Re: Simple Function Call From C language

[Sean Conner <sean@...>]

It was thus said that the Great Austin Einter once stated:
> Hi
> Thanks a lot. Referring your links I could do a small test program. However
> I am not able to get the output of lua function in C code. Here is my
> example code. Please let me know, how to collect the lua function output in
> C code.  After I call lua_loadstring, I want to print function output in
> Code.., please let me know how to do it...

#include <stdio.h>
#include <stdlib.h>
#include <lua.h>
#include <lualib.h>
#include <lualib.h>

const char *c_function = "function fact(n) if n == 0 then return 1 else return n * fact(n-1) end end"

int main(void)
{
  lua_State *L;
  int        r;

  L = luaL_newstate();
  luaL_openlibs(L); /* open all built-in Lua libraries */

  /*------------------------------------------------------------------------
  ; the following two lines are basically luaL_dostring().  The first line
  ; compiles the given Lua code into Lua bytecode and returns the result on
  ; the Lua stack (not to be confused with the C stack---they are
  ; different).  For the example above, the resulting code needs to be
  ; executed to defien the fact() function.  Since luaL_loadstring() returns
  ; the compiled code on the Lua stack, we can simply call lua_pcall() to
  ; execute it.
  ;
  ; You might think that the function fact() will be defined at this point,
  ; but no, all that's been done by luaL_loadstring() is to generate the
  ; code that will define the fact() function.
  ;------------------------------------------------------------------------*/

  luaL_loadstring(L,c_function);
  lua_pcall(L,0,0,0);

  /*-----------------------------------------------------------------------
  ; now that we have fact() defined, we can now call it.  This just follows
  ; the example given for the description of lua_call() in the manual.
  ;----------------------------------------------------------------------*/

  lua_getglobal(L,"fact");	/* this is our function, defined globally */
  lua_pushinteger(L,4);		/* this call fact(4)			*/
  lua_call(L,1,1);		/* call fact, with one argument, and expect one result */

  r = luaL_checkinteger(L,-1);	/* the top of the Lua stack should contain our result */
  printf("Factorial: %d",r);
  
  lua_close(L);
  return EXIT_SUCCESS;
}

  -spc