在Perl中，有一个内置的方式来比较两个数组是否相等？ [英] In Perl, is there a built in way to compare two arrays for equality?

问题描述

我有一个字符串的两个数组，我想比较平等：

I have two arrays of strings that I would like to compare for equality:

my @array1 = ("part1", "part2", "part3", "part4");
my @array2 = ("part1", "PART2", "part3", "part4");

有一个内置的方式比较数组像有标量？
我想：

Is there a built-in way to compare arrays like there is for scalars? I tried:

if (@array1 == @array2) {...}

，但它只是评价在标量上下文每个阵列，并且因此相比每个阵列的长度。

but it just evaluated each array in scalar context, and so compared the length of each array.

我可以推出自己的函数来做到这一点，但似乎这样的低级操作，应该有一个内置的方式做到这一点。有没有？

I can roll my own function to do it, but it seems like such a low-level operation that there should be a built-in way to do it. Is there?

编辑：可悲的是，我没有5.10+或可选组件的访问

sadly, I don't have access to 5.10+ or optional components.

推荐答案

有是新的智能匹配运营商：

#!/usr/bin/perl

use 5.010;
use strict;
use warnings;

my @x = (1, 2, 3);
my @y = qw(1 2 3);

say "[@x] and [@y] match" if @x ~~ @y;

::比较：

在内部比较器通过加入把两个数组转换为字符串，并使用比较字符串 EQ 。

Internally the comparator compares the two arrays by using join to turn both arrays into strings and comparing the strings using eq.

我想这是一个有效的方法，但只要我们使用字符串比较，我宁愿使用这样的：

I guess that is a valid method, but so long as we are using string comparisons, I would much rather use something like:

#!/usr/bin/perl

use strict;
use warnings;

use List::AllUtils qw( each_arrayref );

my @x = qw(1 2 3);
my @y = (1, 2, 3);

print "[@x] and [@y] match\n" if elementwise_eq( \(@x, @y) );

sub elementwise_eq {
    my ($xref, $yref) = @_;
    return unless  @$xref == @$yref;

    my $it = each_arrayref($xref, $yref);
    while ( my ($x, $y) = $it->() ) {
        return unless $x eq $y;
    }
    return 1;
}

如果你是比较数组很大，加入他们会做了很多工作，并消耗大量的内存比一个只是每个元素的一个比较。

If the arrays you are comparing are large, joining them is going to do a lot of work and consume a lot of memory than just comparing each element one by one.

更新：当然，人们应该测试这样的语句。简单的标准：

Update: Of course, one should test such statements. Simple benchmarks:

#!/usr/bin/perl

use strict;
use warnings;

use Array::Compare;
use Benchmark qw( cmpthese );
use List::AllUtils qw( each_arrayref );

my @x = 1 .. 1_000;
my @y = map { "$_" } 1 .. 1_000;

my $comp = Array::Compare->new;

cmpthese -5, {
    iterator => sub { my $r = elementwise_eq(\(@x, @y)) },
    array_comp => sub { my $r = $comp->compare(\(@x, @y)) },
};

这是最坏的情况，其中 elementwise_eq 要经过的每一个元素在两个数组1_000倍，它表明：

This is the worst case scenario where elementwise_eq has to go through each and every element in both arrays 1_000 times and it shows:

             Rate   iterator array_comp
iterator    246/s         --       -75%
array_comp 1002/s       308%         --

在另一方面，最好的情况是：

On the other hand, the best case scenario is:

my @x = map { rand } 1 .. 1_000;
my @y = map { rand } 1 .. 1_000;

              Rate array_comp   iterator
array_comp   919/s         --       -98%
iterator   52600/s      5622%         --

迭代器性能下降得很快，但是：

iterator performance drops quite quickly, however:

my @x = 1 .. 20, map { rand } 1 .. 1_000;
my @y = 1 .. 20, map { rand } 1 .. 1_000;

              Rate   iterator array_comp
iterator   10014/s         --       -23%
array_comp 13071/s        31%         --

我没看内存利用率。

I did not look at memory utilization.

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