Ds\Vector::reduce

(PECL ds >= 1.0.0)

Ds\Vector::reduce — Reduces the vector to a single value using a callback function.

说明

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

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

参数

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.

返回值

The return value of the final callback.

范例

Example #1 Ds\Vector::reduce() with initial value example

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

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

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

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

以上例程的输出类似于：

int(30)

Example #2 Ds\Vector::reduce() without an initial value example

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

var_dump($vector->reduce(function($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
?>

以上例程的输出类似于：

int(21)