替换嵌套的foreach循环 [英] replace nested foreach loops

问题描述

我正在寻找一种使用功能性编程方法替换嵌套的foreach循环的方法.情况如下:

I'm looking for a way to replace nested foreach loops with a functional programming approach. Here is the situation:

$mode[1] = [1, 2, 5, 6];
$mode[0] = [3, 4, 7, 8];

目前我的代码是这样:

foreach ($mode as $key=>$value):
  foreach ($value as $v):
    $modes[$v] = $key;
  endforeach;
endforeach;

echo '<pre>' . print_r($modes, 1) . '</pre>';

生成所需的输出，如下所示:

which generates the desired output which looks like this:

有人知道如何用功能性编程替代方案替换foreach代码块吗?

Does anyone know how the foreach code block can be replaced with a functional programming alternative?

推荐答案

我认为 array_walk()与Union Operator合作，而 array_fill_keys()似乎是个不错的选择为此任务:

I think array_walk() partnered with a Union Operator and array_fill_keys() seems like a clean choice for this task:

代码:( 演示)

$mode[1]=[1, 2, 5, 6];
$mode[0]=[3, 4, 7, 8];

$result=[]; // declare empty array so that union operator works
array_walk($mode,function($a,$k)use(&$result){$result+=array_fill_keys($a,$k);});
var_export($result);

输出:

array (
  1 => 1,
  2 => 1,
  5 => 1,
  6 => 1,
  3 => 0,
  4 => 0,
  7 => 0,
  8 => 0,
)

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