Ds\Map::reduce

(PECL ds >= 1.0.0)

Ds\Map::reduceReduces 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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