(PECL ds >= 1.0.0)
Ds\Deque::map — Returns the result of applying a callback to each value.
Returns the result of applying a callback function to
each value in the deque.
callback
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.
Note:
The values of the current instance won't be affected.
Example #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);
?>
以上例程的输出类似于：
Ds\Deque Object
(
[0] => 2
[1] => 4
[2] => 6
)
Ds\Deque Object
(
[0] => 1
[1] => 2
[2] => 3
)