PHP Ds Map reduce()用法及代码示例

Ds\Map::reduce() 函数可以通过使用回调函数将映射减少到单个值。

用法

public mixed Ds\Map::reduce( callable $callback [, mixed $initial ] )

Ds\Map::reduce() 函数可以返回最终回调的值。

例子1

<?php  
   $map = new \Ds\Map(["a" => 1, "b" => 2, "c" => 3]);  
   
   echo("The map elements:\n");  
   print_r($map);  
   
   echo("\n An element after performing operation:\n");  
  
   var_dump($map->reduce(function($carry, $key, $element) {  
      return $carry + $element + 2;  
   }));  
?>

例子2

<?php  
   $map = new \Ds\Map(["a" => 10, "b" => 20, "c" => 30, "d" => 40]);  
   
   echo("The original map elements:\n");  
   print_r($map);  
   
   $func = function($carry, $key, $element) {  
      return $carry * $element;  
   };  
   echo("\n The map after reducing to single element:\n");  
   var_dump($map->reduce($func, 10));  
?>