(PECL ds >= 1.0.0)
Ds\Map::reduce — Reduces the map to a single value using a callback function
Reduces the map to a single value using a callback function.
callbackcarry
The return value of the previous callback, or initial if
it's the first iteration.
keyThe key of the current iteration.
valueThe value of the current iteration.
initial
The initial value of the carry value. Can be null.
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)