mylib.c

/// A sample C extension.
// Demonstrates using ldoc's C/C++ support. Can either use /// or /*** */ etc.
// @module mylib
#include <string.h>
#include <math.h>

// includes for Lua
#include <lua.h>
#include <lauxlib.h>
#include <lualib.h>

/***
Create a table with given array and hash slots.
@function createtable
@param narr initial array slots, default 0
@param nrec initial hash slots, default 0
*/
static int l_createtable (lua_State *L) {
  int narr = luaL_optint(L,1,0);
  int nrec = luaL_optint(L,2,0);
  lua_createtable(L,narr,nrec);
  return 1;
}

/***
Solve a quadratic equation.
@function solve
@tparam num a coefficient of x^2
@tparam num b coefficient of x
@tparam num c constant
@treturn num first root
@treturn num second root
*/
static int l_solve (lua_State *L) {
    double a = lua_tonumber(L,1);  // coeff of x*x
    double b = lua_tonumber(L,2);  // coef of x
    double c = lua_tonumber(L,3);  // constant
    double abc = b*b - 4*a*c;
    if (abc < 0.0) {
        lua_pushnil(L);
        lua_pushstring(L,"imaginary roots!");
        return 2;
    } else {
        abc = sqrt(abc);
        a = 2*a;
        lua_pushnumber(L,(-b + abc)/a);
        lua_pushnumber(L,(+b - abc)/a);
        return 2;
    }
}

static const luaL_Reg mylib[] = {
    {"createtable",l_createtable},
    {"solve",l_solve},
    {NULL,NULL}
};

int luaopen_mylib(lua_State *L)
{
    luaL_register (L, "mylib", mylib);
    return 1;
}