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This page describes how, on Windows10, a new LUA module written in C can be added to V-REP.
V-REP uses version 5.1 of LUA but do not provide the files for development. So we first need to install our own LUA interpreter and then we show how to build an additional LUA module written in C.

==== 1 - Installing LUA ====

All versions of LUA can be downloaded from .
The code is [[https://www.lua.org/ftp/lua-5.1.5.tar.gz|downloaded]] and decompressed, this should give a folder called ** lua-5.1.5**. A batch file **build.cmd** is used to build the LUA interpreter and libraries. It is a modified version of the [[http://lua-users.org/wiki/BuildingLuaInWindowsForNewbies| original build.cmd file]].
<code bat>
@echo off
:: ========================
:: file build.cmd
:: ========================
setlocal
:: you may change the following variable's value
:: to suit the downloaded version
set lua_version=5.1.5

set work_dir=%~dp0
:: Removes trailing backslash
:: to enhance readability in the following steps
set work_dir=%work_dir:~0,-1%
set lua_install_dir=c:\lua
set compiler_bin_dir=c:\TDM-GCC-64\bin
set lua_build_dir=%work_dir%\lua-%lua_version%
set path=%compiler_bin_dir%;%path%

cd /D %lua_build_dir%
mingw32-make PLAT=mingw

echo.
echo **** COMPILATION TERMINATED ****
echo.
echo **** BUILDING BINARY DISTRIBUTION ****
echo.

:: create a clean "binary" installation
mkdir %lua_install_dir%
mkdir %lua_install_dir%\doc
mkdir %lua_install_dir%\bin
mkdir %lua_install_dir%\lib
mkdir %lua_install_dir%\include

copy %lua_build_dir%\doc\*.* %lua_install_dir%\doc\*.*
copy %lua_build_dir%\src\*.exe %lua_install_dir%\bin\*.*
copy %lua_build_dir%\src\*.dll %lua_install_dir%\bin\*.*
copy %lua_build_dir%\src\luaconf.h %lua_install_dir%\include\*.*
copy %lua_build_dir%\src\lua.h %lua_install_dir%\include\*.*
copy %lua_build_dir%\src\lualib.h %lua_install_dir%\include\*.*
copy %lua_build_dir%\src\lauxlib.h %lua_install_dir%\include\*.*
::copy %lua_build_dir%\src\lua.hpp %lua_install_dir%\include\*.*
copy %lua_build_dir%\src\liblua.a %lua_install_dir%\lib\*.*
copy %lua_install_dir%\bin\lua51.dll %lua_install_dir%\lib\liblua51.dll

echo.
echo **** BINARY DISTRIBUTION BUILT ****
echo.

%lua_install_dir%\bin\lua.exe -e"print [[Hello!]];print[[Simple Lua test successful!!!]]"

echo.

pause
</code>
This code has to be modified depending on where your c compiler is and where you want LUA to be installed.
In the file **lua-5.1.5\src\Makefile**, the comment at end of line 51 should be moved to another place, for example :
<code Makefile>
$(LUA_A): $(CORE_O) $(LIB_O)
	$(AR) $@ $(CORE_O) $(LIB_O)   # DLL needs all object files	
	$(RANLIB) $@
</code>
can be changed in :
<code Makefile>
# DLL needs all object files
$(LUA_A): $(CORE_O) $(LIB_O)
	$(AR) $@ $(CORE_O) $(LIB_O)	
	$(RANLIB) $@
</code>

At the end of the execution of the build command, the following text should appear :
<code bash>
C:\Users\Me>build
…
Hello!
Simple Lua test successful!!!

Press any key to continue . . .
</code>

The **path** environment variable can be set to use directly the LUA interpreter :
<code batch>
C:\Users\Me>setx path "%path%;c:\lua\bin"
</code>
Then the LUA interpreter can be simply used by typing **lua** in the command line :
<code batch>
C:\Users\Me>lua
Lua 5.1.5  Copyright (C) 1994-2012 Lua.org, PUC-Rio
> a=2
> b=3
> print (a*b)
6
> ^C
C:\Users\Me>
</code>
To quit, type Ctrl-C.


==== 2 - Installing "pack" module ====

Many LUA additional modules can be found [[http://webserver2.tecgraf.puc-rio.br/~lhf/ftp/lua/|here]]
First we get the source code of [[http://webserver2.tecgraf.puc-rio.br/~lhf/ftp/lua/5.1/lpack.tar.gz|lpack]]
 module for LUA 5.1 and decompress it.
A new **Makefile** is defined as follows : 
<code Makefile>
LUA_DIR=c:\lua
LUA_LIBDIR=$(LUA_DIR)\lib
LUA_INCDIR=$(LUA_DIR)\include
LIBFLAG= -shared 
RM= del

all: test

lpack.o: lpack.c
	gcc -I$(LUA_INCDIR) -c lpack.c

pack.dll: lpack.o
	gcc -o pack.dll $(LIBFLAG) lpack.o -L$(LUA_LIBDIR) -llua51

clean:
	$(RM) pack.dll lpack.o

test: pack.dll test.lua
	lua test.lua
</code> 

Then, we build and test the **pack** module using this new **Makefile** :
<code batch>
C:\Users\Me\pack>mingw32-make PLAT=mingw
gcc -Ic:\lua\include -c lpack.c
gcc -o pack.dll -shared  lpack.o -Lc:\lua\lib -llua51
lua test.lua
1B4C75615100010404040800        12
false   12
13      27      Lua     81      0       1       4       8       4       8       0
A1B0B91212B9B0A1A1B0B912
13      314159265       314159265       314159265
F1D4C853FB210940400921FB53C8D4F1F1D4C853FB210940
25      3.14159265      3.14159265      3.14159265
</code>

The last thing to do is to copy the module in the V-REP folder :
<code batch>
C:\Users\Me\pack>copy pack.dll "c:\Program Files\V-REP3\V-REP_PRO_EDU\"
</code>

==== 2 - useful links ====

Here are some useful links used to add LUA modules to V-REP.

  * IDE : [[https://downloads.codelite.org/|codelite]] and it's [[https://wiki.codelite.org/pmwiki.php#toc3||wiki]]
  * gcc compiler : [[https://jmeubank.github.io/tdm-gcc/|TDM-GCC 9.2.0]]
  * decompress tar.gz : [[https://www.7-zip.org/download.html|7zip]] 
  * creating a DLL : [[http://mingw.org/wiki/sampleDLL|mingw example]]
  * installing LUA on Windows :[[http://lua-users.org/wiki/BuildingLuaInWindowsForNewbies|lua-users.org wiki]] 
  * command line arguments :[[https://stackoverflow.com/questions/5034076/what-does-dp0-mean-and-how-does-it-work|parameters explained]]
  * Alternate gcc compiler (not used) : [[http://mingw-w64.org/doku.php|mingw-w64]] and how to  [[https://ascend4.org/Setting_up_a_MinGW-w64_build_environment#MinGW-w64|setup]]
  * simple LUA module : [[https://github.com/norman/hello-lua|hello world!]]
  * adding functionalities to LUA : [[http://webserver2.tecgraf.puc-rio.br/~lhf/ftp/lua/|list of modules]]