given index. +This Lua value must be a table or nil. + + + + + +
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 ptrdiff_t lua_Integer;+ +
+The type used by the Lua API to represent signed integral values. + + +
+By default it is a ptrdiff_t,
+which is usually the largest signed integral type the machine handles
+"comfortably".
+
+
+
+
+
+
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_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_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 §3.4.6).
+The result is pushed on the stack.
+
+
+
+
+
+
lua_load+[-0, +1, –] +
int lua_load (lua_State *L, + lua_Reader reader, + void *data, + const char *source, + 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 return values of lua_load are:
+
+
LUA_OK: no errors;LUA_ERRSYNTAX:
+syntax error during precompilation;LUA_ERRMEM:
+memory allocation error;LUA_ERRGCMM:
+error while running a __gc metamethod.
+(This error has no relation with the chunk being loaded.
+It is generated by the garbage collector.)
+
+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 source argument gives a name to the chunk,
+which is used for error messages and in debug information (see §4.9).
+
+
+
+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 should always leave the stack
+unmodified when returning.
+
+
+
+If the resulting function has one upvalue,
+this upvalue is set to the value of the global environment
+stored at index LUA_RIDX_GLOBALS in the registry (see §4.5).
+When loading main chunks,
+this upvalue will be the _ENV variable (see §2.2).
+
+
+
+
+
+
lua_newstate+[-0, +0, –] +
lua_State *lua_newstate (lua_Alloc f, void *ud);+ +
+Creates a new thread running in a new, independent state.
+Returns NULL if cannot create the thread or the state
+(due to lack of memory).
+The argument f is the allocator function;
+Lua does all memory allocation for this state through this function.
+The second argument, ud, is an opaque pointer that Lua
+passes to the allocator in every call.
+
+
+
+
+
+
lua_newtable+[-0, +1, e] +
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, e] +
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.
+
+
+
+There is no explicit function to close or to destroy a thread. +Threads are subject to garbage collection, +like any Lua object. + + + + + +
lua_newuserdata+[-0, +1, e] +
void *lua_newuserdata (lua_State *L, size_t size);+ +
+This function allocates a new block of memory with the given size, +pushes onto the stack a new full userdata with the block address, +and returns this address. +The host program can freely use this memory. + + + + + +
lua_next+[-1, +(2|0), e] +
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 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,
+do not call 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.
+
+
+
+See function next for the caveats of modifying
+the table during its traversal.
+
+
+
+
+
+
lua_Numbertypedef double lua_Number;+ +
+The type of numbers in Lua.
+By default, it is double, but that can be changed in luaconf.h.
+Through this configuration file you can change
+Lua to operate with another type for numbers (e.g., float or long).
+
+
+
+
+
+
lua_pcall+[-(nargs + 1), +(nresults|1), –] +
int lua_pcall (lua_State *L, int nargs, int nresults, int msgh);+ +
+Calls a function 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 message),
+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 message returned on the stack
+is exactly the original error message.
+Otherwise, msgh is the stack index of a
+message handler.
+(In the current implementation, this index cannot be a pseudo-index.)
+In case of runtime errors,
+this function will be called with the error message
+and its return value will be the message
+returned on the stack by lua_pcall.
+
+
+
+Typically, the message handler is used to add more debug
+information to the error message, 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 codes
+(defined in lua.h):
+
+
LUA_OK (0):
+success.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_ERRGCMM:
+error while running a __gc metamethod.
+(This error typically has no relation with the function being called.
+It is generated by the garbage collector.)
+lua_pcallk+[-(nargs + 1), +(nresults|1), –] +
int lua_pcallk (lua_State *L, + int nargs, + int nresults, + int errfunc, + int ctx, + lua_CFunction k);+ +
+This function behaves exactly like lua_pcall,
+but allows the called function to yield (see §4.7).
+
+
+
+
+
+
lua_pop+[-n, +0, –] +
void lua_pop (lua_State *L, int n);+ +
+Pops n elements from the stack.
+
+
+
+
+
+
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, e] +
void lua_pushcclosure (lua_State *L, lua_CFunction fn, int n);+ +
+Pushes a new C closure onto the stack. + + +
+When a C function is created,
+it is possible to associate some values with it,
+thus creating a C closure (see §4.4);
+these values are then accessible to the function whenever it is called.
+To associate values with a C function,
+first these values should be pushed onto the stack
+(when there are multiple values, 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 should 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 throws 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 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.
+
+
+
+Any function to be registered in Lua must
+follow the correct protocol to receive its parameters
+and return its results (see lua_CFunction).
+
+
+
+lua_pushcfunction is defined as a macro:
+
+
+ #define lua_pushcfunction(L,f) lua_pushcclosure(L,f,0) +
+Note that f is used twice.
+
+
+
+
+
+
lua_pushfstring+[-0, +1, e] +
const char *lua_pushfstring (lua_State *L, const char *fmt, ...);+ +
+Pushes onto the stack a formatted string
+and returns a pointer to this string.
+It is similar to the ANSI C function sprintf,
+but has some important differences:
+
+
%%' (inserts a '%' in the string),
+'%s' (inserts a zero-terminated string, with no size restrictions),
+'%f' (inserts a lua_Number),
+'%p' (inserts a pointer as a hexadecimal numeral),
+'%d' (inserts an int), and
+'%c' (inserts an int as a byte).
+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 a number 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, e] +
const char *lua_pushliteral (lua_State *L, const char *s);+ +
+This macro is equivalent to lua_pushlstring,
+but can be used only when s is a literal string.
+It automatically provides the string length.
+
+
+
+
+
+
lua_pushlstring+[-0, +1, e] +
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 makes (or reuses) 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. + + + + + +
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 number with value n onto the stack.
+
+
+
+
+
+
lua_pushstring+[-0, +1, e] +
const char *lua_pushstring (lua_State *L, const char *s);+ +
+Pushes the zero-terminated string pointed to by s
+onto the stack.
+Lua makes (or reuses) 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. + + +
+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_pushunsigned+[-0, +1, –] +
void lua_pushunsigned (lua_State *L, lua_Unsigned n);+ +
+Pushes a number with value n onto the stack.
+
+
+
+
+
+
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, e] +
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, without calling metamethods).
+Otherwise returns 0.
+Also returns 0 if any of the indices are non valid.
+
+
+
+
+
+
lua_rawget+[-1, +1, –] +
void lua_rawget (lua_State *L, int index);+ +
+Similar to lua_gettable, but does a raw access
+(i.e., without metamethods).
+
+
+
+
+
+
lua_rawgeti+[-0, +1, –] +
void lua_rawgeti (lua_State *L, int index, int 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 invoke metamethods.
+
+
+
+
+
+
lua_rawgetp+[-0, +1, –] +
void 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 invoke metamethods.
+
+
+
+
+
+
lua_rawlen+[-0, +0, –] +
size_t 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, it is 0.
+
+
+
+
+
+
lua_rawset+[-2, +0, e] +
void lua_rawset (lua_State *L, int index);+ +
+Similar to lua_settable, but does a raw assignment
+(i.e., without metamethods).
+
+
+
+
+
+
lua_rawseti+[-1, +0, e] +
void lua_rawseti (lua_State *L, int index, int n);+ +
+Does the equivalent of t[n] = v,
+where t is the table at the given index
+and v is the value at the top of the stack.
+
+
+
+This function pops the value from the stack. +The assignment is raw; +that is, it does not invoke metamethods. + + + + + +
lua_rawsetp+[-1, +0, e] +
void lua_rawsetp (lua_State *L, int index, const void *p);+ +
+Does the equivalent of t[k] = v,
+where t is the table at the given index,
+k is the pointer p represented as a light userdata,
+and v is the value at the top of the stack.
+
+
+
+This function pops the value from the stack. +The assignment is raw; +that is, it does not invoke metamethods. + + + + + +
lua_Readertypedef const char * (*lua_Reader) (lua_State *L, + void *data, + size_t *size);+ +
+The reader function used by lua_load.
+Every time it needs another piece of the chunk,
+lua_load 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 the given index), +and then pops the top element. + + + + + +
lua_resume+[-?, +?, –] +
int lua_resume (lua_State *L, lua_State *from, int nargs);+ +
+Starts and resumes a coroutine in a given thread. + + +
+To start a coroutine,
+you push onto the thread stack the main function plus any arguments;
+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, the stack contains all values passed to lua_yield,
+or all values 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 lua_pcall).
+
+
+
+In case of errors, +the stack is not unwound, +so you can use the debug API over it. +The error message is on the top of the stack. + + +
+To resume a coroutine,
+you remove any results from the last lua_yield,
+put on its stack only 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_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 at 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_setmetatable+[-1, +0, –] +
void lua_setmetatable (lua_State *L, int index);+ +
+Pops a table from the stack and +sets it as the new metatable for the value at the given index. + + + + + +
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 at 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+[-?, +?, –] +
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 larger than the old one,
+then the new elements are filled with nil.
+If index is 0, then all stack elements are removed.
+
+
+
+
+
+
lua_setuservalue+[-1, +0, –] +
void lua_setuservalue (lua_State *L, int index);+ +
+Pops a table or nil from the stack and sets it as +the new value associated to the userdata at the given index. + + + + + +
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 0 (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 only call functions 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_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_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 a number or a string convertible to a number
+(see §3.4.2);
+otherwise, lua_tointegerx returns 0.
+
+
+
+If the number is not an integer, +it is truncated in some non-specified way. + + +
+If isnum is not NULL,
+its referent is assigned a boolean value that
+indicates whether the operation succeeded.
+
+
+
+
+
+
lua_tolstring+[-0, +0, e] +
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 also 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 fully aligned pointer
+to a string inside the Lua state.
+This string always has a zero ('\0')
+after its last character (as in C),
+but can contain other zeros in its body.
+Because Lua has garbage collection,
+there is no guarantee that the pointer returned by lua_tolstring
+will be valid after the corresponding value is removed from the stack.
+
+
+
+
+
+
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 §3.4.2);
+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, 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 debug information. + + + + + +
lua_tostring+[-0, +0, e] +
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_tounsigned+[-0, +0, –] +
lua_Unsigned lua_tounsigned (lua_State *L, int index);+ +
+Equivalent to lua_tounsignedx with isnum equal to NULL.
+
+
+
+
+
+
lua_tounsignedx+[-0, +0, –] +
lua_Unsigned lua_tounsignedx (lua_State *L, int index, int *isnum);+ +
+Converts the Lua value at the given index
+to the unsigned integral type lua_Unsigned.
+The Lua value must be a number or a string convertible to a number
+(see §3.4.2);
+otherwise, lua_tounsignedx returns 0.
+
+
+
+If the number is not an integer, +it is truncated in some non-specified way. +If the number is outside the range of representable values, +it is normalized to the remainder of its division by +one more than the maximum representable value. + + +
+If isnum is not NULL,
+its referent is assigned a boolean value that
+indicates whether the operation succeeded.
+
+
+
+
+
+
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 block address.
+If the value is a light userdata,
+returns its 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 unsigned long lua_Unsigned;+ +
+The type used by the Lua API to represent unsigned integral values. +It must have at least 32 bits. + + +
+By default it is an unsigned int or an unsigned long,
+whichever can hold 32-bit values.
+
+
+
+
+
+
lua_upvalueindex+[-0, +0, –] +
int lua_upvalueindex (int i);+ +
+Returns the pseudo-index that represents the i-th upvalue of
+the running function (see §4.4).
+
+
+
+
+
+
lua_version+[-0, +0, v] +
const lua_Number *lua_version (lua_State *L);+ +
+Returns the address of the version number stored in the Lua core.
+When called with a valid lua_State,
+returns the address of the version used to create that state.
+When called with NULL,
+returns the address of the version running the call.
+
+
+
+
+
+
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 it produces another piece of chunk,
+lua_dump calls the writer,
+passing along the buffer to be written (p),
+its size (sz),
+and the data 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+[-?, +?, –] +
int lua_yield (lua_State *L, int nresults);+ +
+This function is equivalent to lua_yieldk,
+but it has no continuation (see §4.7).
+Therefore, when the thread resumes,
+it returns to the function that called
+the function calling lua_yield.
+
+
+
+
+
+
lua_yieldk+[-?, +?, –] +
int lua_yieldk (lua_State *L, int nresults, int ctx, lua_CFunction k);+ +
+Yields a coroutine. + + +
+This function should only be called as the +return expression of a C function, as follows: + +
+ return lua_yieldk (L, n, i, k); +
+When a C function calls lua_yieldk in that way,
+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 are 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 §4.7).
+This continuation function receives the same stack
+from the previous function,
+with the results removed and
+replaced by the arguments passed to lua_resume.
+Moreover,
+the continuation function may access the value ctx
+by calling lua_getctx.
+
+
+
+
+
+
+
+
+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) */
+ 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) */
+ 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,
+call 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 describe the source in a user-dependent manner.
+Otherwise,
+the function was defined in a string where
+source is that string.
+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 fixed parameters of the function
+(always 0 for C functions).
+isvararg:
+true if the function is a vararg function
+(always true for C functions).
+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), e] +
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:
+
+
n': fills in the field name and namewhat;
+S':
+fills in the fields source, short_src,
+linedefined, lastlinedefined, and what;
+l': fills in the field currentline;
+t': fills in the field istailcall;
+u': fills in the fields
+nups, nparams, and isvararg;
+f':
+pushes onto the stack the function that is
+running at the given level;
+L':
+pushes onto the stack a table whose indices are the
+numbers of the lines that are valid on the function.
+(A valid line is a line with some associated code,
+that is, a line where you can put a break point.
+Non-valid lines include empty lines and comments.)
+
+This function returns 0 on error
+(for instance, an invalid option in what).
+
+
+
+
+
+
lua_getlocal+[-0, +(0|1), –] +
const char *lua_getlocal (lua_State *L, lua_Debug *ar, int n);+ +
+Gets information about a local variable 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 should be NULL and the function
+to be inspected must be at 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 on the stack).
+When there are no errors, lua_getstack returns 1;
+when called with a level greater than the stack depth,
+it returns 0.
+
+
+
+
+
+
lua_getupvalue+[-0, +(0|1), –] +
const char *lua_getupvalue (lua_State *L, int funcindex, int n);+ +
+Gets information about a closure's upvalue.
+(For Lua functions,
+upvalues are the external local variables that the function uses,
+and that are consequently included in its closure.)
+lua_getupvalue gets the index n of an upvalue,
+pushes the upvalue's value onto the stack,
+and returns its name.
+funcindex points to the closure in the stack.
+(Upvalues have no particular order,
+as they are active through the whole function.
+So, they are numbered in an arbitrary order.)
+
+
+
+Returns NULL (and pushes nothing)
+when the index is greater than the number of upvalues.
+For C functions, this function uses the empty string ""
+as a name for all 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
+and they cannot yield any value;
+to yield a hook function must finish its execution
+calling lua_yield with nresults equal to zero.
+
+
+
+
+
+
lua_sethook+[-0, +0, –] +
int 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.)
+
+A hook is disabled by setting mask to zero.
+
+
+
+
+
+
lua_setlocal+[-(0|1), +0, –] +
const char *lua_setlocal (lua_State *L, lua_Debug *ar, int n);+ +
+Sets the value of a local variable of a given activation record.
+Parameters ar and n are as in lua_getlocal
+(see lua_getlocal).
+lua_setlocal assigns the value at 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.
+
+
+
+
+
+
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 at the top of the stack
+to the upvalue and returns its name.
+It also pops the value from the stack.
+Parameters funcindex and n are as in the lua_getupvalue
+(see lua_getupvalue).
+
+
+
+Returns NULL (and pops nothing)
+when the index is greater than the number of upvalues.
+
+
+
+
+
+
lua_upvalueid+[-0, +0, –] +
void *lua_upvalueid (lua_State *L, int funcindex, int n);+ +
+Returns an unique identifier for the upvalue numbered n
+from the closure at index funcindex.
+Parameters funcindex and n are as in the lua_getupvalue
+(see lua_getupvalue)
+(but n cannot be greater than the number of upvalues).
+
+
+
+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. + + + + + +
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 throw an error if the check is not satisfied.
+
+
+
+
+Here we list all functions and types from the auxiliary library +in alphabetical order. + + + +
luaL_addchar+[-?, +?, e] +
void luaL_addchar (luaL_Buffer *B, char c);+ +
+Adds the byte c to the buffer B
+(see luaL_Buffer).
+
+
+
+
+
+
luaL_addlstring+[-?, +?, e] +
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+[-?, +?, e] +
void luaL_addsize (luaL_Buffer *B, size_t n);+ +
+Adds to the buffer B (see luaL_Buffer)
+a string of length n previously copied to the
+buffer area (see luaL_prepbuffer).
+
+
+
+
+
+
luaL_addstring+[-?, +?, e] +
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).
+The string cannot contain embedded zeros.
+
+
+
+
+
+
luaL_addvalue+[-1, +?, e] +
void luaL_addvalue (luaL_Buffer *B);+ +
+Adds the value at 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 not, raises an error with a standard message.
+
+
+
+
+
+
luaL_argerror+[-0, +0, v] +
int luaL_argerror (lua_State *L, int arg, const char *extramsg);+ +
+Raises an error with a standard message
+that includes extramsg as a comment.
+
+
+
+This function never returns,
+but it is an idiom to use it in C functions
+as return luaL_argerror(args).
+
+
+
+
+
+
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 total 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.
+
+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_buffinit+[-0, +0, –] +
void luaL_buffinit (lua_State *L, luaL_Buffer *B);+ +
+Initializes a buffer B.
+This function does not allocate any space;
+the buffer must be declared as a variable
+(see luaL_Buffer).
+
+
+
+
+
+
luaL_buffinitsize+[-?, +?, e] +
char *luaL_buffinitsize (lua_State *L, luaL_Buffer *B, size_t sz);+ +
+Equivalent to the sequence
+luaL_buffinit, luaL_prepbuffsize.
+
+
+
+
+
+
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_checkint+[-0, +0, v] +
int luaL_checkint (lua_State *L, int arg);+ +
+Checks whether the function argument arg is a number
+and returns this number cast to an int.
+
+
+
+
+
+
luaL_checkinteger+[-0, +0, v] +
lua_Integer luaL_checkinteger (lua_State *L, int arg);+ +
+Checks whether the function argument arg is a number
+and returns this number cast to a lua_Integer.
+
+
+
+
+
+
luaL_checklong+[-0, +0, v] +
long luaL_checklong (lua_State *L, int arg);+ +
+Checks whether the function argument arg is a number
+and returns this number cast to a long.
+
+
+
+
+
+
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 *l
+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.
+
+
+
+
+
+
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 address (see lua_touserdata).
+
+
+
+
+
+
luaL_checkunsigned+[-0, +0, v] +
lua_Unsigned luaL_checkunsigned (lua_State *L, int arg);+ +
+Checks whether the function argument arg is a number
+and returns this number cast to a lua_Unsigned.
+
+
+
+
+
+
luaL_checkversion+[-0, +0, –] +
void luaL_checkversion (lua_State *L);+ +
+Checks whether the core running the call, +the core that created the Lua state, +and the code making the call are all using the same version of Lua. +Also checks whether the core running the call +and the core that created the Lua state +are using the same address space. + + + + + +
luaL_dofile+[-0, +?, e] +
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 false if there are no errors +or true 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 false if there are no errors +or true 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, e] +
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), e] +
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), e] +
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.
+If the object does not have a metatable,
+or if the metatable does not have this field,
+returns false and pushes nothing.
+
+
+
+
+
+
luaL_getmetatable+[-0, +1, –] +
void luaL_getmetatable (lua_State *L, const char *tname);+ +
+Pushes onto the stack the metatable associated with name tname
+in the registry (see luaL_newmetatable).
+
+
+
+
+
+
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, e] +
const char *luaL_gsub (lua_State *L, + const char *s, + const char *p, + const char *r);+ +
+Creates a copy of string s by 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] +
int 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 §3.4.6).
+Raises an error if the result of the operation is not a number.
+(This case only can 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 function lua_load.
+
+
+
+
+
+
luaL_loadfile+[-0, +1, e] +
int luaL_loadfile (lua_State *L, const char *filename);+ +
+Equivalent to luaL_loadfilex with mode equal to NULL.
+
+
+
+
+
+
luaL_loadfilex+[-0, +1, e] +
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 function lua_load.
+
+
+
+This function returns the same results as lua_load,
+but it has an extra error code LUA_ERRFILE
+if it cannot open/read the file or the file has a wrong mode.
+
+
+
+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, e] +
void luaL_newlib (lua_State *L, const luaL_Reg *l);+ +
+Creates a new table and registers there
+the functions in list l.
+It is implemented as the following macro:
+
+
+ (luaL_newlibtable(L,l), luaL_setfuncs(L,l,0)) ++ + + + +
luaL_newlibtable+[-0, +1, e] +
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, e] +
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 it to the registry with key tname,
+and returns 1.
+
+
+
+In both cases 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 standard C realloc function
+and then sets a panic function (see §4.6) that prints
+an error message to the standard error output in case of fatal
+errors.
+
+
+
+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_optint+[-0, +0, v] +
int luaL_optint (lua_State *L, int arg, int d);+ +
+If the function argument arg is a number,
+returns this number cast to an int.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+
+
+
luaL_optinteger+[-0, +0, v] +
lua_Integer luaL_optinteger (lua_State *L, + int arg, + lua_Integer d);+ +
+If the function argument arg is a number,
+returns this number cast to a lua_Integer.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
+
+
+
luaL_optlong+[-0, +0, v] +
long luaL_optlong (lua_State *L, int arg, long d);+ +
+If the function argument arg is a number,
+returns this number cast to a long.
+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 the position *l with the result's length.
+
+
+
+
+
+
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.
+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_optunsigned+[-0, +0, v] +
lua_Unsigned luaL_optunsigned (lua_State *L, + int arg, + lua_Unsigned u);+ +
+If the function argument arg is a number,
+returns this number cast to a lua_Unsigned.
+If this argument is absent or is nil,
+returns u.
+Otherwise, raises an error.
+
+
+
+
+
+
luaL_prepbuffer+[-?, +?, e] +
char *luaL_prepbuffer (luaL_Buffer *B);+ +
+Equivalent to luaL_prepbuffsize
+with the predefined size LUAL_BUFFERSIZE.
+
+
+
+
+
+
luaL_prepbuffsize+[-?, +?, e] +
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_pushresult+[-?, +1, e] +
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, e] +
void luaL_pushresultsize (luaL_Buffer *B, size_t sz);+ +
+Equivalent to the sequence luaL_addsize, luaL_pushresult.
+
+
+
+
+
+
luaL_ref+[-1, +0, e] +
int luaL_ref (lua_State *L, int t);+ +
+Creates and returns a reference,
+in the table at index t,
+for the object at 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 table t,
+luaL_ref ensures the uniqueness of the key it returns.
+You can retrieve an object referred by reference r
+by calling lua_rawgeti(L, t, r).
+Function luaL_unref frees a reference and its associated object.
+
+
+
+If the object at 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 an 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);+ +
+Calls function openf with string modname as an argument
+and sets the call result in package.loaded[modname],
+as if that function has been called through require.
+
+
+
+If glb is true,
+also stores the result into global modname.
+
+
+
+Leaves a copy of that result on the stack. + + + + + +
luaL_setfuncs+[-nup, +0, e] +
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 sharing nup upvalues,
+which must be previously pushed on the stack
+on top of the library table.
+These values are popped from the stack after the registration.
+
+
+
+
+
+
luaL_setmetatable+[-0, +0, –] +
void luaL_setmetatable (lua_State *L, const char *tname);+ +
+Sets the metatable of the object at the top of the stack
+as the metatable associated with name tname
+in the registry (see luaL_newmetatable).
+
+
+
+
+
+
luaL_testudata+[-0, +0, e] +
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 throwing 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.
+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, e] +
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_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 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, e] +
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 directly 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 are quite useful or have critical performance requirements that
+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. +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_table (for the table library),
+luaopen_math (for the mathematical library),
+luaopen_bit32 (for the bit 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])v is false (i.e., nil or false);
+otherwise, returns all its arguments.
+message is an error message;
+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) and
+a second value with the total memory in bytes modulo 1024.
+The first value has a fractional part,
+so the following equality is always true:
+
+
+ k, b = collectgarbage("count")
+ assert(k*1024 == math.floor(k)*1024 + b)
++(The second result is useful when Lua is compiled +with a non floating-point type for numbers.) +
step":
+performs a garbage-collection step.
+The step "size" is controlled by arg
+(larger values mean more steps) in a non-specified way.
+If you want to control the step size
+you must experimentally tune the value of arg.
+Returns true if the step finished a collection cycle.
+setpause":
+sets arg as the new value for the pause of
+the collector (see §2.5).
+Returns the previous value for pause.
+setstepmul":
+sets arg as the new value for the step multiplier of
+the collector (see §2.5).
+Returns the previous value for step.
+isrunning":
+returns a boolean that tells whether the collector is running
+(i.e., not stopped).
+generational":
+changes the collector to generational mode.
+This is an experimental feature (see §2.5).
+incremental":
+changes the collector to incremental mode.
+This is the default mode.
++
dofile ([filename])dofile executes the contents 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 message.
+Function error 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)
+If t has a metamethod __ipairs,
+calls it with t as argument and returns the first three
+results from the call.
+
+
+
+Otherwise,
+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 pairs (1,t[1]), (2,t[2]), ...,
+up to the first integer key absent from the table.
+
+
+
+
+
+
load (ld [, source [, mode [, env]]])+Loads a chunk. + + +
+If ld is a string, the chunk is this string.
+If ld is a function,
+load calls it repeatedly to get the chunk pieces.
+Each call to ld 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, +returns the compiled chunk as a function; +otherwise, returns nil plus the error message. + + +
+If the resulting function has upvalues,
+the first upvalue is set to the value of env,
+if that parameter is given,
+or to the value of the global environment.
+(When you load a main chunk,
+the resulting function will always have exactly one upvalue,
+the _ENV variable (see §2.2).
+When you load a binary chunk created from a function (see string.dump),
+the resulting function can have arbitrary upvalues.)
+
+
+
+source is used as the source of the chunk for error messages
+and debug information (see §4.9).
+When absent,
+it defaults to ld, if ld 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".
+
+
+
+
+
+
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.
+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 numeric order, +use a numerical for.) + + +
+The behavior of next is undefined if,
+during the traversal,
+you assign any value to a non-existent field in the table.
+You may however modify existing fields.
+In particular, you may clear existing fields.
+
+
+
+
+
+
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 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 message.
+
+
+
+
+
+
print (···)stdout,
+using the tostring function to convert each argument to a string.
+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 any metamethod.
+Returns a boolean.
+
+
+
+
++
rawget (table, index)table[index],
+without invoking any metamethod.
+table must be a table;
+index may be any value.
+
+
+
+
++
rawlen (v)v,
+which must be a table or a string,
+without invoking any metamethod.
+Returns an integer number.
+
+
+
+
++
rawset (table, index, value)table[index] to value,
+without invoking any metamethod.
+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.
+(You cannot change the metatable of other types from Lua, only from C.)
+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.
+
+
+
+
+
+
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 (see §3.4.2),
+then tonumber returns this number;
+otherwise, it returns nil.
+
+
+
+When called with base,
+then e should 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 nil.
+
+
+
+
+
+
tostring (v)string.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.
+
+
+
+
+
+
type (v)nil" (a string, not the value nil),
+"number",
+"string",
+"boolean",
+"table",
+"function",
+"thread",
+and "userdata".
+
+
+
+
++
_VERSIONLua 5.2".
+
+
+
+
++
xpcall (f, msgh [, arg1, ···])
+This function is similar to pcall,
+except that it sets a new message handler msgh.
+
+
+
+
+
+
+
+
+The operations related to coroutines comprise a sub-library of
+the basic library and come inside the table coroutine.
+See §2.6 for a general description of coroutines.
+
+
+
+
coroutine.create (f)
+Creates a new coroutine, with body f.
+f must be a Lua function.
+Returns this new coroutine,
+an object with type "thread".
+
+
+
+
+
+
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
+(if the coroutine yields) or any values returned by the body function
+(if 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 coroutine co, as a string:
+"running",
+if the coroutine is running (that is, it 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 Lua function.
+Returns a function that resumes the coroutine each time it is called.
+Any arguments passed to the function behave as the
+extra arguments to resume.
+Returns the same values returned by resume,
+except the first boolean.
+In case of error, 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 a 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].
+Otherwise, it tries to find a loader for the module.
+
+
+
+To find a loader,
+require is guided by the package.searchers sequence.
+By changing this sequence,
+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 should 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 dependent on how it got the loader.
+(If the loader came from a file,
+this extra value is the file name.)
+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].
+
+
+
+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
+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_2
+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.
+
+
+
+
+
+
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 function is not supported by Standard 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).
+
+
+
+
+
+
package.path
+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_2 or
+the environment variable LUA_PATH or
+with a default path defined in luaconf.h,
+if those environment variables are not defined.
+Any ";;" 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.
+
+
+
+
+
+
package.searchers
+A table used by require to control how to load 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 parameter.
+The function can return another function (the module loader)
+plus an extra value that will be passed to that loader,
+or a string explaining why it did not find that module
+(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 prefix up to (and including) the first hyphen is removed.
+For instance, if the module name is a.v1-b.c,
+the function name will be luaopen_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 name where the module was found,
+as returned by package.searchpath.
+The first searcher returns no extra value.
+
+
+
+
+
+
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 nil 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.
+
+
++Numerical codes are not necessarily portable across platforms. + + + + +
+
string.char (···)+Numerical codes are not necessarily portable across platforms. + + + + +
+
string.dump (function)
+Returns a string containing a binary representation of the given function,
+so that a later load on this string returns
+a copy of the function (but with new upvalues).
+
+
+
+
+
+
string.find (s, pattern [, init [, plain]])
+Looks for the first match of
+pattern 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 nil.
+A third, optional numerical argument init specifies
+where to start the search;
+its default value is 1 and can be negative.
+A value of 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.
+Note that if plain is given, then init must be given as well.
+
+
+
+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 ANSI C function sprintf.
+The only differences are that the options/modifiers
+*, h, L, l, n,
+and p are not supported
+and that there is an extra option, q.
+The q option formats a string 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" ++ +
+Options
+A and a (when available),
+E, e, f,
+G, and g all expect a number as argument.
+Options c, d,
+i, o, u, X, and x
+also expect a number,
+but the range of that number may be limited by
+the underlying C implementation.
+For options o, u, X, and x,
+the number cannot be negative.
+Option q expects a string;
+option s expects a string without embedded zeros.
+If the argument to option s is not a string,
+it is converted to one following the same rules of tostring.
+
+
+
+
+
+
string.gmatch (s, pattern)pattern over the string s.
+If pattern specifies no captures,
+then the whole match is produced in each call.
+
+
+
+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 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="5.2"}
+ x = string.gsub("$name-$version.tar.gz", "%$(%w+)", t)
+ --> x="lua-5.2.tar.gz"
+
+
+
+
++
string.len (s)"" has length 0.
+Embedded zeros are counted,
+so "a\000bc\000" has length 5.
+
+
+
+
++
string.lower (s)+
string.match (s, pattern [, init])pattern in the string s.
+If it finds one, then match returns
+the captures from the pattern;
+otherwise it returns nil.
+If pattern specifies no captures,
+then the whole match is returned.
+A third, optional numerical argument init specifies
+where to start the search;
+its default value is 1 and can be negative.
+
+
+
+
++
string.rep (s, n [, sep])n copies of
+the string s separated by the string sep.
+The default value for sep is the empty string
+(that is, no separator).
+
+
+
+
++
string.reverse (s)s reversed.
+
+
+
+
++
string.sub (s, i [, j])s that
+starts at i and continues until j;
+i and j can be negative.
+If j is absent, then it is assumed to be equal to -1
+(which is the same as the string length).
+In particular,
+the call string.sub(s,1,j) returns a prefix of s
+with length j,
+and string.sub(s, -i) returns a suffix of s
+with length i.
+
+
+
+If, after the translation of negative indices,
+i is less than 1,
+it is corrected to 1.
+If j is greater than the string length,
+it is corrected to that length.
+If, after these corrections,
+i is greater than j,
+the function returns the empty string.
+
+
+
+
+
+
string.upper (s)+A character class is used to represent a set of characters. +The following combinations are allowed in describing a character class: + +
^$()%.[]*+-?)
+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 punctuation character (even the non magic)
+can be preceded by a '%'
+when used 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.
+
+
+
+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 0 or more repetitions of characters in the class.
+These repetition items will always match the longest possible sequence;
++',
+which matches 1 or more repetitions of characters in the class.
+These repetition items will always match the longest possible sequence;
+-',
+which also matches 0 or more repetitions of characters in the class.
+Unlike '*',
+these repetition items will always match the shortest possible sequence;
+?',
+which matches 0 or 1 occurrence of a character in the class;
+%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 empty 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.
+
+
+
+
+
+
+
+
+
+
+
+
+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,
+the table should be a proper sequence
+or have a __len metamethod (see §3.4.6).
+All functions ignore non-numeric keys
+in tables given as arguments.
+
+
+
+For performance reasons, +all table accesses (get/set) performed by these functions are raw. + + +
+
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 list t.
+
+
+
+
+
+
table.pack (···)
+Returns a new table with all parameters stored into keys 1, 2, etc.
+and with a field "n" with the total number of parameters.
+Note that the resulting table may not be a sequence.
+
+
+
+
+
+
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;
+in those cases, the function erases the element list[pos].
+
+
+
+The default value for pos is #list,
+so that a call table.remove(t) removes the last element
+of list t.
+
+
+
+
+
+
table.sort (list [, comp])
+Sorts 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 not comp(list[i+1],list[i]) will be true after the sort).
+If comp is not given,
+then the standard Lua operator < is used instead.
+
+
+
+The sort algorithm is not stable; +that is, 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 table. +This function is equivalent to + +
+ return list[i], list[i+1], ···, list[j] +
+By default, i is 1 and j is #list.
+
+
+
+
+
+
+
+
+This library is an interface to the standard C math library.
+It provides all its functions inside the table math.
+
+
+
+
math.abs (x)
+Returns the absolute value of x.
+
+
+
+
+
+
math.acos (x)
+Returns the arc cosine of x (in radians).
+
+
+
+
+
+
math.asin (x)
+Returns the arc sine of x (in radians).
+
+
+
+
+
+
math.atan (x)
+Returns the arc tangent of x (in radians).
+
+
+
+
+
+
math.atan2 (y, x)
+Returns the arc tangent of y/x (in radians),
+but uses the signs of both parameters to find the
+quadrant of the result.
+(It also handles correctly the case of x being zero.)
+
+
+
+
+
+
math.ceil (x)
+Returns the smallest integer larger than or equal to x.
+
+
+
+
+
+
math.cos (x)
+Returns the cosine of x (assumed to be in radians).
+
+
+
+
+
+
math.cosh (x)
+Returns the hyperbolic cosine of x.
+
+
+
+
+
+
math.deg (x)
+Returns the angle x (given in radians) in degrees.
+
+
+
+
+
+
math.exp (x)+Returns the value ex. + + + + +
+
math.floor (x)
+Returns the largest integer smaller 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.
+
+
+
+
+
+
math.frexp (x)
+Returns m and e such that x = m2e,
+e is an integer and the absolute value of m is
+in the range [0.5, 1)
+(or zero when x is zero).
+
+
+
+
+
+
math.huge
+The value HUGE_VAL,
+a value larger than or equal to any other numerical value.
+
+
+
+
+
+
math.ldexp (m, e)
+Returns m2e (e should be an integer).
+
+
+
+
+
+
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 maximum value among its arguments. + + + + +
+
math.min (x, ···)+Returns the minimum value among its arguments. + + + + +
+
math.modf (x)
+Returns two numbers,
+the integral part of x and the fractional part of x.
+
+
+
+
+
+
math.pi+The value of π. + + + + +
+
math.pow (x, y)
+Returns xy.
+(You can also use the expression x^y to compute this value.)
+
+
+
+
+
+
math.rad (x)
+Returns the angle x (given in degrees) in radians.
+
+
+
+
+
+
math.random ([m [, n]])
+This function is an interface to the simple
+pseudo-random generator function rand provided by Standard C.
+(No guarantees can be given for its statistical properties.)
+
+
+
+When called without arguments,
+returns a uniform pseudo-random real number
+in the range [0,1).
+When called with an integer number m,
+math.random returns
+a uniform pseudo-random integer in the range [1, m].
+When called with two integer numbers m and n,
+math.random returns a uniform pseudo-random
+integer in the range [m, n].
+
+
+
+
+
+
math.randomseed (x)
+Sets x as the "seed"
+for the pseudo-random generator:
+equal seeds produce equal sequences of numbers.
+
+
+
+
+
+
math.sin (x)
+Returns the sine of x (assumed to be in radians).
+
+
+
+
+
+
math.sinh (x)
+Returns the hyperbolic sine of x.
+
+
+
+
+
+
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.tanh (x)
+Returns the hyperbolic tangent of x.
+
+
+
+
+
+
+
+
+This library provides bitwise operations.
+It provides all its functions inside the table bit32.
+
+
+
+Unless otherwise stated,
+all functions accept numeric arguments in the range
+(-251,+251);
+each argument is normalized to
+the remainder of its division by 232
+and truncated to an integer (in some unspecified way),
+so that its final value falls in the range [0,232 - 1].
+Similarly, all results are in the range [0,232 - 1].
+Note that bit32.bnot(0) is 0xFFFFFFFF,
+which is different from -1.
+
+
+
+
bit32.arshift (x, disp)
+Returns the number x shifted disp bits to the right.
+The number disp may be any representable integer.
+Negative displacements shift to the left.
+
+
+
+This shift operation is what is called arithmetic shift.
+Vacant bits on the left are filled
+with copies of the higher bit of x;
+vacant bits on the right are filled with zeros.
+In particular,
+displacements with absolute values higher than 31
+result in zero or 0xFFFFFFFF (all original bits are shifted out).
+
+
+
+
+
+
bit32.band (···)+Returns the bitwise and of its operands. + + + + +
+
bit32.bnot (x)
+Returns the bitwise negation of x.
+For any integer x,
+the following identity holds:
+
+
+ assert(bit32.bnot(x) == (-1 - x) % 2^32) ++ + + +
+
bit32.bor (···)+Returns the bitwise or of its operands. + + + + +
+
bit32.btest (···)+Returns a boolean signaling +whether the bitwise and of its operands is different from zero. + + + + +
+
bit32.bxor (···)+Returns the bitwise exclusive or of its operands. + + + + +
+
bit32.extract (n, field [, width])
+Returns the unsigned number formed by the bits
+field to field + width - 1 from n.
+Bits are numbered from 0 (least significant) to 31 (most significant).
+All accessed bits must be in the range [0, 31].
+
+
+
+The default for width is 1.
+
+
+
+
+
+
bit32.replace (n, v, field [, width])
+Returns a copy of n with
+the bits field to field + width - 1
+replaced by the value v.
+See bit32.extract for details about field and width.
+
+
+
+
+
+
bit32.lrotate (x, disp)
+Returns the number x rotated disp bits to the left.
+The number disp may be any representable integer.
+
+
+
+For any valid displacement, +the following identity holds: + +
+ assert(bit32.lrotate(x, disp) == bit32.lrotate(x, disp % 32)) +
+In particular, +negative displacements rotate to the right. + + + + +
+
bit32.lshift (x, disp)
+Returns the number x shifted disp bits to the left.
+The number disp may be any representable integer.
+Negative displacements shift to the right.
+In any direction, vacant bits are filled with zeros.
+In particular,
+displacements with absolute values higher than 31
+result in zero (all bits are shifted out).
+
+
+
+For positive displacements, +the following equality holds: + +
+ assert(bit32.lshift(b, disp) == (b * 2^disp) % 2^32) ++ + + +
+
bit32.rrotate (x, disp)
+Returns the number x rotated disp bits to the right.
+The number disp may be any representable integer.
+
+
+
+For any valid displacement, +the following identity holds: + +
+ assert(bit32.rrotate(x, disp) == bit32.rrotate(x, disp % 32)) +
+In particular, +negative displacements rotate to the left. + + + + +
+
bit32.rshift (x, disp)
+Returns the number x shifted disp bits to the right.
+The number disp may be any representable integer.
+Negative displacements shift to the left.
+In any direction, vacant bits are filled with zeros.
+In particular,
+displacements with absolute values higher than 31
+result in zero (all bits are shifted out).
+
+
+
+For positive displacements, +the following equality holds: + +
+ assert(bit32.rshift(b, disp) == math.floor(b % 2^32 / 2^disp)) ++ +
+This shift operation is what is called logical shift. + + + + + + + +
+The I/O library provides two different styles for file manipulation. +The first one uses implicit file descriptors; +that is, there are operations to set a default input file and a +default output file, +and all input/output operations are over these default files. +The second style uses explicit file descriptors. + + +
+When using implicit file descriptors,
+all operations are supplied by table io.
+When using explicit file descriptors,
+the operation io.open returns a file descriptor
+and then all operations are supplied as methods of the file descriptor.
+
+
+
+The table io also provides
+three predefined file descriptors 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 nil on failure
+(plus an error message as a second result and
+a system-dependent error code as a third result)
+and some value different from nil 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 parameters, +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 detects the end of file,
+it returns nil (to finish the loop) and automatically closes the file.
+
+
+
+The call io.lines() (with no file name) is equivalent
+to io.input():lines();
+that is, it iterates over the lines of the default input file.
+In this case it does not close the file when the loop ends.
+
+
+
+In case of errors 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.
+It returns a new file handle,
+or, in case of errors, nil plus an error message.
+
+
+
+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 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 ()+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 nil 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.
+
+
+
+In case of errors this function raises the error, +instead of returning an error code. + + + + +
+
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 nil if it cannot read data with the specified format.
+When called without formats,
+it uses a default format that reads the next line
+(see below).
+
+
+
+The available formats are + +
*n":
+reads a number;
+this is the only format that returns a number instead of a string.
+*a":
+reads the whole file, starting at the current position.
+On end of file, it returns the empty string.
+*l":
+reads the next line skipping the end of line,
+returning nil on end of file.
+This is the default format.
+*L":
+reads the next line keeping the end of line (if present),
+returning nil on end of file.
++
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 nil,
+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 an output file. +There are three available modes: + +
no":
+no buffering; the result of any output operation appears immediately.
+full":
+full buffering; output operation is performed only
+when the buffer is full or when
+you explicitly flush the file (see io.flush).
+line":
+line buffering; output is buffered until a newline is output
+or there is any input from some special files
+(such as a terminal device).
+
+For the last two cases, size
+specifies the size of the buffer, in bytes.
+The default is an appropriate size.
+
+
+
+
+
+
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.
+Otherwise it returns nil plus a string describing the error.
+
+
+
+
+
+
+
+
+This library is implemented through table os.
+
+
+
+
os.clock ()+Returns an approximation of the amount in seconds of CPU time +used by the program. + + + + +
+
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 (four digits), month (1–12), day (1–31),
+hour (0–23), min (0–59), sec (0–61),
+wday (weekday, Sunday is 1),
+yday (day of the year),
+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 ANSI C function strftime.
+
+
+
+When called without arguments,
+date returns a reasonable date and time representation that depends on
+the host system and on the current locale
+(that is, os.date() is equivalent to os.date("%c")).
+
+
+
+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 number of seconds from time t1 to time t2.
+In POSIX, Windows, and some other systems,
+this value is exactly t2-t1.
+
+
+
+
+
+
os.execute ([command])
+This function is equivalent to the ANSI 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 nil otherwise.
+After this first result
+the function returns a string and 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 ANSI 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,
+closes the Lua state before exiting.
+
+
+
+
+
+
os.getenv (varname)
+Returns the value of the process environment variable varname,
+or nil 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 nil, +plus a string describing the error and the error code. + + + + +
+
os.rename (oldname, newname)
+Renames file or directory named oldname to newname.
+If this function fails, it returns nil,
+plus a string describing the error and the error code.
+
+
+
+
+
+
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 nil 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 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).
+For a description of these fields, see the os.date function.
+
+
+
+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.
+
+
+
+
+
+
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. + + +
+On 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 (§4.9) 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).
+
+
+
+
+
+
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 on the stack);
+and so on.
+If f is a number larger than the number of active functions,
+then getinfo returns nil.
+
+
+
+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.
+If present,
+the option 'f'
+adds a field named func with the function itself.
+If present,
+the option 'L'
+adds a field named activelines with the table of
+valid lines.
+
+
+
+For instance, the expression debug.getinfo(1,"n").name returns
+a table with 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, temporaries, etc.
+
+
+
+The first parameter or local variable has index 1, and so on,
+until the last active variable.
+Negative indices refer to vararg parameters;
+-1 is the first vararg parameter.
+The function returns nil 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 internal variables
+(loop control variables, temporaries, varargs, and C function locals).
+
+
+
+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 §4.5). + + + + +
+
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 nil if there is no upvalue with the given index.
+
+
+
+
+
+
debug.getuservalue (u)
+Returns the Lua value associated to u.
+If u is not a userdata,
+returns nil.
+
+
+
+
+
+
debug.sethook ([thread,] hook, mask [, count])
+Sets the given function as a hook.
+The string mask and the number count describe
+when the hook will be called.
+The string mask may have 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.
+With a count different from zero,
+the hook is called 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" (or "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 nil 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 nil if there is no upvalue
+with the given index.
+Otherwise, it returns the name of the upvalue.
+
+
+
+
+
+
debug.setuservalue (udata, value)
+Sets the given value as
+the Lua value associated to the given udata.
+value must be a table or nil;
+udata must be a full userdata.
+
+
+
+Returns udata.
+
+
+
+
+
+
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.
+An 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 an 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, including the debug library.
+Its usage is:
+
+
+ lua [options] [script [args]] +
+The options are: + +
-e stat: executes string stat;-l mod: "requires" mod;-i: enters interactive mode after running script;-v: prints version information;-E: ignores environment variables;--: stops handling options;-: executes stdin as a file and stops handling options.
+After handling its options, lua runs the given script,
+passing to it the given args as string arguments.
+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 option -E,
+the interpreter checks for an environment variable LUA_INIT_5_2
+(or LUA_INIT if it 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 option -E,
+besides ignoring LUA_INIT,
+Lua also ignores
+the values of LUA_PATH and LUA_CPATH,
+setting the values of
+package.path and package.cpath
+with the default paths defined in luaconf.h.
+
+
+
+All options are handled in order, except -i and -E.
+For instance, an invocation like
+
+
+ $ lua -e'a=1' -e 'print(a)' script.lua +
+will first set a to 1, then print the value of a,
+and finally run the file script.lua with no arguments.
+(Here $ is the shell prompt. Your prompt may be different.)
+
+
+
+Before starting to run the script,
+lua collects all arguments in the command line
+in a global table called arg.
+The script name is stored at 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 the options)
+go to negative indices.
+For instance, in the call
+
+
+ $ lua -la b.lua t1 t2 +
+the interpreter first runs the file a.lua,
+then creates a table
+
+
+ arg = { [-2] = "lua", [-1] = "-la",
+ [0] = "b.lua",
+ [1] = "t1", [2] = "t2" }
+
+and finally runs the file b.lua.
+The script is called with arg[1], arg[2], ...
+as arguments;
+it can also access these arguments with the vararg expression '...'.
+
+
+
+In interactive mode, +if you write an incomplete statement, +the interpreter waits for its completion +by issuing a different prompt. + + +
+In case of unprotected errors in the script,
+the interpreter reports the error to the standard error stream.
+If the error object is a string,
+the interpreter adds a stack traceback to it.
+Otherwise, if the error object has a metamethod __tostring,
+the interpreter calls this metamethod to produce the final message.
+Finally, if the error object is nil,
+the interpreter does not report the error.
+
+
+
+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,
+the standalone interpreter skips
+the first line of a 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 5.1 to Lua 5.2.
+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 next version of Lua.
+Similarly,
+all features marked as deprecated in Lua 5.1
+have been removed in Lua 5.2.
+
+
+
+
_ENV or the function load.
+
+
+
+C functions no longer have environments.
+Use an upvalue with a shared table if you need to keep
+shared state among several C functions.
+(You may use luaL_setfuncs to open a C library
+with all functions sharing a common upvalue.)
+
+
+
+To manipulate the "environment" of a userdata
+(which is now called user value),
+use the new functions
+lua_getuservalue and lua_setuservalue.
+
module is deprecated.
+It is easy to set up a module with regular Lua code.
+Modules are not expected to set global variables.
+setfenv and getfenv were removed,
+because of the changes in environments.
+math.log10 is deprecated.
+Use math.log with 10 as its second argument, instead.
+loadstring is deprecated.
+Use load instead; it now accepts string arguments
+and are exactly equivalent to loadstring.
+table.maxn is deprecated.
+Write it in Lua if you really need it.
+os.execute now returns true when command
+terminates successfully and nil plus error information
+otherwise.
+unpack was moved into the table library
+and therefore must be called as table.unpack.
+%z in patterns is deprecated,
+as now patterns may contain '\0' as a regular character.
+package.loaders was renamed package.searchers.
+load and loadfile)
+are potentially insecure when loading untrusted binary data.
+(Actually, those functions were already insecure because
+of flaws in the verification algorithm.)
+When in doubt,
+use the mode argument of those functions
+to restrict them to loading textual chunks.
+LUA_GLOBALSINDEX was removed.
+You must get the global environment from the registry
+(see §4.5).
+LUA_ENVIRONINDEX
+and functions lua_getfenv/lua_setfenv
+were removed,
+as C functions no longer have environments.
+luaL_register is deprecated.
+Use luaL_setfuncs so that your module does not create globals.
+(Modules are not expected to set global variables anymore.)
+osize argument to the allocation function
+may not be zero when creating a new block,
+that is, when ptr is NULL
+(see lua_Alloc).
+Use only the test ptr == NULL to check whether
+the block is new.
+__gc metamethods) for userdata are called in the
+reverse order that they were marked for finalization,
+not that they were created (see §2.5.1).
+(Most userdata are marked immediately after they are created.)
+Moreover,
+if the metatable does not have a __gc field when set,
+the finalizer will not be called,
+even if it is set later.
+luaL_typerror was removed.
+Write your own version if you need it.
+lua_cpcall is deprecated.
+You can simply push the function with lua_pushcfunction
+and call it with lua_pcall.
+lua_equal and lua_lessthan are deprecated.
+Use the new lua_compare with appropriate options instead.
+lua_objlen was renamed lua_rawlen.
+lua_load has an extra parameter, mode.
+Pass NULL to simulate the old behavior.
+lua_resume has an extra parameter, from.
+Pass NULL or the thread doing the call.
++Here is the complete syntax of Lua in extended BNF. +(It does not describe operator precedences.) + + + + +
+
+ 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 namelist [‘=’ explist]
+
+ 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 | Number | String | ‘...’ | functiondef |
+ prefixexp | tableconstructor | exp binop exp | unop exp
+
+ prefixexp ::= var | functioncall | ‘(’ exp ‘)’
+
+ functioncall ::= prefixexp args | prefixexp ‘:’ Name args
+
+ args ::= ‘(’ [explist] ‘)’ | tableconstructor | String
+
+ 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 | ‘#’
+
+
+
++ + + + + + + +