GameBoy\Opcode::opcode157 PHP Method

    public static function opcode157(Core $core)
    {
        $dirtySum = $core->registerA - ($core->registersHL & 0xff) - ($core->FCarry ? 1 : 0);
        $core->FHalfCarry = ($core->registerA & 0xf) - ($core->registersHL & 0xf) - ($core->FCarry ? 1 : 0) < 0;
        $core->FCarry = $dirtySum < 0;
        $core->registerA = $core->unsbtub($dirtySum);
        $core->FZero = $core->registerA == 0;
        $core->FSubtract = true;
    }