(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.
callback
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
.
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)