diff --git a/deps/CMakeLists.txt b/deps/CMakeLists.txt
index e3b91efc2568294caec0e2b8f7cb61d870bae5de..62c3b643c0ac42536da5f966f03ddde1569f6025 100644
--- a/deps/CMakeLists.txt
+++ b/deps/CMakeLists.txt
@@ -11,6 +11,10 @@ ADD_SUBDIRECTORY(wepoll)
ADD_SUBDIRECTORY(MsvcLibX)
ADD_SUBDIRECTORY(rmonotonic)
+IF (TD_LINUX_64)
+ ADD_SUBDIRECTORY(lua)
+ENDIF ()
+
IF (TD_LINUX AND TD_MQTT)
ADD_SUBDIRECTORY(MQTT-C)
ENDIF ()
diff --git a/deps/lua/CMakeLists.txt b/deps/lua/CMakeLists.txt
new file mode 100644
index 0000000000000000000000000000000000000000..8981350c3b419ff3c8611b0e2d72041ec179fd4d
--- /dev/null
+++ b/deps/lua/CMakeLists.txt
@@ -0,0 +1,4 @@
+AUX_SOURCE_DIRECTORY(${CMAKE_CURRENT_SOURCE_DIR}/src SOURCE_LIST)
+
+ADD_LIBRARY(lua ${SOURCE_LIST})
+TARGET_INCLUDE_DIRECTORIES(lua PUBLIC ${CMAKE_CURRENT_SOURCE_DIR}/inc)
diff --git a/deps/lua/COPYRIGHT b/deps/lua/COPYRIGHT
new file mode 100644
index 0000000000000000000000000000000000000000..84d401b1e4d1e8f952943df8a800f9383aa23fe1
--- /dev/null
+++ b/deps/lua/COPYRIGHT
@@ -0,0 +1,34 @@
+Lua License
+-----------
+
+Lua is licensed under the terms of the MIT license reproduced below.
+This means that Lua is free software and can be used for both academic
+and commercial purposes at absolutely no cost.
+
+For details and rationale, see http://www.lua.org/license.html .
+
+===============================================================================
+
+Copyright (C) 1994-2006 Lua.org, PUC-Rio.
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in
+all copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+THE SOFTWARE.
+
+===============================================================================
+
+(end of COPYRIGHT)
diff --git a/deps/lua/HISTORY b/deps/lua/HISTORY
new file mode 100644
index 0000000000000000000000000000000000000000..d807a533835a9f7c3976a97839dc9dca72e679d3
--- /dev/null
+++ b/deps/lua/HISTORY
@@ -0,0 +1,183 @@
+HISTORY for Lua 5.1
+
+* Changes from version 5.0 to 5.1
+ -------------------------------
+ Language:
+ + new module system.
+ + new semantics for control variables of fors.
+ + new semantics for setn/getn.
+ + new syntax/semantics for varargs.
+ + new long strings and comments.
+ + new `mod' operator (`%')
+ + new length operator #t
+ + metatables for all types
+ API:
+ + new functions: lua_createtable, lua_get(set)field, lua_push(to)integer.
+ + user supplies memory allocator (lua_open becomes lua_newstate).
+ + luaopen_* functionst must be called through Lua.
+ Implementation:
+ + new configuration scheme via luaconf.h.
+ + incremental garbage collection.
+ + better handling of end-of-line in the lexer.
+ + fully reentrant parser (new Lua function `load')
+ + better support for 64-bit machines.
+ + native loadlib support for Mac OS X.
+ + standard distribution in only one library (lualib.a merged into lua.a)
+
+* Changes from version 4.0 to 5.0
+ -------------------------------
+ Language:
+ + lexical scoping.
+ + Lua coroutines.
+ + standard libraries now packaged in tables.
+ + tags replaced by metatables and tag methods replaced by metamethods,
+ stored in metatables.
+ + proper tail calls.
+ + each function can have its own global table, which can be shared.
+ + new __newindex metamethod, called when we insert a new key into a table.
+ + new block comments: --[[ ... ]].
+ + new generic for.
+ + new weak tables.
+ + new boolean type.
+ + new syntax "local function".
+ + (f()) returns the first value returned by f.
+ + {f()} fills a table with all values returned by f.
+ + \n ignored in [[\n .
+ + fixed and-or priorities.
+ + more general syntax for function definition (e.g. function a.x.y:f()...end).
+ + more general syntax for function calls (e.g. (print or write)(9)).
+ + new functions (time/date, tmpfile, unpack, require, load*, etc.).
+ API:
+ + chunks are loaded by using lua_load; new luaL_loadfile and luaL_loadbuffer.
+ + introduced lightweight userdata, a simple "void*" without a metatable.
+ + new error handling protocol: the core no longer prints error messages;
+ all errors are reported to the caller on the stack.
+ + new lua_atpanic for host cleanup.
+ + new, signal-safe, hook scheme.
+ Implementation:
+ + new license: MIT.
+ + new, faster, register-based virtual machine.
+ + support for external multithreading and coroutines.
+ + new and consistent error message format.
+ + the core no longer needs "stdio.h" for anything (except for a single
+ use of sprintf to convert numbers to strings).
+ + lua.c now runs the environment variable LUA_INIT, if present. It can
+ be "@filename", to run a file, or the chunk itself.
+ + support for user extensions in lua.c.
+ sample implementation given for command line editing.
+ + new dynamic loading library, active by default on several platforms.
+ + safe garbage-collector metamethods.
+ + precompiled bytecodes checked for integrity (secure binary dostring).
+ + strings are fully aligned.
+ + position capture in string.find.
+ + read('*l') can read lines with embedded zeros.
+
+* Changes from version 3.2 to 4.0
+ -------------------------------
+ Language:
+ + new "break" and "for" statements (both numerical and for tables).
+ + uniform treatment of globals: globals are now stored in a Lua table.
+ + improved error messages.
+ + no more '$debug': full speed *and* full debug information.
+ + new read form: read(N) for next N bytes.
+ + general read patterns now deprecated.
+ (still available with -DCOMPAT_READPATTERNS.)
+ + all return values are passed as arguments for the last function
+ (old semantics still available with -DLUA_COMPAT_ARGRET)
+ + garbage collection tag methods for tables now deprecated.
+ + there is now only one tag method for order.
+ API:
+ + New API: fully re-entrant, simpler, and more efficient.
+ + New debug API.
+ Implementation:
+ + faster than ever: cleaner virtual machine and new hashing algorithm.
+ + non-recursive garbage-collector algorithm.
+ + reduced memory usage for programs with many strings.
+ + improved treatment for memory allocation errors.
+ + improved support for 16-bit machines (we hope).
+ + code now compiles unmodified as both ANSI C and C++.
+ + numbers in bases other than 10 are converted using strtoul.
+ + new -f option in Lua to support #! scripts.
+ + luac can now combine text and binaries.
+
+* Changes from version 3.1 to 3.2
+ -------------------------------
+ + redirected all output in Lua's core to _ERRORMESSAGE and _ALERT.
+ + increased limit on the number of constants and globals per function
+ (from 2^16 to 2^24).
+ + debugging info (lua_debug and hooks) moved into lua_state and new API
+ functions provided to get and set this info.
+ + new debug lib gives full debugging access within Lua.
+ + new table functions "foreachi", "sort", "tinsert", "tremove", "getn".
+ + new io functions "flush", "seek".
+
+* Changes from version 3.0 to 3.1
+ -------------------------------
+ + NEW FEATURE: anonymous functions with closures (via "upvalues").
+ + new syntax:
+ - local variables in chunks.
+ - better scope control with DO block END.
+ - constructors can now be also written: { record-part; list-part }.
+ - more general syntax for function calls and lvalues, e.g.:
+ f(x).y=1
+ o:f(x,y):g(z)
+ f"string" is sugar for f("string")
+ + strings may now contain arbitrary binary data (e.g., embedded zeros).
+ + major code re-organization and clean-up; reduced module interdependecies.
+ + no arbitrary limits on the total number of constants and globals.
+ + support for multiple global contexts.
+ + better syntax error messages.
+ + new traversal functions "foreach" and "foreachvar".
+ + the default for numbers is now double.
+ changing it to use floats or longs is easy.
+ + complete debug information stored in pre-compiled chunks.
+ + sample interpreter now prompts user when run interactively, and also
+ handles control-C interruptions gracefully.
+
+* Changes from version 2.5 to 3.0
+ -------------------------------
+ + NEW CONCEPT: "tag methods".
+ Tag methods replace fallbacks as the meta-mechanism for extending the
+ semantics of Lua. Whereas fallbacks had a global nature, tag methods
+ work on objects having the same tag (e.g., groups of tables).
+ Existing code that uses fallbacks should work without change.
+ + new, general syntax for constructors {[exp] = exp, ... }.
+ + support for handling variable number of arguments in functions (varargs).
+ + support for conditional compilation ($if ... $else ... $end).
+ + cleaner semantics in API simplifies host code.
+ + better support for writing libraries (auxlib.h).
+ + better type checking and error messages in the standard library.
+ + luac can now also undump.
+
+* Changes from version 2.4 to 2.5
+ -------------------------------
+ + io and string libraries are now based on pattern matching;
+ the old libraries are still available for compatibility
+ + dofile and dostring can now return values (via return statement)
+ + better support for 16- and 64-bit machines
+ + expanded documentation, with more examples
+
+* Changes from version 2.2 to 2.4
+ -------------------------------
+ + external compiler creates portable binary files that can be loaded faster
+ + interface for debugging and profiling
+ + new "getglobal" fallback
+ + new functions for handling references to Lua objects
+ + new functions in standard lib
+ + only one copy of each string is stored
+ + expanded documentation, with more examples
+
+* Changes from version 2.1 to 2.2
+ -------------------------------
+ + functions now may be declared with any "lvalue" as a name
+ + garbage collection of functions
+ + support for pipes
+
+* Changes from version 1.1 to 2.1
+ -------------------------------
+ + object-oriented support
+ + fallbacks
+ + simplified syntax for tables
+ + many internal improvements
+
+(end of HISTORY)
diff --git a/deps/lua/INSTALL b/deps/lua/INSTALL
new file mode 100644
index 0000000000000000000000000000000000000000..65f6f1eb07bf3e62fc0fbffd70a970827eb138bc
--- /dev/null
+++ b/deps/lua/INSTALL
@@ -0,0 +1,96 @@
+INSTALL for Lua 5.1
+
+* Building Lua
+ ------------
+ Lua is built in the src directory, but the build process can be
+ controlled from the top-level Makefile.
+
+ Building Lua on Unix systems should be very easy. First do "make" and
+ see if your platform is listed. If so, just do "make xxx", where xxx
+ is your platform name. The platforms currently supported are:
+ ansi bsd generic linux macosx mingw posix solaris
+
+ See below for customization instructions and for instructions on how
+ to build with other Windows compilers.
+
+ If you want to check that Lua has been built correctly, do "make test"
+ after building Lua. Also, have a look at the example programs in test.
+
+* Installing Lua
+ --------------
+ Once you have built Lua, you may want to install it in an official
+ place in your system. In this case, do "make install". The official
+ place and the way to install files are defined in Makefile. You must
+ have the right permissions to install files.
+
+ If you want to build and install Lua in one step, do "make xxx install",
+ where xxx is your platform name.
+
+ If you want to install Lua locally, then do "make local". This will
+ create directories bin, include, lib, man, and install Lua there as
+ follows:
+
+ bin: lua luac
+ include: lua.h luaconf.h lualib.h lauxlib.h lua.hpp
+ lib: liblua.a
+ man/man1: lua.1 luac.1
+
+ These are the only directories you need for development.
+
+ There are man pages for lua and luac, in both nroff and html, and a
+ reference manual in html in doc, some sample code in test, and some
+ useful stuff in etc. You don't need these directories for development.
+
+ If you want to install Lua locally, but in some other directory, do
+ "make install INSTALL_TOP=xxx", where xxx is your chosen directory.
+
+ See below for instructions for Windows and other systems.
+
+* Customization
+ -------------
+ Three things can be customized by editing a file:
+ - Where and how to install Lua -- edit Makefile.
+ - How to build Lua -- edit src/Makefile.
+ - Lua features -- edit src/luaconf.h.
+
+ You don't actually need to edit the Makefiles because you may set the
+ relevant variables when invoking make.
+
+ On the other hand, if you need to select some Lua features, you'll need
+ to edit src/luaconf.h. The edited file will be the one installed, and
+ it will be used by any Lua clients that you build, to ensure consistency.
+
+ We strongly recommend that you enable dynamic loading. This is done
+ automatically for all platforms listed above that have this feature
+ (and also Windows). See src/luaconf.h and also src/Makefile.
+
+* Building Lua on Windows and other systems
+ -----------------------------------------
+ If you're not using the usual Unix tools, then the instructions for
+ building Lua depend on the compiler you use. You'll need to create
+ projects (or whatever your compiler uses) for building the library,
+ the interpreter, and the compiler, as follows:
+
+ library: lapi.c lcode.c ldebug.c ldo.c ldump.c lfunc.c lgc.c llex.c
+ lmem.c lobject.c lopcodes.c lparser.c lstate.c lstring.c
+ ltable.c ltm.c lundump.c lvm.c lzio.c
+ lauxlib.c lbaselib.c ldblib.c liolib.c lmathlib.c loslib.c
+ ltablib.c lstrlib.c loadlib.c linit.c
+
+ interpreter: library, lua.c
+
+ compiler: library, luac.c print.c
+
+ If you use Visual Studio .NET, you can use etc/luavs.bat
+ in its "Command Prompt".
+
+ If all you want is to build the Lua interpreter, you may put all .c files
+ in a single project, except for luac.c and print.c. Or just use etc/all.c.
+
+ To use Lua as a library in your own programs, you'll need to know how to
+ create and use libraries with your compiler.
+
+ As mentioned above, you may edit luaconf.h to select some features before
+ building Lua.
+
+(end of INSTALL)
diff --git a/deps/lua/MANIFEST b/deps/lua/MANIFEST
new file mode 100644
index 0000000000000000000000000000000000000000..fd18c8bb9e3acbcabf2c4a5e5c8c2158c94c1635
--- /dev/null
+++ b/deps/lua/MANIFEST
@@ -0,0 +1,108 @@
+MANIFEST contents of Lua 5.1 distribution on Mon Feb 20 11:37:30 BRT 2006
+lua-5.1
+lua-5.1/COPYRIGHT
+lua-5.1/HISTORY
+lua-5.1/INSTALL
+lua-5.1/MANIFEST
+lua-5.1/Makefile
+lua-5.1/README
+lua-5.1/doc
+lua-5.1/doc/contents.html
+lua-5.1/doc/logo.gif
+lua-5.1/doc/lua.1
+lua-5.1/doc/lua.css
+lua-5.1/doc/lua.html
+lua-5.1/doc/luac.1
+lua-5.1/doc/luac.html
+lua-5.1/doc/manual.html
+lua-5.1/doc/readme.html
+lua-5.1/etc
+lua-5.1/etc/Makefile
+lua-5.1/etc/README
+lua-5.1/etc/all.c
+lua-5.1/etc/lua.hpp
+lua-5.1/etc/lua.ico
+lua-5.1/etc/lua.pc
+lua-5.1/etc/luavs.bat
+lua-5.1/etc/min.c
+lua-5.1/etc/noparser.c
+lua-5.1/etc/strict.lua
+lua-5.1/src
+lua-5.1/src/Makefile
+lua-5.1/src/lapi.c
+lua-5.1/src/lapi.h
+lua-5.1/src/lauxlib.c
+lua-5.1/src/lauxlib.h
+lua-5.1/src/lbaselib.c
+lua-5.1/src/lcode.c
+lua-5.1/src/lcode.h
+lua-5.1/src/ldblib.c
+lua-5.1/src/ldebug.c
+lua-5.1/src/ldebug.h
+lua-5.1/src/ldo.c
+lua-5.1/src/ldo.h
+lua-5.1/src/ldump.c
+lua-5.1/src/lfunc.c
+lua-5.1/src/lfunc.h
+lua-5.1/src/lgc.c
+lua-5.1/src/lgc.h
+lua-5.1/src/linit.c
+lua-5.1/src/liolib.c
+lua-5.1/src/llex.c
+lua-5.1/src/llex.h
+lua-5.1/src/llimits.h
+lua-5.1/src/lmathlib.c
+lua-5.1/src/lmem.c
+lua-5.1/src/lmem.h
+lua-5.1/src/loadlib.c
+lua-5.1/src/lobject.c
+lua-5.1/src/lobject.h
+lua-5.1/src/lopcodes.c
+lua-5.1/src/lopcodes.h
+lua-5.1/src/loslib.c
+lua-5.1/src/lparser.c
+lua-5.1/src/lparser.h
+lua-5.1/src/lstate.c
+lua-5.1/src/lstate.h
+lua-5.1/src/lstring.c
+lua-5.1/src/lstring.h
+lua-5.1/src/lstrlib.c
+lua-5.1/src/ltable.c
+lua-5.1/src/ltable.h
+lua-5.1/src/ltablib.c
+lua-5.1/src/ltm.c
+lua-5.1/src/ltm.h
+lua-5.1/src/lua.c
+lua-5.1/src/lua.h
+lua-5.1/src/luac.c
+lua-5.1/src/luaconf.h
+lua-5.1/src/lualib.h
+lua-5.1/src/lundump.c
+lua-5.1/src/lundump.h
+lua-5.1/src/lvm.c
+lua-5.1/src/lvm.h
+lua-5.1/src/lzio.c
+lua-5.1/src/lzio.h
+lua-5.1/src/print.c
+lua-5.1/test
+lua-5.1/test/README
+lua-5.1/test/bisect.lua
+lua-5.1/test/cf.lua
+lua-5.1/test/echo.lua
+lua-5.1/test/env.lua
+lua-5.1/test/factorial.lua
+lua-5.1/test/fib.lua
+lua-5.1/test/fibfor.lua
+lua-5.1/test/globals.lua
+lua-5.1/test/hello.lua
+lua-5.1/test/life.lua
+lua-5.1/test/luac.lua
+lua-5.1/test/printf.lua
+lua-5.1/test/readonly.lua
+lua-5.1/test/sieve.lua
+lua-5.1/test/sort.lua
+lua-5.1/test/table.lua
+lua-5.1/test/trace-calls.lua
+lua-5.1/test/trace-globals.lua
+lua-5.1/test/xd.lua
+END OF MANIFEST
diff --git a/deps/lua/README b/deps/lua/README
new file mode 100644
index 0000000000000000000000000000000000000000..f082d4046091b1a54c1b7dea41c8db04d8c21b2b
--- /dev/null
+++ b/deps/lua/README
@@ -0,0 +1,37 @@
+README for Lua 5.1
+
+See INSTALL for installation instructions.
+See HISTORY for a summary of changes since the last released version.
+
+* What is Lua?
+ ------------
+ Lua is a powerful, light-weight programming language designed for extending
+ applications. Lua is also frequently used as a general-purpose, stand-alone
+ language. Lua is free software.
+
+ For complete information, visit Lua's web site at http://www.lua.org/ .
+ For an executive summary, see http://www.lua.org/about.html .
+
+ Lua has been used in many different projects around the world.
+ For a short list, see http://www.lua.org/uses.html .
+
+* Availability
+ ------------
+ Lua is freely available for both academic and commercial purposes.
+ See COPYRIGHT and http://www.lua.org/license.html for details.
+ Lua can be downloaded at http://www.lua.org/download.html .
+
+* Installation
+ ------------
+ Lua is implemented in pure ANSI C, and compiles unmodified in all known
+ platforms that have an ANSI C compiler. Under Unix, simply typing "make"
+ should work. See INSTALL for detailed instructions.
+
+* Origin
+ ------
+ Lua is developed at Lua.org, a laboratory of the Department of Computer
+ Science of PUC-Rio (the Pontifical Catholic University of Rio de Janeiro
+ in Brazil).
+ For more information about the authors, see http://www.lua.org/authors.html .
+
+(end of README)
diff --git a/deps/lua/doc/contents.html b/deps/lua/doc/contents.html
new file mode 100644
index 0000000000000000000000000000000000000000..564377c942a1e5e0c0a76c85bbde344c5cca450d
--- /dev/null
+++ b/deps/lua/doc/contents.html
@@ -0,0 +1,405 @@
+
+
+Lua 5.1 reference manual - contents
+
+
+
+
+
+
+
+
+Last update:
+Fri Feb 10 17:15:37 BRST 2006
+
+
+
+
diff --git a/deps/lua/doc/logo.gif b/deps/lua/doc/logo.gif
new file mode 100644
index 0000000000000000000000000000000000000000..2f5e4ac2e742fbb7675e739879211553758aea9c
Binary files /dev/null and b/deps/lua/doc/logo.gif differ
diff --git a/deps/lua/doc/lua.1 b/deps/lua/doc/lua.1
new file mode 100644
index 0000000000000000000000000000000000000000..24809cc6c10e47660e09f5d0129795dc8c870404
--- /dev/null
+++ b/deps/lua/doc/lua.1
@@ -0,0 +1,163 @@
+.\" $Id: lua.man,v 1.11 2006/01/06 16:03:34 lhf Exp $
+.TH LUA 1 "$Date: 2006/01/06 16:03:34 $"
+.SH NAME
+lua \- Lua interpreter
+.SH SYNOPSIS
+.B lua
+[
+.I options
+]
+[
+.I script
+[
+.I args
+]
+]
+.SH DESCRIPTION
+.B lua
+is the stand-alone Lua interpreter.
+It loads and executes Lua programs,
+either in textual source form or
+in precompiled binary form.
+(Precompiled binaries are output by
+.BR luac ,
+the Lua compiler.)
+.B lua
+can be used as a batch interpreter and also interactively.
+.LP
+The given
+.I options
+(see below)
+are executed and then
+the Lua program in file
+.I script
+is loaded and executed.
+The given
+.I args
+are available to
+.I script
+as strings in a global table named
+.BR arg .
+If these arguments contain spaces or other characters special to the shell,
+then they should be quoted
+(but note that the quotes will be removed by the shell).
+The arguments in
+.B arg
+start at 0,
+which contains the string
+.RI ' script '.
+The index of the last argument is stored in
+.BR arg.n .
+The arguments given in the command line before
+.IR script ,
+including the name of the interpreter,
+are available in negative indices in
+.BR arg .
+.LP
+At the very start,
+before even handling the command line,
+.B lua
+executes the contents of the environment variable
+.BR LUA_INIT ,
+if it is defined.
+If the value of
+.B LUA_INIT
+is of the form
+.RI '@ filename ',
+then
+.I filename
+is executed.
+Otherwise, the string is assumed to be a Lua statement and is executed.
+.LP
+Options start with
+.B '\-'
+and are described below.
+You can use
+.B "'\--'"
+to signal the end of options.
+.LP
+If no arguments are given,
+then
+.B "\-v \-i"
+is assumed when the standard input is a terminal;
+otherwise,
+.B "\-"
+is assumed.
+.LP
+In interactive mode,
+.B lua
+prompts the user,
+reads lines from the standard input,
+and executes them as they are read.
+If a line does not contain a complete statement,
+then a secondary prompt is displayed and
+lines are read until a complete statement is formed or
+a syntax error is found.
+So, one way to interrupt the reading of an incomplete statement is
+to force a syntax error:
+adding a
+.B ';'
+in the middle of a statement is a sure way of forcing a syntax error
+(except inside multiline strings and comments; these must be closed explicitly).
+If a line starts with
+.BR '=' ,
+then
+.B lua
+displays the values of all the expressions in the remainder of the
+line. The expressions must be separated by commas.
+The primary prompt is the value of the global variable
+.BR _PROMPT ,
+if this value is a string;
+otherwise, the default prompt is used.
+Similarly, the secondary prompt is the value of the global variable
+.BR _PROMPT2 .
+So,
+to change the prompts,
+set the corresponding variable to a string of your choice.
+You can do that after calling the interpreter
+or on the command line
+(but in this case you have to be careful with quotes
+if the prompt string contains a space; otherwise you may confuse the shell.)
+The default prompts are "> " and ">> ".
+.SH OPTIONS
+.TP
+.B \-
+load and execute the standard input as a file,
+that is,
+not interactively,
+even when the standard input is a terminal.
+.TP
+.BI \-e " stat"
+execute statement
+.IR stat .
+You need to quote
+.I stat
+if it contains spaces, quotes,
+or other characters special to the shell.
+.TP
+.B \-i
+enter interactive mode after
+.I script
+is executed.
+.TP
+.BI \-l " name"
+call
+.BI require(' name ')
+before executing
+.IR script .
+Typically used to load libraries.
+.TP
+.B \-v
+show version information.
+.SH "SEE ALSO"
+.BR luac (1)
+.br
+http://www.lua.org/
+.SH DIAGNOSTICS
+Error messages should be self explanatory.
+.SH AUTHORS
+R. Ierusalimschy,
+L. H. de Figueiredo,
+and
+W. Celes
+.\" EOF
diff --git a/deps/lua/doc/lua.css b/deps/lua/doc/lua.css
new file mode 100644
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--- /dev/null
+++ b/deps/lua/doc/lua.css
@@ -0,0 +1,15 @@
+body {
+ color: #000000 ;
+ background-color: #FFFFFF ;
+ font-family: sans-serif ;
+}
+
+a:link {
+ color: #000080 ;
+}
+
+a:link:hover, a:visited:hover {
+ color: #000080 ;
+ background-color: #E0E0FF ;
+}
+
diff --git a/deps/lua/doc/lua.html b/deps/lua/doc/lua.html
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--- /dev/null
+++ b/deps/lua/doc/lua.html
@@ -0,0 +1,172 @@
+
+
+
+LUA man page
+
+
+
+
+
+
NAME
+lua - Lua interpreter
+
SYNOPSIS
+lua
+[
+options
+]
+[
+script
+[
+args
+]
+]
+
DESCRIPTION
+lua
+is the stand-alone Lua interpreter.
+It loads and executes Lua programs,
+either in textual source form or
+in precompiled binary form.
+(Precompiled binaries are output by
+luac,
+the Lua compiler.)
+lua
+can be used as a batch interpreter and also interactively.
+
+The given
+options
+(see below)
+are executed and then
+the Lua program in file
+script
+is loaded and executed.
+The given
+args
+are available to
+script
+as strings in a global table named
+arg.
+If these arguments contain spaces or other characters special to the shell,
+then they should be quoted
+(but note that the quotes will be removed by the shell).
+The arguments in
+arg
+start at 0,
+which contains the string
+'script'.
+The index of the last argument is stored in
+arg.n.
+The arguments given in the command line before
+script,
+including the name of the interpreter,
+are available in negative indices in
+arg.
+
+At the very start,
+before even handling the command line,
+lua
+executes the contents of the environment variable
+LUA_INIT,
+if it is defined.
+If the value of
+LUA_INIT
+is of the form
+'@filename',
+then
+filename
+is executed.
+Otherwise, the string is assumed to be a Lua statement and is executed.
+
+Options start with
+'-'
+and are described below.
+You can use
+'--'
+to signal the end of options.
+
+If no arguments are given,
+then
+"-v -i"
+is assumed when the standard input is a terminal;
+otherwise,
+"-"
+is assumed.
+
+In interactive mode,
+lua
+prompts the user,
+reads lines from the standard input,
+and executes them as they are read.
+If a line does not contain a complete statement,
+then a secondary prompt is displayed and
+lines are read until a complete statement is formed or
+a syntax error is found.
+So, one way to interrupt the reading of an incomplete statement is
+to force a syntax error:
+adding a
+';'
+in the middle of a statement is a sure way of forcing a syntax error
+(except inside multiline strings and comments; these must be closed explicitly).
+If a line starts with
+'=',
+then
+lua
+displays the values of all the expressions in the remainder of the
+line. The expressions must be separated by commas.
+The primary prompt is the value of the global variable
+_PROMPT,
+if this value is a string;
+otherwise, the default prompt is used.
+Similarly, the secondary prompt is the value of the global variable
+_PROMPT2.
+So,
+to change the prompts,
+set the corresponding variable to a string of your choice.
+You can do that after calling the interpreter
+or on the command line
+(but in this case you have to be careful with quotes
+if the prompt string contains a space; otherwise you may confuse the shell.)
+The default prompts are "> " and ">> ".
+
OPTIONS
+
+-
+load and execute the standard input as a file,
+that is,
+not interactively,
+even when the standard input is a terminal.
+
+-e stat
+execute statement
+stat.
+You need to quote
+stat
+if it contains spaces, quotes,
+or other characters special to the shell.
+
+-i
+enter interactive mode after
+script
+is executed.
+
+-l name
+call
+require('name')
+before executing
+script.
+Typically used to load libraries.
+
+R. Ierusalimschy,
+L. H. de Figueiredo,
+and
+W. Celes
+
+
+
diff --git a/deps/lua/doc/luac.1 b/deps/lua/doc/luac.1
new file mode 100644
index 0000000000000000000000000000000000000000..d8146782df78a432f0da341b11da0e72e6cec31d
--- /dev/null
+++ b/deps/lua/doc/luac.1
@@ -0,0 +1,136 @@
+.\" $Id: luac.man,v 1.28 2006/01/06 16:03:34 lhf Exp $
+.TH LUAC 1 "$Date: 2006/01/06 16:03:34 $"
+.SH NAME
+luac \- Lua compiler
+.SH SYNOPSIS
+.B luac
+[
+.I options
+] [
+.I filenames
+]
+.SH DESCRIPTION
+.B luac
+is the Lua compiler.
+It translates programs written in the Lua programming language
+into binary files that can be later loaded and executed.
+.LP
+The main advantages of precompiling chunks are:
+faster loading,
+protecting source code from accidental user changes,
+and
+off-line syntax checking.
+.LP
+Pre-compiling does not imply faster execution
+because in Lua chunks are always compiled into bytecodes before being executed.
+.B luac
+simply allows those bytecodes to be saved in a file for later execution.
+.LP
+Pre-compiled chunks are not necessarily smaller than the corresponding source.
+The main goal in pre-compiling is faster loading.
+.LP
+The binary files created by
+.B luac
+are portable only among architectures with the same word size and byte order.
+.LP
+.B luac
+produces a single output file containing the bytecodes
+for all source files given.
+By default,
+the output file is named
+.BR luac.out ,
+but you can change this with the
+.B \-o
+option.
+.LP
+In the command line,
+you can mix
+text files containing Lua source and
+binary files containing precompiled chunks.
+This is useful to combine several precompiled chunks,
+even from different (but compatible) platforms,
+into a single precompiled chunk.
+.LP
+You can use
+.B "'\-'"
+to indicate the standard input as a source file
+and
+.B "'\--'"
+to signal the end of options
+(that is,
+all remaining arguments will be treated as files even if they start with
+.BR "'\-'" ).
+.LP
+The internal format of the binary files produced by
+.B luac
+is likely to change when a new version of Lua is released.
+So,
+save the source files of all Lua programs that you precompile.
+.LP
+.SH OPTIONS
+Options must be separate.
+.TP
+.B \-l
+produce a listing of the compiled bytecode for Lua's virtual machine.
+Listing bytecodes is useful to learn about Lua's virtual machine.
+If no files are given, then
+.B luac
+loads
+.B luac.out
+and lists its contents.
+.TP
+.BI \-o " file"
+output to
+.IR file ,
+instead of the default
+.BR luac.out .
+(You can use
+.B "'\-'"
+for standard output,
+but not on platforms that open standard output in text mode.)
+The output file may be a source file because
+all files are loaded before the output file is written.
+Be careful not to overwrite precious files.
+.TP
+.B \-p
+load files but do not generate any output file.
+Used mainly for syntax checking and for testing precompiled chunks:
+corrupted files will probably generate errors when loaded.
+Lua always performs a thorough integrity test on precompiled chunks.
+Bytecode that passes this test is completely safe,
+in the sense that it will not break the interpreter.
+However,
+there is no guarantee that such code does anything sensible.
+(None can be given, because the halting problem is unsolvable.)
+If no files are given, then
+.B luac
+loads
+.B luac.out
+and tests its contents.
+No messages are displayed if the file passes the integrity test.
+.TP
+.B \-s
+strip debug information before writing the output file.
+This saves some space in very large chunks,
+but if errors occur when running a stripped chunk,
+then the error messages may not contain the full information they usually do.
+For instance,
+line numbers and names of local variables are lost.
+.TP
+.B \-v
+show version information.
+.SH FILES
+.TP 15
+.B luac.out
+default output file
+.SH "SEE ALSO"
+.BR lua (1)
+.br
+http://www.lua.org/
+.SH DIAGNOSTICS
+Error messages should be self explanatory.
+.SH AUTHORS
+L. H. de Figueiredo,
+R. Ierusalimschy and
+W. Celes
+.\" EOF
diff --git a/deps/lua/doc/luac.html b/deps/lua/doc/luac.html
new file mode 100644
index 0000000000000000000000000000000000000000..179ffe82886cb900e11105b28a3040f0e2778c1f
--- /dev/null
+++ b/deps/lua/doc/luac.html
@@ -0,0 +1,145 @@
+
+
+
+LUAC man page
+
+
+
+
+
+
NAME
+luac - Lua compiler
+
SYNOPSIS
+luac
+[
+options
+] [
+filenames
+]
+
DESCRIPTION
+luac
+is the Lua compiler.
+It translates programs written in the Lua programming language
+into binary files that can be later loaded and executed.
+
+The main advantages of precompiling chunks are:
+faster loading,
+protecting source code from accidental user changes,
+and
+off-line syntax checking.
+
+Precompiling does not imply faster execution
+because in Lua chunks are always compiled into bytecodes before being executed.
+luac
+simply allows those bytecodes to be saved in a file for later execution.
+
+Precompiled chunks are not necessarily smaller than the corresponding source.
+The main goal in precompiling is faster loading.
+
+The binary files created by
+luac
+are portable only among architectures with the same word size and byte order.
+
+luac
+produces a single output file containing the bytecodes
+for all source files given.
+By default,
+the output file is named
+luac.out,
+but you can change this with the
+-o
+option.
+
+In the command line,
+you can mix
+text files containing Lua source and
+binary files containing precompiled chunks.
+This is useful because several precompiled chunks,
+even from different (but compatible) platforms,
+can be combined into a single precompiled chunk.
+
+You can use
+'-'
+to indicate the standard input as a source file
+and
+'--'
+to signal the end of options
+(that is,
+all remaining arguments will be treated as files even if they start with
+'-').
+
+The internal format of the binary files produced by
+luac
+is likely to change when a new version of Lua is released.
+So,
+save the source files of all Lua programs that you precompile.
+
+
OPTIONS
+Options must be separate.
+
+-l
+produce a listing of the compiled bytecode for Lua's virtual machine.
+Listing bytecodes is useful to learn about Lua's virtual machine.
+If no files are given, then
+luac
+loads
+luac.out
+and lists its contents.
+
+-o file
+output to
+file,
+instead of the default
+luac.out.
+(You can use
+'-'
+for standard output,
+but not on platforms that open standard output in text mode.)
+The output file may be a source file because
+all files are loaded before the output file is written.
+Be careful not to overwrite precious files.
+
+-p
+load files but do not generate any output file.
+Used mainly for syntax checking and for testing precompiled chunks:
+corrupted files will probably generate errors when loaded.
+Lua always performs a thorough integrity test on precompiled chunks.
+Bytecode that passes this test is completely safe,
+in the sense that it will not break the interpreter.
+However,
+there is no guarantee that such code does anything sensible.
+(None can be given, because the halting problem is unsolvable.)
+If no files are given, then
+luac
+loads
+luac.out
+and tests its contents.
+No messages are displayed if the file passes the integrity test.
+
+-s
+strip debug information before writing the output file.
+This saves some space in very large chunks,
+but if errors occur when running a stripped chunk,
+then the error messages may not contain the full information they usually do.
+For instance,
+line numbers and names of local variables are lost.
+
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, light-weight
+scripting language for any program that needs one.
+Lua is implemented as a library, written in clean C
+(that is, in the common subset of ANSI 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.
+This 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, stand-alone Lua interpreter.
+
+
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.
+
+
+
2 - The Language
+
+
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.
+
+
The 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 in italics,
+keywords are shown in bold,
+and other terminal symbols are shown in typewriter font,
+enclosed in single quotes.
+The complete syntax of Lua can be found at the end of this manual.
+
+
2.1 - Lexical Conventions
+
+
Names
+(also called identifiers)
+in Lua can be any string of letters,
+digits, and underscores,
+not beginning with a digit.
+This coincides with the definition of names in most languages.
+(The definition of letter depends on the current locale:
+any character considered alphabetic by the current locale
+can be used in an identifier.)
+Identifiers are used to name variables and table fields.
+
+
The following keywords are reserved
+and cannot be used as names:
+
+
+ and break do else elseif
+ end false for function 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 internal global variables used by Lua.
+
+
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)
+
\' --- apostrophe (single quote)
+
+Moreover, a `\newline´
+(that is, a backslash followed by a real newline)
+results in a newline in the string.
+A character in a string may also be specified by its numerical value
+using the escape sequence `\ddd´,
+where ddd is a sequence of up to three decimal digits.
+(Note that if a numerical escape is to be followed by a digit,
+it must be expressed using exactly three digits.)
+Strings in Lua may contain any 8-bit value, including embedded zeros,
+which can be specified as `\0´.
+
+
To put a double (single) quote, a newline, a backslash,
+or an embedded zero
+inside a literal string enclosed by double (single) quotes
+you must use an escape sequence.
+Any other character may be directly inserted into the literal.
+(Some control characters may cause problems for the file system,
+but Lua has no problem with them.)
+
+
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 string starts with an opening long bracket of any level and
+ends at the first closing long bracket of the same level.
+Literals in this bracketed form may run for several lines,
+do not interpret any escape sequences,
+and ignore long brackets of any other level.
+They may contain anything except a closing bracket of the proper level
+or embedded zeros.
+
+
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 four literals below denote the same string:
+
Numerical constants may be written with an optional decimal part
+and an optional decimal exponent.
+Lua also accepts integer hexadecimal constants,
+by prefixing them with 0x.
+Examples of valid numerical constants are
+
+ 3 3.0 3.1416 314.16e-2 0.31416E1 0xff 0x56
+
+
+
Comments start 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.
+
+
2.2 - Values and Types
+
+
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.
+(It is easy to build Lua interpreters that use other
+internal representations for numbers,
+such as single-precision float or long integers.
+See file luaconf.h.)
+String represents arrays of characters.
+
+Lua is 8-bit clean:
+Strings may contain any 8-bit character,
+including embedded zeros (`\0´) (see 2.1).
+
+
Lua can call (and manipulate) functions written in Lua and
+functions written in C
+(see 2.5.8).
+
+
The type userdata is provided to allow arbitrary C data to
+be stored in Lua variables.
+This type corresponds to a block of raw memory
+and has no pre-defined operations in Lua,
+except assignment and identity test.
+However, by using metatables,
+the programmer can define operations for userdata values
+(see 2.8).
+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 2.11).
+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 value (except nil).
+Tables can be heterogeneous;
+that is, they can contain values of all types (except nil).
+Tables are the sole data structuring mechanism in Lua;
+they may be used to represent ordinary arrays,
+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 2.5.7).
+
+
Like indices,
+the value of a table field can be of any type (except nil).
+In particular,
+because functions are first-class values,
+table fields may contain functions.
+Thus tables may also carry methods (see 2.5.9).
+
+
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.
+
+
2.2.1 - Coercion
+
+
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 usual conversion rules.
+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).
+
+
2.3 - Variables
+
+
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 (see 2.1).
+
+
Variables are assumed to be global unless explicitly declared local
+(see 2.4.7).
+Local variables are lexically scoped:
+Local variables can be freely accessed by functions
+defined inside their scope (see 2.6).
+
+
Before the first assignment to a variable, its value is nil.
+
+
Square brackets are used to index a table:
+
+ var ::= prefixexp `[´ exp `]´
+
+The first expression (prefixexp) should result in a table value;
+the second expression (exp)
+identifies a specific entry in this table.
+The expression denoting the table to be indexed has a restricted syntax;
+see 2.5 for details.
+
+
The syntax var.Name is just syntactic sugar for
+var["Name"] and is used to denote table fields:
+
+ var ::= prefixexp `.´ Name
+
+
+
The meaning of accesses to global variables
+and 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 2.8 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.)
+
+
All global variables live as fields in ordinary Lua tables,
+called environment tables or simply
+environments (see 2.9).
+Each function has its own reference to an environment,
+so that all global variables in this function
+will refer to this environment table.
+When a function is created,
+it inherits the environment from the function that created it.
+To get the environment table of a Lua function,
+you call getfenv.
+To replace it,
+you call setfenv.
+(You can only manipulate the environment of C functions
+through the debug library; (see 5.9).)
+
+
An access to a global variable x
+is equivalent to _env.x,
+which in turn is equivalent to
+
+ gettable_event(_env, "x")
+
+where _env is the environment of the running function.
+(See 2.8 for a complete description of the
+gettable_event function.
+This function is not defined or callable in Lua.
+Similarly, the _env variable is not defined in Lua.
+We use them here only for explanatory purposes.)
+
+
2.4 - Statements
+
+
Lua supports an almost conventional set of statements,
+similar to those in Pascal or C.
+This set includes
+assignment, control structures, function calls,
+table constructors, and variable declarations.
+
+
2.4.1 - Chunks
+
+
The unit of execution of Lua is called a chunk.
+A chunk is simply a sequence of statements,
+which are executed sequentially.
+Each statement can be optionally followed by a semicolon:
+
+ chunk ::= {stat [`;´]}
+
+There are no empty statements and thus `;;´ is not legal.
+
+
Lua handles a chunk as the body of an anonymous function
+with a variable number of arguments
+(see 2.5.9).
+As such, chunks can define local variables,
+receive arguments, and return values.
+
+
A chunk may be stored in a file or in a string inside the host program.
+When a chunk is executed, first it is pre-compiled into instructions for
+a virtual machine,
+and then the compiled code is executed
+by an interpreter for the virtual machine.
+
+
Chunks may also be pre-compiled 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.
+
+
+
2.4.2 - Blocks
+A block is a list of statements;
+syntactically, a block is the same as a chunk:
+
+ block ::= chunk
+
+
+
A block may 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 or break statement in the middle
+of another block (see 2.4.4).
+
+
+
2.4.3 - Assignment
+
+
Lua allows multiple assignment.
+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 ::= varlist1 `=´ explist1
+ varlist1 ::= var {`,´ var}
+ explist1 ::= exp {`,´ exp}
+
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 this call enter in the list of values,
+before the adjustment
+(except when the call is enclosed in parentheses; see 2.5).
+
+
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.
+
+
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 2.8 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,
+which in turn is equivalent to
+
+ settable_event(_env, "x", val)
+
+where _env is the environment of the running function.
+(The _env variable is not defined in Lua.
+We use it here only for explanatory purposes.)
+
+
2.4.4 - Control Structures
+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 2.4.5).
+
+
The condition expression of a
+control structure may 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 return statement is used to return values
+from a function or a chunk (which is just a function).
+
+Functions and chunks may return more than one value,
+so the syntax for the return statement is
+
+ stat ::= return [explist1]
+
+
+
The break statement is used to terminate 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 and break
+statements can only be written as the last statement of a block.
+If it is really necessary to return or break in the
+middle of a block,
+then an explicit inner block can be used,
+as in the idioms
+`do return end´ and
+`do break end´,
+because now return and break are the last statements in
+their (inner) blocks.
+
+
2.4.5 - For Statement
+
+
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 var = 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 var = _var
+ block
+ _var = _var + _step
+ end
+ end
+
+Note the following:
+
+
All three control expressions are evaluated only once,
+before the loop starts.
+They must all result in numbers.
+
_var, _limit, and _step are invisible variables.
+The names are here for explanatory purposes only.
+
If the third expression (the step) is absent,
+then a step of 1 is used.
+
You can use break to exit a for loop.
+
The loop variable var is local to the loop;
+you cannot use its value after the for ends or is broken.
+If you need the value of the loop variable var,
+then 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 explist1 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)
+ _var = var_1
+ if _var == nil then break end
+ 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.
+
You can use break to exit a for loop.
+
The loop variables 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.
+
+
+
2.4.6 - Function Calls as Statements
+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 2.5.8.
+
+
2.4.7 - Local Declarations
+Local variables may be declared anywhere inside a block.
+The declaration may include an initial assignment:
+
+ stat ::= local namelist [`=´ explist1]
+
+If present, an initial assignment has the same semantics
+of a multiple assignment (see 2.4.3).
+Otherwise, all variables are initialized with nil.
+
+
A chunk is also a block (see 2.4.1),
+and so local variables can be declared in a chunk outside any explicit block.
+The scope of such local variables extends until the end of the chunk.
+
+
The visibility rules for local variables are explained in 2.6.
+
+
2.5 - Expressions
+
+
+The basic expressions in Lua are the following:
+
Numbers and literal strings are explained in 2.1;
+variables are explained in 2.3;
+function definitions are explained in 2.5.9;
+function calls are explained in 2.5.8;
+table constructors are explained in 2.5.7.
+Vararg expressions,
+denoted by three dots (`...´), can only be used inside
+vararg functions;
+they are explained in 2.5.9.
+
+
+
Binary operators comprise arithmetic operators (see 2.5.1),
+relational operators (see 2.5.2), and logical operators (see 2.5.3).
+Unary operators comprise the unary minus (see 2.5.1),
+the unary not (see 2.5.3),
+and the unary length operator (see 2.5.5).
+
+
Both function calls and vararg expressions may result in multiple values.
+If the expression is used as a statement (see 2.4.6)
+(only possible for function calls),
+then its return list is adjusted to zero elements,
+thus discarding all returned values.
+If the expression is used inside another expression
+or in the middle of a list of expressions,
+then its result list is adjusted to one element,
+thus discarding all values except the first one.
+If the expression is used as the last element of a list of expressions,
+then no adjustment is made,
+unless the call is enclosed in parentheses.
+
+
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 values returned by 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 may 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 values returned by f()
+ return ... -- returns all received vararg parameters
+ return x,y,f() -- returns x, y, and all values returned by f()
+ {f()} -- creates a list with all values returned by f()
+ {...} -- creates a list with all vararg parameters
+ {f(), nil} -- f() is adjusted to 1 result
+
+
+
An 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.)
+
+
2.5.1 - Arithmetic Operators
+Lua supports the usual arithmetic operators:
+the binary + (addition),
+- (subtraction), * (multiplication),
+/ (division), % (modulo), and ^ (exponentiation);
+and unary - (negation).
+If the operands are numbers, or strings that can be converted to
+numbers (see 2.2.1),
+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.
+Modulus 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.
+
+
2.5.2 - Relational Operators
+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.
+Objects (tables, userdata, threads, and functions)
+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, thread, or function),
+this new object is different from any previously existing object.
+
+
You can change the way that Lua compares tables and userdata
+by using the "eq" metamethod (see 2.8).
+
+
The conversion rules of 2.2.1
+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 2.8).
+
+
2.5.3 - Logical Operators
+The logical operators in Lua are
+
+
+ and or not
+
+Like the control structures (see 2.4.4),
+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.)
+
+
2.5.4 - Concatenation
+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 2.2.1.
+Otherwise, the "concat" metamethod is called (see 2.8).
+
+
2.5.5 - The Length Operator
+
+
The length operator is denoted by the unary operator #.
+The length of a string is its number of bytes
+(that is, the usual meaning of string length when each
+character is one byte).
+
+
The length of a table t is defined to be any
+integer index n
+such that t[n] is not nil and t[n+1] is nil;
+moreover, if t[1] is nil, n may be zero.
+For a regular array, with non-nil values from 1 to a given n,
+its length is exactly that n,
+the index of its last value.
+If the array has "holes"
+(that is, nil values between other non-nil values),
+then #t may be any of the indices that
+directly precedes a nil value
+(that is, it may consider any such nil value as the end of
+the array).
+
+
2.5.6 - Precedence
+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.
+
+
2.5.7 - Table Constructors
+Table constructors are expressions that create tables.
+Every time a constructor is evaluated, a new table is created.
+Constructors can be used to create empty tables,
+or to create a table and initialize some of its fields.
+The general syntax for constructors is
+
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 2.5.8).
+To avoid this,
+enclose the function call (or the vararg expression)
+in parentheses (see 2.5).
+
+
The field list may have an optional trailing separator,
+as a convenience for machine-generated code.
+
+
2.5.8 - Function Calls
+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 2.8).
+
+
The form
+
+ functioncall ::= prefixexp `:´ Name args
+
+can be used to call "methods".
+A call v:name(...)
+is syntactic sugar for v.name(v,...),
+except that v is evaluated only once.
+
+
+All argument expressions are evaluated before the call.
+A call of the form f{...} is syntactic sugar for f({...});
+that is, the argument list is a single new table.
+A call of the form f'...'
+(or f"..." or f[[...]]) is syntactic sugar for f('...');
+that is, the argument list is a single literal string.
+
+
As an exception to the free-format syntax of Lua,
+you cannot put a line break before the `(´ in a function call.
+This restriction avoids some ambiguities in the language.
+If you write
+
+ a = f
+ (g).x(a)
+
+Lua would see that as a single statement, a = f(g).x(a).
+So, if you want two statements, you must add a semi-colon between them.
+If you actually want to call f,
+you must remove the line break before (g).
+
+
A call of the form returnfunctioncall 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
+
+
+
2.5.9 - Function Definitions
+
+
The syntax for function definition is
+
+ function ::= function funcbody
+ funcbody ::= `(´ [parlist1] `)´ block end
+
+
+
The following syntactic sugar simplifies function definitions:
+
+ stat ::= function funcname funcbody
+ stat ::= localfunction Name funcbody
+ funcname ::= Name {`.´ Name} [`:´ Name]
+
+The statement
+
+ function f () ... end
+
+translates to
+
+ f = function () ... end
+
+The statement
+
+ function t.a.b.c.f () ... end
+
+translates to
+
+ t.a.b.c.f = function () ... end
+
+The statement
+
+ local function f () ... end
+
+translates to
+
+ local f; f = function () ... end
+
+not this:
+
+ local f = function () ... 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 pre-compiles a chunk,
+all its function bodies are pre-compiled 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.
+Different instances of the same function
+may refer to different external local variables
+and may have different environment tables.
+
+
Parameters act as local variables that are
+initialized with the argument values:
+
+ parlist1 ::= 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 variadic or 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 the call 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:
+
Results are returned using the return statement (see 2.4.4).
+If control reaches the end of a function
+without encountering a return statement,
+then the function returns with no results.
+
+
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 (...) ... end
+
+is syntactic sugar for
+
+ t.a.b.c.f = function (self, ...) ... end
+
+
+
2.6 - Visibility Rules
+
+
+
Lua is a lexically scoped language.
+The scope of variables begins at the first statement after
+their declaration and lasts until the end 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.
+
+
2.7 - Error Handling
+
+
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 Lua compilation or execution,
+control returns to C,
+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 the pcall function.
+
+
2.8 - Metatables
+
+
Every value in Lua may 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" in its metatable.
+If it finds one,
+Lua calls this function to perform the addition.
+
+
We call the keys in a metatable events
+and the values 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
+through the getmetatable function.
+
+
You can replace the metatable of tables
+through the setmetatable
+function.
+You cannot change the metatable of other types from Lua
+(except using the debug library);
+you must use the C API for that.
+
+
Tables and userdata have individual metatables
+(although multiple tables and userdata can share
+a same table as their metatable);
+values of all other types share one single metatable per type.
+So, there is one single metatable for all numbers,
+and for all strings, etc.
+
+
A metatable may control how an object behaves in arithmetic operations,
+order comparisons, concatenation, length operation, and indexing.
+A metatable can also define a function to be called when a userdata
+is garbage collected.
+For each of these operations Lua associates a specific key
+called an event.
+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 5.1.
+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)
+
+That is, the access to a metamethod does not invoke other metamethods,
+and the access to objects with no metatables does not fail
+(it simply results in nil).
+
+
+
"add":
+the + 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
+
+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
+
+
+
"sub":
+the - operation.
+Behavior similar to the "add" operation.
+
+
"mul":
+the * operation.
+Behavior similar to the "add" operation.
+
+
"div":
+the / operation.
+Behavior similar to the "add" operation.
+
+
"mod":
+the % operation.
+Behavior similar to the "add" operation,
+with the operation
+o1 - floor(o1/o2)*o2 as the primitive operation.
+
+
"pow":
+the ^ (exponentiation) operation.
+Behavior similar to the "add" operation,
+with the function pow (from the C math library)
+as the primitive operation.
+
+
"unm":
+the unary - 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
+
+
+
"concat":
+the .. (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
+
+
+
"len":
+the # operation.
+
+ function len_event (op)
+ if type(op) == "string" then
+ return strlen(op) -- primitive string length
+ elseif type(op) == "table" then
+ return #op -- primitive table length
+ else
+ local h = metatable(op).__len
+ if h then
+ -- call the handler with the operand
+ return h(op)
+ else -- no handler available: default behavior
+ error("...")
+ end
+ end
+ end
+
+See 2.5.5 for a description of the length of a table.
+
+
"eq":
+the == operation.
+The function getcomphandler defines how Lua chooses a metamethod
+for comparison operators.
+A metamethod only is selected when both objects
+being compared have the same type
+and the same metamethod for the selected operation.
+
+ function getcomphandler (op1, op2, event)
+ if type(op1) ~= type(op2) then return nil end
+ local mm1 = metatable(op1)[event]
+ local mm2 = metatable(op2)[event]
+ if mm1 == mm2 then return mm1 else return nil end
+ end
+
+The "eq" event is defined as follows:
+
+ function eq_event (op1, op2)
+ if type(op1) ~= type(op2) then -- different types?
+ return false -- different objects
+ end
+ if op1 == op2 then -- primitive equal?
+ return true -- objects are equal
+ end
+ -- try metamethod
+ local h = getcomphandler(op1, op2, "__eq")
+ if h then
+ return h(op1, op2)
+ else
+ return false
+ end
+ end
+
+a ~= b is equivalent to not (a == b).
+
+
"lt":
+the < 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 = getcomphandler(op1, op2, "__lt")
+ if h then
+ return h(op1, op2)
+ else
+ error("...");
+ end
+ end
+ end
+
+a > b is equivalent to b < a.
+
+
"le":
+the <= 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 = getcomphandler(op1, op2, "__le")
+ if h then
+ return h(op1, op2)
+ else
+ h = getcomphandler(op1, op2, "__lt")
+ if h then
+ return not h(op2, op1)
+ else
+ error("...");
+ end
+ end
+ end
+ end
+
+a >= b is equivalent to b <= a.
+Note that, in the absence of a "le" metamethod,
+Lua tries the "lt", assuming that a <= b is
+equivalent to not (b < a).
+
+
"index":
+The indexing access table[key].
+
+ function gettable_event (table, key)
+ local h
+ if type(table) == "table" then
+ local v = rawget(table, key)
+ 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
+
+ function settable_event (table, key, value)
+ local h
+ if type(table) == "table" then
+ local v = rawget(table, key)
+ 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
+ return h(table, key,value) -- call the handler
+ else h[key] = value -- or repeat operation on it
+ end
+ end
+
+
+
"call":
+called when Lua calls a value.
+
+ 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
+
+
+
+
+
2.9 - Environments
+
+
Besides metatables,
+objects of types thread, function, and userdata
+have another table associated with them,
+called their environment.
+Like metatables, environments are regular tables and
+multiple objects can share the same environment.
+
+
Environments associated with userdata have no meaning for Lua.
+It is only a feature for programmers to associate a table to
+a userdata.
+
+
Environments associated with threads are called
+global environments.
+They are used as the default environment for threads and
+non-nested functions created by the thread
+(through loadfile, loadstring or load)
+and can be directly accessed by C code (see 3.3).
+
+
Environments associated with C functions can be directly
+accessed by C code (see 3.3).
+They are used as the default environment for other C functions
+created by the function.
+
+
Environments associated with Lua functions are used to resolve
+all accesses to global variables within the function (see 2.3).
+They are used as the default environment for other Lua functions
+created by the function.
+
+
You can change the environment of a Lua function or the
+running thread by calling setfenv.
+You can get the environment of a Lua function or the running thread
+by calling getfenv.
+To manipulate the environment of other objects
+(userdata, C functions, other threads) you must
+use the C API.
+
+
2.10 - Garbage Collection
+
+
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 from time to time
+to collect all dead objects
+(that is, these objects that are no longer accessible from Lua).
+All objects in Lua are subject to automatic management:
+tables, userdata, functions, threads, and strings.
+
+
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.
+
+
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 1 mean the collector will not wait to
+start a new cycle.
+A value of 2 means that the collector waits for the total memory in use
+to double before starting a new cycle.
+
+
The step multiplier
+controls the relative speed of the collector relative to
+memory allocation.
+Larger values make the collector more aggressive but also increases
+the size of each incremental step.
+Values smaller than 1 make the collector too slow and
+may result in the collector never finishing a cycle.
+The default, 2, means that the collector runs at "twice"
+the speed of memory allocation.
+
+
You can change these numbers by calling lua_gc in C
+or collectgarbage in Lua.
+Both get as arguments percentage points
+(so an argument 100 means a real value of 1).
+With these functions you can also control
+the collector directly (e.g., stop and restart it).
+
+
2.10.1 - Garbage-Collection Metamethods
+
+
Using the C API,
+you can set garbage-collector metamethods for userdata (see 2.8).
+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).
+
+
Garbage userdata with a field __gc in their metatables are not
+collected immediately by the garbage collector.
+Instead, Lua puts them in a list.
+After the collection,
+Lua does the equivalent of the following function
+for each userdata in that list:
+
+ function gc_event (udata)
+ local h = metatable(udata).__gc
+ if h then
+ h(udata)
+ end
+ end
+
+
+
At the end of each garbage-collection cycle,
+the finalizers for userdata are called in reverse
+order of their creation,
+among those collected in that cycle.
+That is, the first finalizer to be called is the one associated
+with the userdata created last in the program.
+
+
2.10.2 - Weak Tables
+
+
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 this 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 value of 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.
+
+
After you use a table as a metatable,
+you should not change the value of its field __mode.
+Otherwise, the weak behavior of the tables controlled by this
+metatable is undefined.
+
+
2.11 - Coroutines
+
+
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 with a call to 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 execution.
+
+
When you first call coroutine.resume,
+passing as its first argument
+the 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.
+
+
The coroutine.wrap function creates a coroutine,
+just like coroutine.create,
+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,
+consider the next 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
+
+
+
+
3 - The Application Program Interface
+
+
+
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.
+All such macros use each of its 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 a proper definition for the macro luai_apicheck,
+in file luaconf.h.
+
+
3.1 - The Stack
+
+
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.
+We say that an index is valid
+if it lies between 1 and the stack top
+(that is, if 1 <= abs(index) <= top).
+
+
+
3.2 - Stack Size
+
+
When you interact with 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 grow the stack size.
+
+
Whenever Lua calls C,
+it ensures that at least LUA_MINSTACK stack positions are available.
+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.
+
+
Most query functions accept as indices any value inside the
+available stack space, that is, indices up to the maximum stack size
+you have set through lua_checkstack.
+Such indices are called acceptable indices.
+More formally, we define an acceptable index
+as follows:
+
Unless otherwise noted,
+any function that accepts valid indices can also be called with
+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 thread environment,
+the function environment,
+the registry,
+and the upvalues of a C function (see 3.4).
+
+
The thread environment (where global variables live) is
+always at pseudo-index LUA_GLOBALSINDEX.
+The environment of the running C function is always
+at pseudo-index LUA_ENVIRONINDEX.
+
+
To access and change the value of global variables,
+you can use regular table operations over an environment table.
+For instance, to access the value of a global variable, do
+
+ lua_getfield(L, LUA_GLOBALSINDEX, varname);
+
+
+
3.4 - C Closures
+
+
When a C function is created,
+it is possible to associate some values with it,
+thus creating a C closure;
+these values are called upvalues and are
+accessible to the function whenever it is called
+(see lua_pushcclosure).
+
+
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,
+produces an acceptable (but invalid) index.
+
+
3.5 - Registry
+
+
Lua provides a registry,
+a pre-defined table that can be used by any C code to
+store whatever Lua value it needs to store.
+This table is always located at pseudo-index
+LUA_REGISTRYINDEX.
+Any C library can store data into this table,
+but it should take care to choose keys 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.
+
+
The integer keys in the registry are used by the reference mechanism,
+implemented by the auxiliary library,
+and therefore should not be used for other purposes.
+
+
3.6 - Error Handling in C
+
+
Internally, Lua uses the C longjmp facility to handle errors.
+(You can also choose to use exceptions if you use C++;
+See file luaconf.h.)
+When Lua faces any error
+(such as memory allocation errors, 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 recover point;
+any error jumps to the most recent active recover point.
+
+
Almost any function in the API may raise an error,
+for instance due to a memory allocation error.
+The following functions run in protected mode
+(that is, they create a protected environment to run),
+so they never raise an error:
+lua_newstate, lua_close, lua_load,
+lua_pcall, and lua_cpcall.
+
+
Inside a C function you can raise an error by calling lua_error.
+
+
3.7 - Functions and Types
+
+
Here we list all functions and types from the C API in
+alphabetical order.
+
+
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;
+nsize, the new size of the block.
+ptr is NULL if and only if osize is zero.
+When nsize is zero, the allocator must return NULL;
+if osize is not zero,
+it should free the block pointed to by ptr.
+When nsize is not zero, the allocator returns NULL
+if and only if it cannot fill the request.
+When nsize is not zero and osize is zero,
+the allocator should behave like malloc.
+When nsize and osize are not zero,
+the allocator behaves like realloc.
+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 lua_newstate.
+
+static void *l_alloc (void *ud, void *ptr, size_t osize, size_t nsize) {
+ (void)ud; /* not used */
+ (void)osize; /* not used */
+ if (nsize == 0) {
+ free(ptr); /* ANSI requires that free(NULL) has no effect */
+ return NULL;
+ }
+ else
+ /* ANSI requires that realloc(NULL, size) == malloc(size) */
+ return realloc(ptr, nsize);
+}
+
Sets a new panic function and returns the old one.
+
+
If an error happens outside any protected environment,
+Lua calls a panic function
+and then calls exit(EXIT_FAILURE),
+thus exiting the host application.
+Your panic function may avoid this exit by
+never returning (e.g., doing a long jump).
+
+
The panic function can access the error message at the top of the stack.
+
+
+
lua_call
+
+ 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 may do the
+equivalent to this Lua code:
+
+ a = f("how", t.x, 14)
+
+Here it is in C:
+
+ lua_getfield(L, LUA_GLOBALSINDEX, "f"); /* function to be called */
+ lua_pushstring(L, "how"); /* 1st argument */
+ lua_getfield(L, LUA_GLOBALSINDEX, "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 function with 3 arguments and 1 result */
+ lua_setfield(L, LUA_GLOBALSINDEX, "a"); /* set global variable `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_CFunction
+
+ typedef 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 to function `average'");
+ 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
+
+ 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 grow the stack to that size.
+This function never shrinks the stack;
+if the stack is already larger than the new size,
+it is left unchanged.
+
+
+
lua_close
+
+ 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,
+such as a daemon or a web server,
+might need to release states as soon as they are not needed,
+to avoid growing too large.
+
+
+
lua_concat
+
+ 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 string on the stack
+(that is, the function does nothing);
+if n is 0, the result is the empty string.
+Concatenation is done following the usual semantics of Lua
+(see 2.5.4).
+
+
+
lua_cpcall
+
+ int lua_cpcall (lua_State *L, lua_CFunction func, void *ud);
+
+
+
+
Calls the C function func in protected mode.
+func starts with only one element in its stack,
+a light userdata containing ud.
+In case of errors,
+lua_cpcall returns the same error codes as lua_pcall,
+plus the error object on the top of the stack;
+otherwise, it returns zero, and does not change the stack.
+All values returned by func are discarded.
+
+
+
lua_createtable
+
+ void lua_createtable (lua_State *L, int narr, int nrec);
+
+
+
+
Creates a new empty table and pushes it onto the stack.
+The new table has space pre-allocated
+for narr array elements and nrec non-array elements.
+This pre-allocation is useful when you know exactly how many elements
+the table will have.
+Otherwise you can use the function lua_newtable.
+
+
+
lua_dump
+
+ 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_equal
+
+ int lua_equal (lua_State *L, int index1, int index2);
+
+
+
+
Returns 1 if the two values in acceptable indices index1 and
+index2 are equal,
+following the semantics of the Lua == operator
+(that is, may call metamethods).
+Otherwise returns 0.
+Also returns 0 if any of the indices is non valid.
+
+
+
lua_error
+
+ 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
+
+ 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 tune experimentally the value of data.
+The function returns 1 if the step finished a
+garbage-collection cycle.
+
LUA_GCSETPAUSE---
+sets data/100 as the new value
+for the pause of the collector (see 2.10).
+The function returns the previous value of the pause.
+
LUA_GCSETSTEPMUL---
+sets arg/100 as the new value for the step multiplier of
+the collector (see 2.10).
+The function returns the previous value of the step multiplier.
+
Pushes onto the stack the value t[k],
+where t is the value at the given valid index index.
+As in Lua, this function may trigger a metamethod
+for the "index" event (see 2.8).
+
+
+ int lua_getmetatable (lua_State *L, int index);
+
+
+
+
Pushes onto the stack the metatable of the value at the given
+acceptable index.
+If the index is not valid,
+or if the value does not have a metatable,
+the function returns 0 and pushes nothing on the stack.
+
+
+
lua_gettable
+
+ void lua_gettable (lua_State *L, int index);
+
+
+
+
Pushes onto the stack the value t[k],
+where t is the value at the given valid index 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 2.8).
+
+
+
lua_gettop
+
+ 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_insert
+
+ 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.
+Cannot be called with a pseudo-index,
+because a pseudo-index is not an actual stack position.
+
+
+
lua_Integer
+
+ typedef ptrdiff_t lua_Integer;
+
+
+
+
The type used by the Lua API to represent integral values.
+
+
By default it is a ptrdiff_t,
+which is usually the largest integral type the machine handles
+"comfortably".
+
+
+
lua_isboolean
+
+ int lua_isboolean (lua_State *L, int index);
+
+
+
+
Returns 1 if the value at the given acceptable index has type boolean,
+and 0 otherwise.
+
+
+
lua_iscfunction
+
+ int lua_iscfunction (lua_State *L, int index);
+
+
+
+
Returns 1 if the value at the given acceptable index is a C function,
+and 0 otherwise.
+
+
+
lua_isfunction
+
+ int lua_isfunction (lua_State *L, int index);
+
+
+
+
Returns 1 if the value at the given acceptable index is a function
+(either C or Lua), and 0 otherwise.
+
+
+
lua_islightuserdata
+
+ int lua_islightuserdata (lua_State *L, int index);
+
+
+
+
Returns 1 if the value at the given acceptable index is a light userdata,
+and 0 otherwise.
+
+
+
lua_isnil
+
+ int lua_isnil (lua_State *L, int index);
+
+
+
+
Returns 1 if the value at the given acceptable index is nil,
+and 0 otherwise.
+
+
+
lua_isnumber
+
+ int lua_isnumber (lua_State *L, int index);
+
+
+
+
Returns 1 if the value at the given acceptable index is a number
+or a string convertible to a number,
+and 0 otherwise.
+
+
+
lua_isstring
+
+ int lua_isstring (lua_State *L, int index);
+
+
+
+
Returns 1 if the value at the given acceptable index is a string
+or a number (which is always convertible to a string),
+and 0 otherwise.
+
+
+
lua_istable
+
+ int lua_istable (lua_State *L, int index);
+
+
+
+
Returns 1 if the value at the given acceptable index is a table,
+and 0 otherwise.
+
+
+
lua_isthread
+
+ int lua_isthread (lua_State *L, int index);
+
+
+
+
Returns 1 if the value at the given acceptable index is a thread,
+and 0 otherwise.
+
+
+
lua_isuserdata
+
+ int lua_isuserdata (lua_State *L, int index);
+
+
+
+
Returns 1 if the value at the given acceptable index is a userdata
+(either full or light), and 0 otherwise.
+
+
+
lua_lessthan
+
+ int lua_lessthan (lua_State *L, int index1, int index2);
+
+
+
+
Returns 1 if the value at acceptable index index1 is smaller
+than the value at acceptable index index2,
+following the semantics of the Lua < operator
+(that is, may call metamethods).
+Otherwise returns 0.
+Also returns 0 if any of the indices is non valid.
+
+
Loads a Lua chunk.
+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:
+
+
0 --- no errors;
+
LUA_ERRSYNTAX ---
+syntax error during pre-compilation.
+
LUA_ERRMEM ---
+memory allocation error.
+
+
+
lua_load automatically detects whether the chunk is text or binary,
+and loads it accordingly (see program luac).
+
+
lua_load uses a user-supplied reader function to read the chunk
+(see lua_Reader).
+The data argument is an opaque value passed to the reader function.
+
+
The chunkname argument gives a name to the chunk,
+which is used for error messages and in debug information (see 3.8).
+
+
Creates a new, independent state.
+Returns NULL if cannot create 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
+simply passes to the allocator in every call.
+
+
+
lua_newtable
+
+ void lua_newtable (lua_State *L);
+
+
+
+
Creates a new empty table and pushes it onto the stack.
+Equivalent to lua_createtable(L, 0, 0).
+
+
+
lua_newthread
+
+ 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 state returned by this function shares with the original state
+all global objects (such as tables),
+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.
+
+
This function allocates a new block of memory with the given size,
+pushes on the stack a new full userdata with the block address,
+and returns this address.
+
+
Userdata represents C values in Lua.
+A full userdata represents a block of memory.
+It is an object (like a table):
+You must create it, it can have its own metatable,
+and you can detect when it is being collected.
+A full userdata is only equal to itself (under raw equality).
+
+
When Lua collects a full userdata with a gc metamethod,
+Lua calls the metamethod and marks the userdata as finalized.
+When this userdata is collected again then
+Lua frees its corresponding memory.
+
+
+
lua_next
+
+ 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) {
+ /* `key' is 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)));
+ lua_pop(L, 1); /* removes `value'; keeps `key' for next iteration */
+ }
+
+
+
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_tolstringchanges
+the value at the given index;
+this confuses the next call to lua_next.
+
+
+
lua_Number
+
+ typedef double lua_Number;
+
+
+
+
The type of numbers in Lua.
+By default, it is double, but that can be changed in luaconf.h.
+
+
Through the configuration file you can change
+Lua to operate with another type for numbers (e.g., float or long).
+
+
+
lua_objlen
+
+ size_t lua_objlen (lua_State *L, int index);
+
+
+
+
Returns the "length" of the value at the given acceptable index:
+for strings, this is the string length;
+for tables, this is the result of the length operator (`#´);
+for userdata, this is the size of the block of memory allocated
+for the userdata;
+for other values, it is 0.
+
+
+
lua_pcall
+
+ lua_pcall (lua_State *L, int nargs, int nresults, int errfunc);
+
+
+
+
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 errfunc is 0,
+then the error message returned on the stack
+is exactly the original error message.
+Otherwise, errfunc is the stack index of an
+error handler function.
+(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 error handler function 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 0 in case of success
+or one of the following error codes
+(defined in lua.h):
+
+
LUA_ERRRUN --- a runtime error.
+
LUA_ERRMEM --- memory allocation error.
+For such errors, Lua does not call the error handler function.
+
LUA_ERRERR ---
+error while running the error handler function.
+
+
+
+
lua_pop
+
+ void lua_pop (lua_State *L, int n);
+
+
+
+
Pops n elements from the stack.
+
+
+
lua_pushboolean
+
+ void lua_pushboolean (lua_State *L, int b);
+
+
+
+
Pushes a boolean value with value b onto the stack.
+
+
+
lua_pushcclosure
+
+ 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 3.4);
+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.
+
+
Pushes a C function onto the stack.
+This function receives a pointer to a C function
+and pushes on 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).
+
+
The call lua_pushcfunction(L, f) is equivalent to
+lua_pushcclosure(L, f, 0).
+
+
Pushes onto the stack a formatted string
+and returns a pointer to this string.
+It is similar to the C function sprintf,
+but has some important differences:
+
+
You do not have to allocate space for the result:
+The result is a Lua string and Lua takes care of memory allocation
+(and deallocation, through garbage collection).
+
The conversion specifiers are quite restricted.
+There are no flags, widths, or precisions.
+The conversion specifiers can only be
+`%%´ (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 character).
+
Userdata represents C values in Lua.
+A light userdata represents a pointer.
+It is a value (like a number):
+You do not create it, it has no metatables,
+it is not collected (as it was never created).
+A light userdata is equal to "any"
+light userdata with the same C address.
+
+
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 embedded zeros.
+
+
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.
+The string cannot contain embedded zeros;
+it is assumed to end at the first zero.
+
+
+
lua_pushthread
+
+ void lua_pushthread (lua_State *L);
+
+
+
+
Pushes the thread represented by L onto the stack.
+
+
+
lua_pushvalue
+
+ void lua_pushvalue (lua_State *L, int index);
+
+
+
+
Pushes a copy of the element at the given valid index
+onto the stack.
+
+
Equivalent to lua_pushfstring, except that it receives a va_list
+instead of a variable number of arguments.
+
+
+
lua_rawequal
+
+ int lua_rawequal (lua_State *L, int index1, int index2);
+
+
+
+
Returns 1 if the two values in acceptable 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
+
+ void lua_rawget (lua_State *L, int index);
+
+
+
+
Similar to lua_gettable, but does a raw access
+(i.e., without metamethods).
+
+
+
lua_rawgeti
+
+ void lua_rawgeti (lua_State *L, int index, int n);
+
+
+
+
Pushes onto the stack the value t[n],
+where t is the value at the given valid index index.
+The access is raw;
+that is, it does not invoke metamethods.
+
+
+
lua_rawset
+
+ void lua_rawset (lua_State *L, int index);
+
+
+
+
Similar to lua_settable, but does a raw assignment
+(i.e., without metamethods).
+
+
+
lua_rawseti
+
+ void lua_rawseti (lua_State *L, int index, int n);
+
+
+
+
Does the equivalent of t[n] = v,
+where t is the value at the given valid index 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.
+
+
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.
+The reader function may return pieces of any size greater than zero.
+
+
Removes the element at the given valid index,
+shifting down the elements above this index to fill the gap.
+Cannot be called with a pseudo-index,
+because a pseudo-index is not an actual stack position.
+
+
+
lua_replace
+
+ void lua_replace (lua_State *L, int index);
+
+
+
+
Moves the top element into the given position (and pops it),
+without shifting any element
+(therefore replacing the value at the given position).
+
+
+
lua_resume
+
+ int lua_resume (lua_State *L, int narg);
+
+
+
+
Starts and resumes a coroutine in a given thread.
+
+
To start a coroutine, you first create a new thread
+(see lua_newthread);
+then you push on its stack the main function plus any eventual arguments;
+then you call lua_resume,
+with narg 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,
+0 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 restart a coroutine, you put on its stack only the values to
+be passed as results from yield,
+and then call lua_resume.
+
+
Changes the allocator function of a given state to f
+with user data ud.
+
+
+
lua_setfenv
+
+ int lua_setfenv (lua_State *L, int index);
+
+
+
+
Pops a table from the stack and sets it as
+the new environment for the value at the given index.
+If the value at the given index is
+neither a function nor a thread nor a userdata,
+lua_setfenv returns 0.
+Otherwise it returns 1.
+
+
+ int 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
+acceptable index.
+
+
+
lua_settable
+
+ void lua_settable (lua_State *L, int index);
+
+
+
+
Does the equivalent to t[k] = v,
+where t is the value at the given valid index 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 2.8).
+
+
+
lua_settop
+
+ void lua_settop (lua_State *L, int index);
+
+
+
+
Accepts any acceptable 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_State
+
+ typedef struct lua_State lua_State;
+
+
+
+
Opaque structure that keeps the whole state of a Lua interpreter.
+The Lua library is fully reentrant:
+it has no global variables.
+All information about a state is kept in this structure.
+
+
A pointer to this state 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
+
+ int lua_status (lua_State *L);
+
+
+
+
Returns the status of the thread L.
+
+
The status can be 0 for a normal thread,
+an error code if the thread finished its execution with an error,
+or LUA_YIELD if the thread is suspended.
+
+
+
lua_toboolean
+
+ int lua_toboolean (lua_State *L, int index);
+
+
+
+
Converts the Lua value at the given acceptable index to a C boolean
+value (0 or 1).
+Like all tests in Lua,
+lua_toboolean returns 1 for any Lua value
+different from false and nil;
+otherwise it returns 0.
+It also returns 0 when called with a non-valid index.
+(If you want to accept only actual boolean values,
+use lua_isboolean to test the value's type.)
+
+
+
lua_tocfunction
+
+ lua_CFunction lua_tocfunction (lua_State *L, int index);
+
+
+
+
Converts a value at the given acceptable index to a C function.
+That value must be a C function;
+otherwise, returns NULL.
+
+
+
lua_tointeger
+
+ lua_Integer lua_tointeger (lua_State *L, int idx);
+
+
+
+
Converts the Lua value at the given acceptable index
+to the signed integral type lua_Integer.
+The Lua value must be a number or a string convertible to a number
+(see 2.2.1);
+otherwise, lua_tointeger returns 0.
+
+
If the number is not an integer,
+it is truncated in some non-specified way.
+
+
Converts the Lua value at the given acceptable index to a string
+(const char*).
+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 may 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
+
+ lua_Number lua_tonumber (lua_State *L, int index);
+
+
+
+
Converts the Lua value at the given acceptable index
+to a number (see lua_Number).
+The Lua value must be a number or a string convertible to a number
+(see 2.2.1);
+otherwise, lua_tonumber returns 0.
+
+
+
lua_topointer
+
+ const void *lua_topointer (lua_State *L, int index);
+
+
+
+
Converts the value at the given acceptable index to a generic
+C pointer (void*).
+The value may be a userdata, a table, a thread, or a function;
+otherwise, lua_topointer returns NULL.
+Lua ensures that different objects return different pointers.
+There is no direct way to convert the pointer back to its original value.
+
+
Typically this function is used only for debug information.
+
+
+
lua_tostring
+
+ const char *lua_tostring (lua_State *L, int index);
+
+
+
+
Equivalent to lua_tolstring with len equal to NULL.
+
+
+
lua_tothread
+
+ lua_State *lua_tothread (lua_State *L, int index);
+
+
+
+
Converts the value at the given acceptable index to a Lua thread
+(represented as lua_State*).
+This value must be a thread;
+otherwise, the function returns NULL.
+
+
+
lua_touserdata
+
+ void *lua_touserdata (lua_State *L, int index);
+
+
+
+
If the value at the given acceptable index is a full userdata,
+returns its block address.
+If the value is a light userdata,
+returns its pointer.
+Otherwise, returns NULL.
+
+
+
lua_type
+
+ int lua_type (lua_State *L, int index);
+
+
+
+
Returns the type of the value in the given acceptable index,
+or LUA_TNONE for a non-valid index
+(that is, an index to an "empty" stack position).
+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
+
+ 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.
+
+
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 global 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);
+
+
+
+
Yields a coroutine.
+
+
This function should only be called as the
+return expression of a C function, as follows:
+
+ return lua_yield (L, nresults);
+
+When a C function calls lua_yield 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.
+
+
+
3.8 - The Debug Interface
+
+
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_Debug
+
+ typedef 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 nups; /* (u) number of upvalues */
+ int linedefined; /* (S) */
+ int lastlinedefined; /* (S) */
+ char short_src[LUA_IDSIZE]; /* (S) */
+ /* private part */
+ ...
+ } lua_Debug;
+
+
+
+
+
A structure used to carry different pieces of
+information about an active function.
+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 ---
+If the function was defined in a string,
+then source is that string.
+If the function was defined in a file,
+then source starts with a `@´ followed by the file name.
+
+
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,
+and "tail" if it was a function that did a tail call.
+In the latter case,
+Lua has no other information about the function.
+
+
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 may be the value of multiple global variables,
+while others may 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.)
+
+
nups ---
+the number of upvalues of the function.
+
+
Fills the fields of lua_Debug with useful information.
+
+
This function returns 0 on error
+(for instance, an invalid option in what).
+Each character in the string what
+selects some fields of the structure ar to be filled,
+as indicated by the letter in parentheses in the definition of lua_Debug:
+`S´ fills in the fields source, linedefined,
+lastlinedefined,
+and what;
+`l´ fills in the field currentline, etc.
+Moreover, `f´ pushes onto the stack the function that is
+running at the given level.
+
+
To get information about a function that is not active
+(that is, not in the stack),
+you push it onto the stack
+and start the what string with the character `>´.
+For instance, to know in which line a function f was defined,
+you can write the following code:
+
+ lua_Debug ar;
+ lua_getfield(L, LUA_GLOBALSINDEX, "f"); /* get global `f' */
+ lua_getinfo(L, ">S", &ar);
+ printf("%d\n", ar.linedefined);
+
Gets information about a local variable of a given activation record.
+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
+(1 is the first parameter or active local variable, and so on,
+until the last active local variable).
+lua_getlocal pushes the variable's value onto the stack
+and returns its name.
+
+
Variable names starting with `(´ (open parentheses)
+represent internal variables
+(loop control variables, temporaries, and C function locals).
+
+
Returns NULL (and pushes nothing)
+when the index is greater than
+the number of active local variables.
+
+
+
lua_getstack
+
+ int lua_getstack (lua_State *L, int level, lua_Debug *ar);
+
+
+
+
Get 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.
+When there are no errors, lua_getstack returns 1;
+when called with a level greater than the stack depth,
+it returns 0.
+
+
+
lua_getupvalue
+
+ 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.
+
+
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_HOOKTAILRET, 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 return events, event may be LUA_HOOKRET,
+the normal value, or LUA_HOOKTAILRET.
+In the latter case, Lua is simulating a return from
+a function that did a tail call;
+in this case, it is useless to call lua_getinfo.
+
+
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.
+
+
+
lua_sethook
+
+ int lua_sethook (lua_State *L, lua_Hook func, int mask, int count);
+
+
+
+
Sets the debugging hook function.
+
+
func 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:
+
+
The call hook is called when the interpreter calls a function.
+The hook is called just after Lua enters the new function,
+before the function gets its arguments.
+
The return hook is called when the interpreter returns from a function.
+The hook is called just before Lua leaves the function.
+You have no access to the values to be returned by the function.
+
The line hook is called when the interpreter is about to
+start the execution of a new line of code,
+or when it jumps back in the code (even to the same line).
+(This event only happens while Lua is executing a Lua function.)
+
The count hook is called after the interpreter executes every
+count instructions.
+(This event only happens while Lua is executing a Lua function.)
+
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
+
+ const char *lua_setupvalue (lua_State *L, int funcindex, int n);
+
+
+
+
Sets the value of a closure's upvalue.
+Parameters funcindex and n are as in lua_getupvalue
+(see lua_getupvalue).
+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.
+
+
Returns NULL (and pops nothing)
+when the index is greater than the number of upvalues.
+
+
+
4 - The Auxiliary Library
+
+
+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 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 this API.
+
+
Several functions in the auxiliary library are used to
+check C function arguments.
+Their names are always luaL_check* or luaL_opt*.
+All of these functions raise an error if the check is not satisfied.
+Because the error message is formatted for arguments
+(e.g., "bad argument #1"),
+you should not use these functions for other stack values.
+
+
4.1 - Functions and Types
+
+
Here we list all functions and types from the auxiliary library
+in alphabetical order.
+
+
+
luaL_addchar
+
+ void luaL_addchar (luaL_Buffer B, char c);
+
+
+
+
Adds the character c to the buffer B
+(see luaL_Buffer).
+
+
Adds the zero-terminated string pointed to by s
+to the buffer B
+(see luaL_Buffer).
+The string may not contain embedded zeros.
+
+
+
luaL_addvalue
+
+ 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
+
+ void luaL_argcheck (lua_State *L, int cond, int numarg,
+ const char *extramsg);
+
+
+
+
Checks whether cond is true.
+If not, raises an error with message
+"bad argument #<numarg> to <func> (<extramsg>)",
+where func is retrieved from the call stack.
+
+
+
luaL_argerror
+
+ int luaL_argerror (lua_State *L, int numarg, const char *extramsg);
+
+
+
+
Raises an error with message
+"bad argument #<numarg> to <func> (<extramsg>)",
+where func is retrieved from the call stack.
+
+
This function never returns,
+but it is an idiom to use it as return luaL_argerror ...
+in C functions.
+
+
+
luaL_Buffer
+
+ typedef 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:
+
+
First you declare a variable b of type luaL_Buffer.
+
Then you initialize it with a call luaL_buffinit(L, &b).
+
Then you add string pieces to the buffer calling any of
+the luaL_add* functions.
+
You finish by calling luaL_pushresult(&b).
+This call leaves the final string on the top of the stack.
+
+
+
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.
+
+
Initializes a buffer B.
+This function does not allocate any space;
+the buffer must be declared as a variable
+(see luaL_Buffer).
+
+
+
luaL_callmeta
+
+ 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 and passes the object as its only argument.
+In this case this function returns 1 and pushes on the
+stack the value returned by the call.
+If there is no metatable or no metamethod,
+this function returns 0 (without pushing any value on the stack).
+
+
+
luaL_checkany
+
+ void luaL_checkany (lua_State *L, int narg);
+
+
+
+
Checks whether the function has an argument
+of any type (including nil) at position narg.
+
+
+
luaL_checkint
+
+ int luaL_checkint (lua_State *L, int narg);
+
+
+
+
Checks whether the function argument narg is a number
+and returns this number cast to an int.
+
+
+
luaL_checkinteger
+
+ lua_Integer luaL_checkinteger (lua_State *L, int narg);
+
+
+
+
Checks whether the function argument narg is a number
+and returns this number cast to a lua_Integer.
+
+
+
luaL_checklong
+
+ long luaL_checklong (lua_State *L, int narg);
+
+
+
+
Checks whether the function argument narg is a number
+and returns this number cast to a long.
+
+
Checks whether the function argument narg is a string
+and returns this string;
+if l is not NULL fills *l
+with the string's length.
+
+
+
luaL_checknumber
+
+ lua_Number luaL_checknumber (lua_State *L, int narg);
+
+
+
+
Checks whether the function argument narg is a number
+and returns this number.
+
+
+
luaL_checkoption
+
+ int luaL_checkoption (lua_State *L, int narg, const char *def,
+ const char *const lst[]);
+
+
+
+
Checks whether the function argument narg is a string and
+searches for this string in the array lst
+(which must be NULL-terminated).
+If def is not NULL,
+uses def as a default value when
+the function has no argument narg or if this argument is nil.
+
+
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.
+
+
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.
+
+
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.
+
+
+
luaL_checkstring
+
+ const char *luaL_checkstring (lua_State *L, int narg);
+
+
+
+
Checks whether the function argument narg is a string
+and returns this string.
+
+
+
luaL_checktype
+
+ void luaL_checktype (lua_State *L, int narg, int t);
+
+
+
+
Checks whether the function argument narg has type t.
+
+
Checks whether the function argument narg is a userdata
+of the type tname (see luaL_newmetatable).
+
+
+
luaL_error
+
+ 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 as return luaL_error ...
+in C functions.
+
+
+
luaL_getmetafield
+
+ int luaL_getmetafield (lua_State *L, int obj, const char *e);
+
+
+
+
Pushes on 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 0 and pushes nothing.
+
+
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.
+
+
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.
+
+
+
luaL_loadfile
+
+ int luaL_loadfile (lua_State *L, const char *filename);
+
+
+
+
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 #.
+
+
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.
+
+
+
luaL_loadstring
+
+ 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.
+
+
+
luaL_newmetatable
+
+ 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 on the stack the final value associated
+with tname in the registry.
+
+
+
luaL_newstate
+
+ lua_State *luaL_newstate (void);
+
+
+
+
Creates a new Lua state, calling lua_newstate with an
+allocation function based on the standard C realloc function
+and setting a panic function (see lua_atpanic) 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
+
+ void luaL_openlibs (lua_State *L);
+
+
+
+
Opens all standard Lua libraries into the given state.
+
+
+
luaL_optint
+
+ int luaL_optint (lua_State *L, int narg, int d);
+
+
+
+
If the function argument narg 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
+
+ lua_Integer luaL_optinteger (lua_State *L, int narg, lua_Integer d);
+
+
+
+
If the function argument narg 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
+
+ long luaL_optlong (lua_State *L, int narg, long d);
+
+
+
+
If the function argument narg is a number,
+returns this number cast to a long.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
If the function argument narg is a string,
+returns this string.
+If this argument is absent or is nil,
+returns d.
+Otherwise, raises an error.
+
+
+
luaL_prepbuffer
+
+ char *luaL_prepbuffer (luaL_Buffer *B);
+
+
+
+
Returns an address to a space of size LUAL_BUFFERSIZE
+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
+
+ void luaL_pushresult (luaL_Buffer *B);
+
+
+
+
Finishes the use of buffer B leaving the final string on
+the top of the stack.
+
+
+
luaL_ref
+
+ 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.
+
+
Type for arrays of functions to be registered by
+luaL_register.
+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.
+
+
When called with libname equal to NULL,
+simply registers all functions in the list l
+(see luaL_Reg) into the table on the top of the stack.
+
+
When called with a non-null libname,
+creates a new table t,
+sets it as the value of the global variable libname,
+sets it as the value of package.loaded[libname],
+and registers on it all functions in the list l.
+If there is a table in package.loaded[libname] or in
+variable libname,
+reuses this table instead of creating a new one.
+
+
In any case the function leaves the table
+on the top of the stack.
+
+
+
luaL_typename
+
+ const char *luaL_typename (lua_State *L, int idx);
+
+
+
+
Returns the name of the type of the value at index idx.
+
+
+
luaL_typerror
+
+ int luaL_typerror (lua_State *L, int narg, const char *tname);
+
+
+
+
Generates an error with a message like
+
+<location>: bad argument <narg> to <function> (<tname> expected, got <realt>)
+
+where <location> is produced by luaL_where,
+<function> is the name of the current function,
+and <realt> is the type name of the actual argument.
+
+
+
luaL_unref
+
+ 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
+
+ void luaL_where (lua_State *L, int lvl);
+
+
+
+
Pushes on the stack a string identifying the current position
+of the control at level lvl in the call stack.
+Typically this string has the 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.
+
+
+
5 - Standard Libraries
+
+
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., sort).
+
+
All libraries are implemented through the official C API
+and are provided as separate C modules.
+Currently, Lua has the following standard libraries:
+
+
basic library;
+
package library;
+
string manipulation;
+
table manipulation;
+
mathematical functions (sin, log, etc.);
+
input and output;
+
operating system facilities;
+
debug facilities.
+
+Except for the basic and 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 must call
+luaL_openlibs,
+which open all standard libraries.
+Alternatively,
+it can open them individually by calling
+luaopen_base (for the basic library),
+luaopen_package (for the package library),
+luaopen_string (for the string library),
+luaopen_table (for the table library),
+luaopen_math (for the mathematical library),
+luaopen_io (for the I/O and the Operating System libraries),
+and luaopen_debug (for the debug library).
+These functions are declared in lualib.h
+and should not be called directly:
+you must call them like any other Lua C function,
+e.g., by using lua_call.
+
+
5.1 - Basic Functions
+
+
The basic library provides some 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])
+Issues an error when
+the value of its argument 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:
+
+
"stop" --- stops the garbage collector.
+
"restart" --- restarts the garbage collector.
+
"collect" --- performs a full garbage-collection cycle.
+
"count" --- returns the total memory in use by Lua (in Kbytes).
+
"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 tune experimentally the value of arg.
+Returns true if the step finished a collection cycle.
+
"steppause" ---
+sets arg/100 as the new value for the pause of
+the collector (see 2.10).
+
"setstepmul" ---
+sets arg/100 as the new value for the step multiplier of
+the collector (see 2.10).
+
+
+
dofile (filename)
+Opens the named file and executes its contents as a Lua chunk.
+When called without arguments,
+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])
+Terminates the last protected function called
+and returns message as the error message.
+Function error never returns.
+
+
Usually, error adds some information about the error position
+at the beginning of the message.
+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
+A global variable (not a function) that
+holds the global environment (that is, _G._G = _G).
+Lua itself does not use this variable;
+changing its value does not affect any environment,
+nor vice-versa.
+(Use setfenv to change environments.)
+
+
getfenv (f)
+Returns the current environment in use by the function.
+f can be a Lua function or a number
+that specifies the function at that stack level:
+Level 1 is the function calling getfenv.
+If the given function is not a Lua function,
+or if f is 0,
+getfenv returns the global environment.
+The default for f is 1.
+
+
getmetatable (object)
+
+
If object does not have a metatable, returns nil.
+Otherwise,
+if the object's metatable has a "__metatable" field,
+returns the associated value.
+Otherwise, returns the metatable of the given object.
+
+
ipairs (t)
+
+
Returns three values: an iterator function, the table t, and 0,
+so that the construction
+
+ for i,v in ipairs(t) do ... end
+
+will iterate over the pairs (1,t[1]), (2,t[2]), ...,
+up to the first integer key with a nil value in the table.
+
+
See next for the caveats of modifying the table during its traversal.
+
+
load (func [, chunkname])
+
+
Loads a chunk using function func to get its pieces.
+Each call to func must return a string that concatenates
+with previous results.
+A return of nil (or no value) signals the end of the chunk.
+
+
If there are no errors,
+returns the compiled chunk as a function;
+otherwise, returns nil plus the error message.
+The environment of the returned function is the global environment.
+
+
chunkname is used as the chunk name for error messages
+and debug information.
+
+
loadfile ([filename])
+
+
Similar to load,
+but gets the chunk from file filename
+or from the standard input,
+if no file name is given.
+
+
loadstring (string [, chunkname])
+
+
Similar to load,
+but gets the chunk from the given string.
+
+
To load and run a given string, use the idiom
+
+ assert(loadstring(s))()
+
+
+
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.
+
+
Lua has no declaration of fields.
+There is no difference between a
+field not present in a table or a field with value nil.
+Therefore, next only considers fields with non-nil values.
+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 or the ipairs function.)
+
+
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)
+
+
Returns three values: the next function, the table t, and nil,
+so that the construction
+
+ for k,v in pairs(t) do ... end
+
+will iterate over all key--value pairs of table t.
+
+
See next for the caveats of modifying the table during its traversal.
+
+
pcall (f, arg1, arg2, ...)
+
+
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 (e1, e2, ...)
+Receives any number of arguments,
+and prints their values to stdout,
+using the tostring function to convert them to strings.
+print is not intended for formatted output,
+but only as a quick way to show a value,
+typically for debugging.
+For formatted output, use string.format.
+
+
rawequal (v1, v2)
+Checks whether v1 is equal to v2,
+without invoking any metamethod.
+Returns a boolean.
+
+
rawget (table, index)
+Gets the real value of table[index],
+without invoking any metamethod.
+table must be a table and
+index any value different from nil.
+
+
rawset (table, index, value)
+Sets the real value of table[index] to value,
+without invoking any metamethod.
+table must be a table,
+index any value different from nil,
+and value any Lua value.
+
+
select (index, ...)
+
+
If index is a number,
+returns all arguments after argument number index.
+Otherwise, index must be the string "#",
+and select returns the total number of extra arguments it received.
+
+
setfenv (f, table)
+
+
Sets the environment to be used by the given function.
+f can be a Lua function or a number
+that specifies the function at that stack level:
+Level 1 is the function calling setfenv.
+setfenv returns the given function.
+
+
As a special case, when f is 0 setfenv changes
+the environment of the running thread.
+In this case, setfenv returns no values.
+
+
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])
+Tries to convert its argument to a number.
+If the argument is already a number or a string convertible
+to a number, then tonumber returns this number;
+otherwise, it returns nil.
+
+
An optional argument specifies the base to interpret the numeral.
+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.
+In base 10 (the default), the number may have a decimal part,
+as well as an optional exponent part (see 2.1).
+In other bases, only unsigned integers are accepted.
+
+
tostring (e)
+Receives an argument of any type and
+converts it to a string in a reasonable format.
+For complete control of how numbers are converted,
+use string.format.
+
+
If the metatable of e has a "__tostring" field,
+then tostring calls the corresponding value
+with e as argument,
+and uses the result of the call as its result.
+
+
type (v)
+Returns the type of its only argument, coded as a string.
+The possible results of this function are
+"nil" (a string, not the value nil),
+"number",
+"string",
+"boolean,
+"table",
+"function",
+"thread",
+and "userdata".
+
+
unpack (list [, i [, j]])
+Returns the elements from the given table.
+This function is equivalent to
+
+ return list[i], list[i+1], ..., list[j]
+
+except that the above code can be written only for a fixed number
+of elements.
+By default, i is 1 and j is the length of the list,
+as defined by the length operator (see 2.5.5).
+
+
_VERSION
+A global variable (not a function) that
+holds a string containing the current interpreter version.
+The current contents of this variable is "Lua 5.1".
+
+
xpcall (f, err)
+
+
This function is similar to pcall,
+except that you can set a new error handler.
+
+
xpcall calls function f in protected mode,
+using err as the error handler.
+Any error inside f is not propagated;
+instead, xpcall catches the error,
+calls the err function with the original error object,
+and returns a status code.
+Its first result is the status code (a boolean),
+which is true if the call succeeds without errors.
+In this case, xpcall also returns all results from the call,
+after this first result.
+In case of any error,
+xpcall returns false plus the result from err.
+
+
5.2 - Coroutine Manipulation
+
+
The operations related to coroutines comprise a sub-library of
+the basic library and come inside the table coroutine.
+See 2.11 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, ..., valn])
+
+
Starts or continues the execution of coroutine co.
+The first time you resume a coroutine,
+it starts running its body.
+The values val1, ..., valn are passed
+as the arguments to the body function.
+If the coroutine has yielded,
+resume restarts it;
+the values val1, ..., valn 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,
+or nil when called by the main thread.
+
+
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 ([val1, ..., valn])
+
+
Suspends the execution of the calling coroutine.
+The coroutine cannot be running a C function,
+a metamethod, or an iterator.
+Any arguments to yield are passed as extra results to resume.
+
+
5.3 - Modules
+
+
The package library provides basic
+facilities for loading and building modules in Lua.
+It exports two of its functions directly in the global environment:
+require and module.
+Everything else is exported in a table package.
+
+
module (name [, ...])
+
+
Creates a module.
+If there is a table in package.loaded[name],
+this table is the module.
+Otherwise, if there is a global table t with the given name,
+this table is the module.
+Otherwise creates a new table t and
+sets it as the value of the global name and
+the value of package.loaded[name].
+This function also initializes t._NAME with the given name,
+t._M with the module (t itself),
+and t._PACKAGE with the package name
+(the full module name minus last component; see below).
+Finally, module sets t as the new environment
+of the current function and the new value of package.loaded[name],
+so that require returns t.
+
+
If name is a compound name
+(that is, one with components separated by dots),
+module creates (or reuses, if they already exist)
+tables for each component.
+For instance, if name is a.b.c,
+then module stores the module table in field c of
+field b of global a.
+
+
This function may receive optional options after
+the module name,
+where each option is a function to be applied over the module.
+
+
require (modname)
+
+
Loads the given module.
+The function starts by looking into the table package.loaded
+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,
+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 below).
+
+
When loading a C library,
+require first uses a dynamic link facility to link the
+application with the library.
+Then it tries to find a C function inside this 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.
+
+
If require finds neither a Lua library nor a
+C library for a module,
+it calls the all-in-one loader.
+This loader 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.
+
+
Once a loader is found,
+require calls the loader with a single argument, modname.
+If the loader returns any value,
+require assigns it to package.loaded[modname].
+If the loader returns no 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 signals an error.
+
+
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
+(plus another 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.
+
+
package.loadlib (libname, funcname)
+
+
Dynamically links the host program with the C library libname.
+Inside this library, looks for a function funcname
+and returns this function as a C function.
+(So, funcname must follow the protocol (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 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 ANSI 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 or
+with a default path defined in luaconf.h,
+if the environment variable is not defined.
+Any ";;" in the value of the environment variable
+is replaced by the default path.
+
+
A path is a sequence of templates separated by semicolons.
+For each template, require will change each interrogation
+mark in the template by filename,
+which is modname with each dot replaced by a
+"directory separator" (such as "/" in Unix);
+then it will try to load the resulting file name.
+So, for instance, if the Lua path is
+
+ "./?.lua;./?.lc;/usr/local/?/init.lua"
+
+the search for a Lua loader for module foo
+will try to load the files
+./foo.lua, ./foo.lc, and
+/usr/local/foo/init.lua, in that order.
+
+
package.preload
+
+
A table to store loaders for specific modules
+(see require).
+
+
package.seeall (module)
+
+
Sets a metatable for module with
+its __index field referring to the global environment,
+so that this module inherits values
+from the global environment.
+To be used as an option to function module.
+
+
5.4 - String Manipulation
+
+
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 metatable itself.
+Therefore, you can use the string functions in object-oriented style.
+For instance, string.byte(s, i)
+can be written as s:byte(i).
+
+
string.byte (s [, i [, j]])
+Returns the internal numerical codes of the characters s[i],
+s[i+1], ..., s[j].
+The default value for i is 1;
+the default value for j is i.
+
+
Note that numerical codes are not necessarily portable across platforms.
+
+
string.char (i1, i2, ...)
+Receives 0 or more integers.
+Returns a string with length equal to the number of arguments,
+in which each character has the internal numerical code equal
+to its corresponding argument.
+
+
Note that 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 loadstring on this string returns
+a copy of the function.
+function must be a Lua function without 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 may 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, e1, e2, ...)
+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 printf family of
+standard C functions.
+The only differences are that the options/modifiers
+*, l, L, n, p,
+and h are not supported
+and that there is an extra option, q.
+The q option formats a string in a form suitable to be safely read
+back by the Lua interpreter:
+The string is written between double quotes,
+and all double quotes, newlines, embedded zeros,
+and backslashes in the string
+are correctly escaped when written.
+For instance, the call
+
+ string.format('%q', 'a string with "quotes" and \n new line')
+
+will produce the string:
+
+"a string with \"quotes\" and \
+ new line"
+
+
+
The options c, d, E, e, f,
+g, G, i, o, u, X, and x all
+expect a number as argument,
+whereas q and s expect a string.
+
+
This function does not accept string values
+containing embedded zeros.
+
+
string.gmatch (s, pattern)
+Returns an iterator function that,
+each time it is called,
+returns the next captures from pattern over string s.
+
+
If pattern specifies no captures,
+then the whole match is produced in each call.
+
+
As an example, the following loop
+
+ s = "hello world from Lua"
+ for w in string.gmatch(s, "%a+") do
+ print(w)
+ end
+
+will iterate over all the words from string s,
+printing one per line.
+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
+
+
+
string.gsub (s, pattern, repl [, n])
+Returns a copy of s
+in which all occurrences of the pattern have been
+replaced by a replacement string specified by repl,
+which may be a string, a table, or a function.
+gsub also returns, as its second value,
+the total number of substitutions made.
+
+
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 %n,
+with n between 1 and 9,
+stands for the value of the n-th captured substring (see below).
+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 the pattern specifies no captures,
+then the whole match is used 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;
+if the pattern specifies no captures,
+then the whole match is passed as a sole argument.
+
+
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).
+
+
The optional last parameter n limits
+the maximum number of substitutions to occur.
+For instance, when n is 1 only the first occurrence of
+pattern is replaced.
+
+
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 loadstring(s)()
+ end)
+ --> x="4+5 = 9"
+
+ local t = {name="lua", version="5.1"}
+ x = string.gsub("$name%-$version.tar.gz", "%$(%w+)", t)
+ --> x="lua-5.1.tar.gz"
+
+
+
string.len (s)
+Receives a string and returns its length.
+The empty string "" has length 0.
+Embedded zeros are counted,
+so "a\000bc\000" has length 5.
+
+
string.lower (s)
+Receives a string and returns a copy of this string with all
+uppercase letters changed to lowercase.
+All other characters are left unchanged.
+The definition of what an uppercase letter is depends on the current locale.
+
+
string.match (s, pattern [, init])
+Looks for the first match of
+pattern in the string s.
+If it finds one, then match returns
+the captures from the pattern;
+otherwise it returns nil.
+If pattern specifies no captures,
+then the whole match is returned.
+A third, optional numerical argument init specifies
+where to start the search;
+its default value is 1 and may be negative.
+
+
string.rep (s, n)
+Returns a string that is the concatenation of n copies of
+the string s.
+
+
string.reverse (s)
+Returns a string that is the string s reversed.
+
+
string.sub (s, i [, j])
+Returns the substring of s that
+starts at i and continues until j;
+i and j may be negative.
+If j is absent, then it is assumed to be equal to -1
+(which is the same as the string length).
+In particular,
+the call string.sub(s,1,j) returns a prefix of s
+with length j,
+and string.sub(s, -i) returns a suffix of s
+with length i.
+
+
string.upper (s)
+Receives a string and returns a copy of this string with all
+lowercase letters changed to uppercase.
+All other characters are left unchanged.
+The definition of what a lowercase letter is depends on the current locale.
+
+
Patterns
+
+
+A character class is used to represent a set of characters.
+The following combinations are allowed in describing a character class:
+
+
x (where x is not one of the magic characters
+^$()%.[]*+-?)
+--- represents the character x itself.
+
. --- (a dot) represents all characters.
+
%a --- represents all letters.
+
%c --- represents all control characters.
+
%d --- represents all digits.
+
%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.
+
%z --- represents the character with representation 0.
+
%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 may be specified by
+separating the end characters of the range with a `-´.
+All classes %x described above may 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 may be
+
+
+a single character class,
+which matches any single character in the class;
+
+a single character class followed by `*´,
+which matches 0 or more repetitions of characters in the class.
+These repetition items will always match the longest possible sequence;
+
+a single character class followed by `+´,
+which matches 1 or more repetitions of characters in the class.
+These repetition items will always match the longest possible sequence;
+
+a single character class followed by `-´,
+which also matches 0 or more repetitions of characters in the class.
+Unlike `*´,
+these repetition items will always match the shortest possible sequence;
+
+a single character class followed by `?´,
+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.
+
+
+
+A pattern is a sequence of pattern items.
+A `^´ 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 may 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.
+
+
A pattern cannot contain embedded zeros. Use %z instead.
+
+
5.5 - Table Manipulation
+This library provides generic functions for table manipulation.
+It provides all its functions inside the table table.
+
+
Most functions in the table library assume that the table
+represents an array or a list.
+For these functions, when we talk about the "length" of a table
+we mean the result of the length operator.
+
+
table.concat (table [, sep [, i [, j]]])
+Returns table[i]..sep..table[i+1] ... sep..table[j].
+The default value for sep is the empty string,
+the default for i is 1,
+and the default for j is the length of the table.
+If i is greater than j, returns the empty string.
+
+
table.insert (table, [pos,] value)
+
+
Inserts element value at position pos in table,
+shifting up other elements to open space, if necessary.
+The default value for pos is n+1,
+where n is the length of the table (see 2.5.5),
+so that a call table.insert(t,x) inserts x at the end
+of table t.
+
+
table.maxn (table)
+
+
Returns the largest positive numerical index of the given table,
+or zero if the table has no positive numerical indices.
+(To do its job this function does a linear traversal of
+the whole table.)
+
+
table.remove (table [, pos])
+
+
Removes from table the element at position pos,
+shifting down other elements to close the space, if necessary.
+Returns the value of the removed element.
+The default value for pos is n,
+where n is the length of the table,
+so that a call table.remove(t) removes the last element
+of table t.
+
+
table.sort (table [, comp])
+Sorts table elements in a given order, in-place,
+from table[1] to table[n],
+where n is the length of the table.
+If comp is given,
+then it must be a function that receives two table elements,
+and returns true
+when the first is less than the second
+(so that not comp(a[i+1],a[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.
+
+
5.6 - Mathematical Functions
+
+
This library is an interface to the standard C math library.
+It provides all its functions inside the table math.
+The library provides the following functions:
+
+
+
+
+
+
+
+
+
+plus a variable math.pi and
+a variable math.huge,
+with the value HUGE_VAL.
+Most of these functions
+are only interfaces to the corresponding functions in the C library.
+All trigonometric functions work in radians.
+The functions math.deg and math.rad convert
+between radians and degrees.
+
+
The function math.max returns the maximum
+value of its numeric arguments.
+Similarly, math.min computes the minimum.
+Both can be used with 1, 2, or more arguments.
+
+
The function math.modf corresponds to the modf C function.
+It returns two values:
+The integral part and the fractional part of its argument.
+The function math.frexp also returns 2 values:
+The normalized fraction and the exponent of its argument.
+
+
The functions math.random and math.randomseed
+are interfaces to the simple random generator functions
+rand and srand that are provided by ANSI C.
+(No guarantees can be given for their statistical properties.)
+When called without arguments,
+math.random returns a pseudo-random real number
+in the range [0,1).
+When called with a number n,
+math.random returns
+a pseudo-random integer in the range [1,n].
+When called with two arguments,
+l and u,
+math.random returns a pseudo-random
+integer in the range [l,u].
+The math.randomseed function sets a "seed"
+for the pseudo-random generator:
+Equal seeds produce equal sequences of numbers.
+
+
5.7 - Input and Output Facilities
+
+
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.
+
+
Unless otherwise stated,
+all I/O functions return nil on failure
+(plus an error message as a second result)
+and some value different from nil on success.
+
+
io.close ([file])
+
+
Equivalent to file:close().
+Without a file, closes the default output file.
+
+
io.flush ()
+
+
Equivalent to file:flush over the default output file.
+
+
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,
+each time it is called,
+returns a new line from the file.
+Therefore, the construction
+
+ for line in io.lines(filename) do ... end
+
+will iterate over all lines of the 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() (without a 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.
+
+
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 may also have a `b´ at the end,
+which is needed in some systems to open the file in binary mode.
+This string is exactly what is used in the
+standard C function fopen.
+
+
io.output ([file])
+
+
Similar to io.input, but operates over the default output file.
+
+
io.popen ([prog [, mode]])
+
+
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").
+
+
This function is system dependent and is not available
+on all platforms.
+
+
io.read (format1, ...)
+
+
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 (value1, ...)
+
+
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.
+
+
file:flush ()
+
+
Saves any written data to file.
+
+
file:lines ()
+
+
Returns an iterator function that,
+each time it is called,
+returns a new line from the file.
+Therefore, the construction
+
+ for line in file:lines() do ... end
+
+will iterate over all lines of the file.
+(Unlike io.lines, this function does not close the file
+when the loop ends.)
+
+
file:read (format1, ...)
+
+
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 entire 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.
+
number reads a string with up to this number of characters,
+returning nil on end of file.
+If number is zero,
+it reads nothing and returns an empty string,
+or 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, function seek returns the final file position,
+measured in bytes from the beginning of the file.
+If this function 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 5.7)).
+
"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, sizes
+specifies the size of the buffer, in bytes.
+The default is an appropriate size.
+
+
file:write (value1, ...)
+
+
Writes the value of each of its arguments to
+the file.
+The arguments must be strings or numbers.
+To write other values,
+use tostring or string.format before write.
+
+
5.8 - Operating System Facilities
+
+
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 *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).
+
+
If format is not *t,
+then date returns the date as a string,
+formatted according to the same rules as the 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")).
+
+
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 C function system.
+It passes command to be executed by an operating system shell.
+It returns a status code, which is system-dependent.
+If command is absent, then it returns nonzero if a shell is available
+and zero otherwise.
+
+
os.exit ([code])
+
+
Calls the C function exit,
+with an optional code,
+to terminate the host program.
+The default value for code is the success code.
+
+
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 directory with the given name.
+Directories must be empty to be removed.
+If this function fails, it returns nil,
+plus a string describing the error.
+
+
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.
+
+
os.setlocale (locale [, category])
+
+
Sets the current locale of the program.
+locale is a 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.
+
+
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, min, sec, and isdst
+(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
+date and 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.
+
+
5.9 - The Debug Library
+
+
This library provides
+the functionality of the debug interface to Lua programs.
+You should exert care when using this library.
+The functions provided here should be used exclusively for debugging
+and similar tasks, such as profiling.
+Please resist the temptation to use them as a
+usual programming tool:
+They can be very slow.
+Moreover, several of its functions
+violate some assumptions about Lua code
+(e.g., that variables local to a function
+cannot be accessed from outside or
+that userdata metatables cannot be changed by Lua code)
+and therefore can compromise otherwise secure code.
+
+
All functions in this library are provided
+inside the debug table.
+
+
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.getfenv (o)
+Returns the environment of object o.
+
+
debug.gethook ()
+
+
Returns the current hook settings, 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 (function [, 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 function,
+which means the function running at level function of the call stack:
+Level 0 is the current function (getinfo itself);
+level 1 is the function that called getinfo;
+and so on.
+If function is a number larger than the number of active functions,
+then getinfo returns nil.
+
+
The returned table contains 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.
+If present,
+the option `f´
+adds a field named func with the function itself.
+
+
For instance, the expression debug.getinfo(1,"n").name returns
+a name of the current function, if a reasonable name can be found,
+and debug.getinfo(print) returns a table with all available information
+about the print function.
+
+
debug.getlocal (level, local)
+
+
This function returns the name and the value of the local variable
+with index local of the function at level level of the stack.
+(The first parameter or local variable has index 1, and so on,
+until the last active local variable.)
+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 debug.getinfo to check whether the level is valid.)
+
+
Variable names starting with `(´ (open parentheses)
+represent internal variables
+(loop control variables, temporaries, and C function locals).
+
+
debug.getmetatable (object)
+
+
Returns the metatable of the given object
+or nil if it does not have a metatable.
+
+
This function returns the name and the value of the upvalue
+with index up of the function func.
+The function returns nil if there is no upvalue with the given index.
+
+
debug.setfenv (object, table)
+
+
Sets the environment of the given object to the given table.
+
+
debug.sethook (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", "return" (or "tail 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),
+unless the event is "tail return".
+In this case, Lua is only simulating the return,
+and a call to getinfo will return invalid data.
+
+
debug.setlocal (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.
+
+
debug.setmetatable (object, table)
+
+
Sets the metatable for the given object to the given table
+(which can be nil).
+
+
debug.setupvalue (func, up, value)
+
+
This function assigns the value value to the upvalue
+with index up of the function func.
+The function returns nil if there is no upvalue
+with the given index.
+Otherwise, it returns the name of the upvalue.
+
+
debug.traceback ([message])
+
+
Returns a string with a traceback of the call stack.
+An optional message string is appended
+at the beginning of the traceback.
+This function is typically used with xpcall to produce
+better error messages.
+
+
+
6 - Lua Stand-alone
+
+
Although Lua has been designed as an extension language,
+to be embedded in a host C program,
+it is also frequently used as a stand-alone language.
+An interpreter for Lua as a stand-alone language,
+called simply lua,
+is provided with the standard distribution.
+The stand-alone interpreter includes
+all standard libraries, including the debug library.
+Its usage is:
+
+ lua [options] [script [args]]
+
+The options are:
+
+
-estat executes string stat;
+
-lmod "requires" mod;
+
-i enters interactive mode after running script;
+
-v prints version information;
+
-- 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.
+
+
Before running any argument,
+the interpreter checks for an environment variable LUA_INIT.
+If its format is @filename,
+then lua executes the file.
+Otherwise, lua executes the string itself.
+
+
All options are handled in order, except -i.
+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 (which is `1´),
+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
+
+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.
+
+
If the global variable _PROMPT contains a string,
+then its value is used as the prompt.
+Similarly, if the global variable _PROMPT2 contains a string,
+its value is used as the secondary prompt
+(issued during incomplete statements).
+Therefore, both prompts can be changed directly on the command line.
+For instance,
+
+ $ lua -e"_PROMPT='myprompt> '" -i
+
+(the outer pair of quotes is for the shell,
+the inner pair is for Lua),
+or in any Lua programs by assigning to _PROMPT.
+Note the use of -i to enter interactive mode; otherwise,
+the program would just end silently right after the assignment to _PROMPT.
+
+
To allow the use of Lua as a
+script interpreter in Unix systems,
+the stand-alone 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.)
+
+
+
+
Incompatibilities with the Previous Version
+
+
+
Here we list the incompatibilities that may be found when moving a program
+from Lua 5.0 to Lua 5.1.
+You can avoid most of the incompatibilities compiling Lua with
+appropriate options (see file luaconf.h).
+However,
+all these compatibility options will be removed in the next version of Lua.
+
+
Incompatibilities with version 5.0
+
+
Changes in the Language
+
+
+The vararg system changed from the pseudo-argument arg with a
+table with the extra arguments to the vararg expression.
+(Option LUA_COMPAT_VARARG in luaconf.h.)
+
+
+There was a subtle change in the scope of the implicit
+variables of the for statement and for the repeat statement.
+
+
+The long string/long comment syntax ([[...]]) does not allow nesting.
+You can use the new syntax ([=[...]=]) in these cases.
+(Option LUA_COMPAT_LSTR in luaconf.h.)
+
+
+
+
Changes in the Libraries
+
+
+
+Function string.gfind was renamed string.gmatch.
+(Option LUA_COMPAT_GFIND)
+
+
+When string.gsub is called with a function as its
+third argument,
+whenever this function returns nil or false the
+replacement string is the whole match,
+instead of the empty string.
+
+
+Function table.setn was deprecated.
+Function table.getn corresponds
+to the new length operator (#);
+use the operator instead of the function.
+(Option LUA_COMPAT_GETN)
+
+
+Function loadlib was renamed package.loadlib.
+(Option LUA_COMPAT_LOADLIB)
+
+
+Function math.mod was renamed math.fmod.
+(Option LUA_COMPAT_MOD)
+
+
+Functions table.foreach and table.foreachi are deprecated.
+You can use a for loop with pairs or ipairs instead.
+
+
+There were substantial changes in function require due to
+the new module system.
+However, the new behavior is mostly compatible with the old,
+but require gets the path from package.path instead
+of from LUA_PATH.
+
+
+Function collectgarbage has different arguments.
+Function gcinfo is deprecated;
+use collectgarbage("count") instead.
+
+
+
+
Changes in the API
+
+
+
+The luaopen_* functions (to open libraries)
+cannot be called directly,
+like a regular C function.
+They must be called through Lua,
+like a Lua function.
+
+
+Function lua_open was replaced by lua_newstate to
+allow the user to set a memory allocation function.
+You can use luaL_newstate from the standard library to
+create a state with a standard allocation function
+(based on realloc).
+
+
+Functions luaL_getn and luaL_setn
+(from the auxiliary library) are deprecated.
+Use lua_objlen instead of luaL_getn
+and nothing instead of luaL_setn.
+
+
+Function luaL_openlib was replaced by luaL_register.
+
+
+
+
+
+
The Complete Syntax of Lua
+
+
+
Here is the complete syntax of Lua in extended BNF.
+It does not describe operator priorities or some syntactical restrictions,
+such as return and break statements
+can only appear as the last statement of a block.
+
+
+
+
+
+ chunk ::= {stat [`;´]} [laststat[`;´]]
+
+ block ::= chunk
+
+ stat ::= varlist1 `=´ explist1 |
+ functioncall |
+ 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 explist1 do block end |
+ function funcname funcbody |
+ localfunction Name funcbody |
+ local namelist [`=´ explist1]
+
+ laststat ::= return [explist1] | break
+
+ funcname ::= Name {`.´ Name} [`:´ Name]
+
+ varlist1 ::= var {`,´ var}
+
+ var ::= Name | prefixexp `[´ exp `]´ | prefixexp `.´ Name
+
+ namelist ::= Name {`,´ Name}
+
+ explist1 ::= {exp `,´} exp
+
+ exp ::= nil | false | true | Number | String | `...´ |
+ function | prefixexp | tableconstructor | exp binop exp | unop exp
+
+ prefixexp ::= var | functioncall | `(´ exp `)´
+
+ functioncall ::= prefixexp args | prefixexp `:´ Name args
+
+ args ::= `(´ [explist1] `)´ | tableconstructor | String
+
+ function ::= function funcbody
+
+ funcbody ::= `(´ [parlist1] `)´ block end
+
+ parlist1 ::= namelist [`,´ `...´] | `...´
+
+ tableconstructor ::= `{´ [fieldlist] `}´
+
+ fieldlist ::= field {fieldsep field} [fieldsep]
+
+ field ::= `[´ exp `]´ `=´ exp | Name `=´ exp | exp
+
+ fieldsep ::= `,´ | `;´
+
+ binop ::= `+´ | `-´ | `*´ | `/´ | `^´ | `%´ | `..´ |
+ `<´ | `<=´ | `>´ | `>=´ | `==´ | `~=´ |
+ and | or
+
+ unop ::= `-´ | not | `#´
+
+
+Lua 5.1 Reference Manual
+