$command->execute();
$this->current += 1;
}
}
}
public function Undo(int $levels)
{
echo "Undo {$levels} levels\n";
for ($i = 0; $i < $levels; $i++) {
if ($this->current > 0) {
$this->current -= 1;
$command = $this->commands[$this->current];
$command->unExecute();
}
}
}
public function compute(string $oper, int $operand)
{
$command = new CalculatorCommand($this->calculator, $oper, $operand);
$command->execute();
$this->commands[] = $command;
$this->current = $this->current + 1;
}
}
$user = new User();
$user->compute('+', 100);
$user->compute('-', 50);
$user->compute('*', 10);
$user->compute('/', 2);
$user->undo(4);
$user->redo(3);
