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Date: Wed, 2 Jan 2013 10:46:13 -0800 (PST)
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Subject: Please help with my lua binding
From: Patrick <patrick@spellingbeewinnars.org>
Injection-Date: Wed, 02 Jan 2013 18:46:13 +0000
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Date: 2013-01-02T10:46:13-08:00
List-Id: <comp.lang.ada>

Hello Everyone

I am trying to make a binding to Lua. 

Although I had to comment out a couple of functions, I have three compiling spec files for the three lua headers that are needed to form a binding.

I have a great free pascal binding to use as an example

I used fdump-ada-spec-slim and it helped a lot. I was able to sort out most of the types and macros by hand.

In lua, lua_State holds the instance of lua. It is an empty struct in the header and fdump skips it.

I don't really know how to represent this structure in lua.

I tried to define it as:

type lua_State is access lua_State;
pragma Import (C, lua_State, "lua_State");

 but when I call it in this piece of code:

with lauxlib_h ; use lauxlib_h ;
with lualib_h ; use lualib_h ;
with lua_h ; use lua_h ;


procedure test is
result : Integer ;
type L is access lua_State ;


begin

L := luaL_newstate ;
 
end test ;

I get this:
test.adb:27:01: invalid use of subtype mark in expression or call
lua_h.ads:149:26: type "lua_State" cannot be used before end of its declaration
lua_h.ads:150:19: second argument of pragma "import" must be object or subprogram
gnatmake: "test.adb" compilation error

In the pascal biding lua_State is:
Plua_State = Pointer;

They put a P at the start to show it is a pointer.

An example of it's use in C is:
int main(void)
{
    
lua_State *L;
L = luaL_newstate();  /* Create Lua state variable */
luaL_openlibs(L);     /* Load Lua libraries */
continues....

interfaces.C helps me a lot but outside of it I get mixed up working with C. Does anyone have any hints on how I could define lua_State in my spec file?

Thanks for reading.