如何获取取消引用的匿名数组的第 n 个元素? [英] How can I get the nth element of a dereferenced anonymous array?

问题描述

use strict;

my $anon = [1,3,5,7,9];
my $aref  = [\$anon];

print "3rd element: "  . $ { $aref } [2] . "\n";

我想通过 $aref 变量获取匿名数组 $anon 的第 n 个元素.在代码中，我想通过使索引为 2 来获取 $anon 的第三个元素，但它什么也没返回.如果我写 $ { $aref } [0] 然后它返回类似 REF(0x7fd459027ac0)

I'd like to get the nth element of the anonymous array $anon over the $aref variable. In the code I wanted to get the 3rd element of $anon by making the index 2 but it returned nothing. If I write $ { $aref } [0] then it returns something like REF(0x7fd459027ac0)

如何获得第 n 个，例如 $anon 的第 3 个元素?

How can I get the nth, for example the 3rd element of $anon ?

理由:

my @area = (
    qw[1 3 5 7 9],
    qw[2 4 6 8 0],
    qw[a e i u o],
    qw[b c d f g]
    );

foreach my $row (@area) {
    foreach my $cell (@$row)
    {
    # do some processing on the element
    print $cell . " ";
    }
    print "\n";
}

推荐答案

如何获取解除引用的匿名数组的第 n 个元素?

How can I get the nth element of a dereferenced anonymous array?

您有太多引用运算符.您已经构建了一个三层深的嵌套结构，难怪您在导航时遇到问题

You have too many reference to operators. You have built a nested structure three levels deep and it's no wonder you're having trouble navigating it

问题是你的$anon 已经是一个匿名数组的引用.方括号 [...] 构造一个匿名数组并返回对它的引用

The problem is that your $anon is already a reference to an anonymous array. Square brackets [...] construct an anonymous array and return a reference to it

然后你有

my $aref  = [\$anon]

它创建另一个对具有一个元素的数组的引用:对 scalar $anon 的引用.

which creates another reference to an array with one element: a reference to the scalar $anon.

所以你已经构建了这个

$anon = [1, 3, 5, 7, 9]

$aref = [ \ [1, 3, 5, 7, 9] ]

所以

${$aref}[0]          is \ [1, 3, 5, 7, 9]
${${$aref}[0]}       is [1, 3, 5, 7, 9]
${${${$aref}[0]}}[2] is 5

但是为什么要使用对数组的引用，尤其是对标量的引用?最好从普通数组开始，写

But why are you working with references to arrays at all, and especially references to scalars? It would be best to begin with an ordinary array, and write

my @array = ( 1, 3, 5, 7, 9 );
my $aref = \@array;

print $aref->[2];

输出

5

这篇关于如何获取取消引用的匿名数组的第 n 个元素?的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！