Ds\Map::reduce

(PECL ds >= 1.0.0)

Ds\Map::reduceReduces the map to a single value using a callback function

説明

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

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

パラメータ

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.

戻り値

The return value of the final callback.

例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
?>

上の例の出力は、 たとえば以下のようになります。

int(30)

例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
?>

上の例の出力は、 たとえば以下のようになります。

int(21)
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