nlua_rnd.c

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/*
 * See Licensing and Copyright notice in naev.h
 */
#include <lauxlib.h>
#include <math.h>
 
#include "nlua_rnd.h"
 
#include "nluadef.h"
#include "rng.h"
 
/* Random methods. */
static int rndL_int( lua_State *L );
static int rndL_sigma( lua_State *L );
static int rndL_twosigma( lua_State *L );
static int rndL_threesigma( lua_State *L );
static int rndL_uniform( lua_State *L );
static int rndL_angle( lua_State *L );
static int rndL_permutation( lua_State *L );
 
static const luaL_Reg rnd_methods[] = { { "rnd", rndL_int },
                                        { "sigma", rndL_sigma },
                                        { "twosigma", rndL_twosigma },
                                        { "threesigma", rndL_threesigma },
                                        { "uniform", rndL_uniform },
                                        { "angle", rndL_angle },
                                        { "permutation", rndL_permutation },
                                        { 0, 0 } }; 

int nlua_loadRnd( nlua_env env )
{
   nlua_register( env, "rnd", rnd_methods, 0 );
   return 0;
}

static int rndL_int( lua_State *L )
{
   int l, h;
   int o = lua_gettop( L );
 
   if ( o == 0 )
      lua_pushnumber( L, RNGF() ); /* random double 0 <= x <= 1 */
   else if ( o == 1 ) {            /* random int 0 <= x <= parameter */
      l = luaL_checkint( L, 1 );
      lua_pushnumber( L, RNG( 0, l ) );
   } else if ( o >= 2 ) { /* random int parameter 1 <= x <= parameter 2 */
      l = luaL_checkint( L, 1 );
      h = luaL_checkint( L, 2 );
      lua_pushnumber( L, RNG( l, h ) );
   } else
      NLUA_INVALID_PARAMETER( L, 1 );
 
   return 1; /* unless it's returned 0 already it'll always return a parameter
              */
}

static int rndL_sigma( lua_State *L )
{
   lua_pushnumber( L, RNG_1SIGMA() );
   return 1;
}

static int rndL_twosigma( lua_State *L )
{
   lua_pushnumber( L, RNG_2SIGMA() );
   return 1;
}

static int rndL_threesigma( lua_State *L )
{
   lua_pushnumber( L, RNG_3SIGMA() );
   return 1;
}

static int rndL_uniform( lua_State *L )
{
   int o = lua_gettop( L );
 
   if ( o == 0 )
      lua_pushnumber( L, RNGF() ); /* random double 0 <= x <= 1 */
   else if ( o == 1 ) {            /* random int 0 <= x <= parameter */
      int l = luaL_checknumber( L, 1 );
      lua_pushnumber( L, RNGF() * l );
   } else if ( o >= 2 ) { /* random int parameter 1 <= x <= parameter 2 */
      int l = luaL_checknumber( L, 1 );
      int h = luaL_checknumber( L, 2 );
      lua_pushnumber( L, l + ( h - l ) * RNGF() );
   } else
      NLUA_INVALID_PARAMETER( L, 1 );
 
   return 1; /* unless it's returned 0 already it'll always return a parameter
              */
}

static int rndL_angle( lua_State *L )
{
   lua_pushnumber( L, RNGF() * 2. * M_PI );
   return 1;
}

static int rndL_permutation( lua_State *L )
{
   int *values;
   int  max;
   int  new_table;
 
   if ( lua_isnumber( L, 1 ) ) {
      max       = lua_tointeger( L, 1 );
      new_table = 1;
   } else if ( lua_istable( L, 1 ) ) {
      max       = (int)lua_objlen( L, 1 );
      new_table = 0;
   } else
      NLUA_INVALID_PARAMETER( L, 1 );
 
   /* Create the list. */
   values = malloc( sizeof( int ) * max );
   for ( int i = 0; i < max; i++ )
      values[i] = i;
 
   /* Fisher-Yates shuffling algorithm */
   for ( int i = max - 1; i >= 0; --i ) {
      /* Generate a random number in the range [0, max-1] */
      int j = randint() % ( i + 1 );
 
      /* Swap the last element with an element at a random index. */
      int temp  = values[i];
      values[i] = values[j];
      values[j] = temp;
   }
 
   /* Now either return a new table or permute the given table. */
   lua_newtable( L );
   for ( int i = 0; i < max; i++ ) {
      lua_pushnumber( L, values[i] + 1 );
      if ( !new_table )
         lua_gettable( L, 1 );
      lua_rawseti( L, -2, i + 1 );
   }
 
   free( values );
   return 1;
}