Ds\Map::reduce
(PECL ds >= 1.0.0)
Ds\Map::reduce — Reduces the map to a single value using a callback function
說明
Reduces the map to a single value using a callback function.
參數
-
callback -
-
carry -
The return value of the previous callback, or
initialif 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.
返回值
The return value of the final callback.
範例
示例 #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
?>
以上例程的輸出類似於：
int(30)
示例 #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
?>
以上例程的輸出類似於：
int(21)