/*
** This function uses 'double' (instead of 'lua_Number') to ensure that
** all bits from 'l_rand' can be represented, and that 'RANDMAX + 1.0'
** will keep full precision (ensuring that 'r' is always less than 1.0.)
*/
static int math_random(lua_State *L) {
lua_Integer low, up;
double r = (double)l_rand() * (1.0 / ((double)L_RANDMAX + 1.0));
switch (lua_gettop(L)) { /* check number of arguments */
case 0: { /* no arguments */
lua_pushnumber(L, (lua_Number)r); /* Number between 0 and 1 */
return 1;
}
case 1: { /* only upper limit */
low = 1;
up = luaL_checkinteger(L, 1);
break;
}
case 2: { /* lower and upper limits */
low = luaL_checkinteger(L, 1);
up = luaL_checkinteger(L, 2);
break;
}
default: return luaL_error(L, "wrong number of arguments");
}
/* random integer in the interval [low, up] */
luaL_argcheck(L, low <= up, 1, "interval is empty");
luaL_argcheck(L, low >= 0 || up <= LUA_MAXINTEGER + low, 1,
"interval too large");
r *= (double)(up - low) + 1.0;
lua_pushinteger(L, (lua_Integer)r + low);
return 1;
}
static int tshuffle (lua_State *L) {
lua_Integer begin, end;
checktab(L, 1, TAB_RW);
begin = luaL_optinteger(L, 2, 1);
end = luaL_opt(L, luaL_checkinteger, 3, check_n(L, 1));
while (end >= begin) {
double f = l_rand() * (1.0/(L_RANDMAX+1.0));
lua_Integer j = begin + (lua_Integer)(f * (end-begin+1));
lua_geti(L, 1, end);
lua_geti(L, 1, j);
lua_seti(L, 1, end);
lua_seti(L, 1, j);
--end;
}
return 0;
}
static int math_randomseed (lua_State *L) {
l_srand((unsigned int)(lua_Integer)luaL_checknumber(L, 1));
(void)l_rand(); /* discard first value to avoid undesirable correlations */
return 0;
}
