PHP マニュアル: Returns the result of applying a callback to each value

public Ds\Deque Ds\Deque::map(callable $callback)

Returns the result of applying a callback function to each value in the deque.

callback

mixed callback(mixed $value)

A callable to apply to each value in the deque.

The callable should return what the new value will be in the new deque.

The result of applying a callback to each value in the deque.

注意:
The values of the current instance won't be affected.

例1 Ds\Deque::map example

<?php
$deque = new \Ds\Deque([1, 2, 3]);

print_r($deque->map(function($value) { return $value * 2; }));
print_r($deque);
?>

上の例の出力は、たとえば以下のようになります。

Ds\Deque Object
(
    [0] => 2
    [1] => 4
    [2] => 6
)
Ds\Deque Object
(
    [0] => 1
    [1] => 2
    [2] => 3
)