Calling Lua function from C + +

http://blog.csdn.net/cnjet/article/details/5909519

Calling Lua function from C + + is very simple. Value passing between C + + Lua goes through stack, LUA C API provides a convenience ways for the call Lua function f Rom C. To call Lua function, you need to specify:

1. Function Name.
2. Parameters of function call.
3. Return values expected (Lua function support multiple results reture)

Let say my Lua function name is call F in Last.lua, takes 2 parameters.

-- last.luafunction f (x, y)    return (x^2 * math.sin(y))/(1 - x)end

I perform function call from C + + like this:

01

//last.cc

02	# extern "C" {

03	# #include "lua.h"

04	# #include "lualib.h"

05	# #include "lauxlib.h"

06

# }

07

08

intmain()

09

{

10

doublez;

11	lua_State *L = lua_open();

12	luaL_openlibs(L);

13	if(luaL_loadfile(L, "last.lua") || lua_pcall(L, 0, 0, 0)) {

14	printf("error: %s", lua_tostring(L, -1));

15

return-1;

16

}

17

18	lua_getglobal(L, "f");

19	if(!lua_isfunction(L,-1))

20

{

21	lua_pop(L,1);

22

return-1;

23

}

24	lua_pushnumber(L, 21);   /* push 1st argument */

25	lua_pushnumber(L, 31);   /* push 2nd argument */

26

27	/* do the call (2 arguments, 1 result) */

28	if(lua_pcall(L, 2, 1, 0) != 0) {

29	printf("error running function `f‘: %s/n",lua_tostring(L, -1));

30

return-1;

31

}

32

33	/* retrieve result */

34	if(!lua_isnumber(L, -1)) {

35	printf("function `f‘ must return a number/n");

36

return-1;

37

}

38	z = lua_tonumber(L, -1);

39	printf("Result: %f/n",z);

40	lua_pop(L, 1);

41	lua_close(L);

42

43

return0;

44

}

Compile it with g++ like this:

g++ -o last{,.cc} -llua -ldl

The results:

Result: -12.158958

Brief explanation of the C + + codes above:
First, I trigger lua_getglobal to get the function name, then I-Push 2 parameters to stack. I make lua_pcall by telling Lua I has 2 params and expect 1 value return. Upon success, I retrieve the return value from the top of the stack.

Calling Lua function from C + +