递减字母值 [英] Decrementing alphabetical values

问题描述

我试图弄清楚如何将数组中的一堆字母值向下移动一个步骤.例如，我的数组包含值("d"，"e"，"f"，"g"，"h")，而我想将其更改为("c"，"d"，"e"，"f" ， G").这是我正在使用的代码:

I'm trying to figure out how to shift a bunch of letter values in an array down one step. For example, my array contains values ("d", "e", "f", "g", "h") and I want to change this to ("c", "d", "e", "f", "g"). Here's the code I'm working with:

function move_up_left($x) {
    if($x['orientation'] == "down") {
        foreach($x[0] as &$value) {
            $value = --$value; 
        }
    } else {
        foreach($x[1] as &$value) {
            $value = --$value;
        }
    }

    return $x;
}

当我使用正值时，字母会发生变化；但是，负数似乎根本不起作用.

When I use positive values, the letters change; however the negative numbers do not seem to be working at all.

推荐答案

PHP为字符串重载了++； --并非如此.您可以使用 chr ， array_map :

PHP has overloaded ++ for strings; this isn't the case for --. You can do the same thing with much cleaner code with chr, ord, and array_map:

function decrementLetter($l) {
    return chr(ord($l) - 1);
}

function move_up_left($x) {
    if($x['orientation'] === 'down') $arr = &$x[0];
    else $arr = &$x[1];

    $arr = array_map('decrementLetter', $arr);

    return $x;
}

这是一个演示.请注意，您可能需要添加一种特殊情况来减小a-我我不确定您要如何处理.

Here's a demo. Note that you may need to add a special case for decrementing a - I'm not sure how you want to deal with that.

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