c-exercises/lua-foo.c

/*
 * Based on:
 *
 * http://heavycoder.com/tutorials/lua_embed.php
 * http://www.lua.org/pil/26.html
 * http://cc.byexamples.com/2008/06/07/how-to-embed-lua-51-in-c/
 *
 */

#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>

#include <lua.h>
#include <lualib.h>
#include <lauxlib.h>

#include <math.h>

void error(lua_State *L, const char *fmt, ...) {
  va_list argp;
  va_start(argp, fmt);
  vfprintf(stderr, fmt, argp);
  va_end(argp);
  lua_close(L);
  exit(EXIT_FAILURE);
}

/* Provided to Lua as 'mysin' later. */
static int l_mysin(lua_State *L) {
  double d = luaL_checknumber(L, 1);  /* get argument */

  lua_pushnumber(L, sin(d));  /* push result */
  return 1;  /* number of results */
}

int main(void) {
  /* Set up Lua. */
  lua_State *L;
  L = luaL_newstate();

  /* Load necessary libs. */
  luaL_Reg lualibs[] = {
    { "base", luaopen_base },
    { "string", luaopen_string },
    { NULL, NULL}
  };
  for(luaL_Reg *lib = lualibs; lib->func; lib++) {
    printf("Loading %s\n", lib->name);
    lib->func(L);
    lua_setglobal(L, lib->name);
    lua_settop(L, 0);
  }
  /* Alternatively, we could have called LuaL_openlibs(L) but that would have
     loaded *all* libs. */

  /* Register 'mysin'. */
  lua_pushcfunction(L, l_mysin);
  lua_setglobal(L, "mysin");

  /* Load and run Lua file. */
  const char* filename = "lua-foo.lua";
  if (luaL_loadfile(L, filename) || lua_pcall(L, 0, 0, 0))
    error(L, "cannot run file: %s\n", lua_tostring(L, -1));

  /* Clean up. */
  lua_close(L);

  /* Quit. */
  exit(EXIT_SUCCESS);
}