Ds\Map::reduce

(PECL ds >= 1.0.0)

Ds\Map::reduce — Reduces the map to a single value using a callback function

Beschreibung

public Ds\Map::reduce(callable $callback, mixed $initial = ?): mixed

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

Parameter-Liste

callback

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

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

initial

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

Rückgabewerte

The return value of the final callback.

Beispiele

Beispiel #1 Ds\Map::reduce() with initial value example

<?php
$map = new \Ds\Map(["a" => 1, "b" => 2, "c" => 3]);

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

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

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

Das oben gezeigte Beispiel erzeugt eine ähnliche Ausgabe wie:

int(30)

Beispiel #2 Ds\Map::reduce() without an initial value example

<?php
$map = new \Ds\Map(["a" => 1, "b" => 2, "c" => 3]);

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

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

Das oben gezeigte Beispiel erzeugt eine ähnliche Ausgabe wie:

int(21)

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