How To Lua Code
How To Lua Code
Lua C Script
How To Lua Code In Roblox

Today I show you guys how to convert a simple Lua script to Lua C.My discord:https://discord.me/bditt. The syntax of an if.else statement in Lua programming language is −. If (booleanexpression) then - statement (s) will execute if the boolean expression is true - else - statement (s) will execute if the boolean expression is false - end. If the Boolean expression evaluates to true, then the if block of code will be executed, otherwise else block of code will be executed. Welcome to my second video on my channel!DownloadUPDATED: https://www.mediafire.com/folder/zaa568sq9enfk/LuaConverterVirusTotal:https://www.virustotal.com.

EDIT: Part 2

Long time without posting, busy at work, family, etc.

Today I decided to write a bit on Lua and how to integrate it with C++.

Lua is a scripting language with an emphasis on being easily embeddable. Lua isused as the scripting language in Photoshop CS, and World of Warcraft, forexample. So if you are looking into adding scriptability to your C or C++applications Lua is quite suited for the task.

In order to learn Lua (both the language itself and how to embed it into yourapp) I recommend you Programming in Luaby one of the Luaauthors.

You can find tons of tutorials on how to get started with Lua. So I will focushere on how to integrate with C++. Most of the sources I’ve found about Lua -C++ integrations take the approach of frameworks to automatically wrap yourobjects/classes to be usable from within Lua. I find this approach confusing, Ithink it’s better to learn how to do it manually, and that’s what I will dohere.

Step 0. Compile Lua itself

Download Lua 5.2.1 and compile it. Usually it enough with make macosx ormake linux. That will generate liblua.a, the library that we will link to.

Step 1. Create a simple host app

We need a simple host app. Our host app will simply setup Lua and run a scriptfrom it. This script will have access to a std::queue from the host app. Thiswill illustrate how you can share objects with the Lua part. Later we will takea more complex example.

Let’s start with the basic skeleton of a lua environment with somecommunication with its host:

The Makefile

It uses LUAHOME that should point to the directory containing both liblua.a and the lua*.h files.

The samplehost application

The Lua script

The code explained step by step:

Initialization

That creates a lua_State loads the standard libs in it and also loads the code in luascript.lua.

Adding variables from C++ into Lua

Then it sets a global variable in Lua from C++ code using lua_setglobal. Ifyou don’t know what are the lua_pushxxxx and the Lua stack, etc. I recomentthat you take a look at the Lua Reference Manual and Programming in Lua.More or less Lua and the C++ communicate through the stack that livesin lua_State and there is bunch of function to manipulate that stack. So inorder to set a global in Lua from C++ you must push the value into the stackand call lua_setglobal that will pop the value in the stack and assign it tothe identifier provided inside the Lua environment.

After setting the global cppvar it executes the loaded chunk of code (that is in the stack) with lua_pcall. The Lua code is able to read and print the value of cppvar. The lua code will also set a new global luavar that we will access from C++.

How To Lua Code

Reading a Lua variable from C++

To get luavar from C++, we must first use lua_getglobal that will put the value associated with the identifier into the top of the stack and the lua_tonumber will transform whatever it’s at the top of the stack into a double (well a luaNumber) and then we can use that double in our C++ code to print it.

Calling a Lua function from C++

The example won’t be complete without function calling so that’s the next step.Calling a Lua function from C++ it’s quite easy. Function in Lua are firstclass values, so that means that it’s just a like reading a any other value.lua_getglobal will get the value and put it on the stack and then we push thefunction arguments into the stack and use lua_pcall to call the function(that is the stack). The returned value from the function will be pushed in thestack and that’s were the C++ code will get it, lua_tostring and then it willremove from the stack with lua_pop.

Calling a C++ function from Lua

The other way around it’s more complex. You can’t just call any function fromLua. It has to has a special signature lua_CFunction, that is, typedef int(*lua_CFunction) (lua_State *L) a function that returns an int and takes alua_State. This special funciton will communicate with Lua via the lua stackthat resides in the lua_State parameter. The return value of the functiontell lua how many value the function has pushed into the stack as result valuesfor the function call.

So to make the function accesible from Lua, you create push the function intothe stack with lua_pushcfunction and bind it to an identifier in lua withlua_setglobal. Then lua code will be able to invoke this function like anyother function. In the example I call the myfunction (which is lua code) andmyfunction in turn invokes cppfunction which is “bound” to C++l_cppfunction. Ah, I almost forgot. l_cppfunction is declared as extern'C' telling the compiler to provide C linkage for this function so it can becalled from a C library like Lua is.

Free Lua resources

lua_close will free all resources held by the lua_State L.

Wrap up

I will leave the part on how to wrap C++ class objects inLua for a later post because Idon’t want to make this post too long. Hopefully I’ll post it tomorrow.

The lua source can be found at the lua website here. We'll be using the latest version, 5.2.3 (though other recent versions of Lua will behave similarly).

Once you have the latest lua source, it's time to build it. (Yes, you could just download header files and the .dll, but what's the fun in that? When available, it's always better to have the source, that way you can see how things are really working -- and you can debug more easily). Using visual studio:

Open up Visual Studio, and create a new project

Create a win 32 console application
In the Project Creation wizard, check the 'static library' radio button to build as a static library.

Add the lua source to the project. Just dragging the files directly from their folders into the project works well for this.
There are two source files that you don't need: lua.c and luac.c. These files contain the main program for the command line interpreter and the bytecode compiler, respectively. You can remove this files from the project if you wish. If you are building as a static library, having more than one main won't be a problem. However, if you are building as an executable, then you will need to exclude one of these files from the project. Right-click on them in the project explorer and select 'Exclude from Project'

You now have a project that you can add to any solution that needs lua. Once you have added the lua project to your game, you need to do a few more steps:

In the properties for the project that is using lua, be sure that the directory that contains the lua .h files is included in the set of include paths. If at all possible, make these paths relative, and not absolute
Your project will need to get at the .lib files for the lua. There are a few ways to do this:
- Add a reference from your project to the lua project. Right-click on your project in the project explorer, and select References:
  Add a new reference:
  Select the lua project:
- Or, add Lua.lib to 'Additional Dependencies' (in the Librarian/Genrerl tab of the Project Property Pages) and add the directory where Lua.lib lives to 'Additional Library Directories' (also in the Librarian/Genrerl tab of the Project Property Pages).

Once we have build Lua, and set up our project dependencies correctly, we are ready to use in on our application,

First off, we need to include the proper header files. Since Lu