Animating sprites

if (_bullet.AnimSpeed > 0)
{
    var _spr_frames = sprite_get_number(_bullet.Sprite); //Number of frames in the current Bullet Sprite.
    var _spr_animSpeed = sprite_get_speed(_bullet.Sprite) * (_bullet.AnimSpeed);
    var _spr_gameframe = spritespeed_framespergameframe;
    var _spr_conditional_1 = (sprite_get_speed_type(_bullet.Sprite) == _spr_gameframe);
    var _spr_conditional_2 = _spr_animSpeed / game_get_speed(gamespeed_fps);
    var _spr_spriteIndex = (_spr_conditional_1 ? _spr_animSpeed : _spr_conditional_2);

    _bullet.Sprite_Index += (_spr_spriteIndex mod _spr_frames);
}