PHP Manual: Returns the result of applying a callback to each value

abstract public Ds\Sequence Ds\Sequence::map(callable $callback)

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

callback

mixed callback(mixed $value)

A callable to apply to each value in the sequence.

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

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

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

Example #1 Ds\Sequence::map example

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

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

The above example will output something similar to:

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