Deque
PHP Manual

Ds\Deque::reduce

Reduces the deque to a single value using a callback function.

Description

public mixed Ds\Deque::reduce ( callable $callback [, mixed $initial ] )

Reduces the deque to a single value using a callback function.

Parameters

callback
mixed callback ( mixed $carry , mixed $value )
carry

The return value of the previous callback, or initial if it's the first iteration.

value

The value of the current iteration.

initial

The initial value of the carry value. Can be NULL.

Return Values

The return value of the final callback.

Examples

Example #1 Ds\Deque::reduce with initial value example

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

$callback = function($carry, $value) {
    return $carry * $value;
};

var_dump($deque->reduce($callback, 5));

// Iterations:
//
// $carry = $initial = 5
//
// $carry = $carry * 1 =  5
// $carry = $carry * 2 = 10
// $carry = $carry * 3 = 30
?>

The above example will output something similar to:

int(30)

Example #2 Ds\Deque::reduce without an initial value example

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

var_dump($deque->reduce(function($carry, $value) {
    return $carry + $value + 5;
}));

// Iterations:
//
// $carry = $initial = null
//
// $carry = $carry + 1 + 5 =  6
// $carry = $carry + 2 + 5 = 13
// $carry = $carry + 3 + 5 = 21
?>

The above example will output something similar to:

int(21)