如何减去一个数组的数组？ [英] How to subtract an array from an array?

问题描述

当我尝试以下方法

#!/usr/bin/perl

use strict;
use warnings;
use Data::Dumper;

my @bl = qw(red green blue);
my @a = qw(green yellow purple blue pink);

print Dumper [grep {not @bl} @a];

我得到一个空数组。我本来期望 @bl 从 @a 中减去，所以产量为黄色粉紫色。

I get an empty array. I would have expected that @bl was subtracted from @a, so the output was yellow purple pink.

什么是错在这里？

推荐答案

您需要打开 @bl 成散列执行差集：

You need to turn @bl into a hash to perform the set difference:

my %in_bl = map {$_ => 1} @bl;
my @diff  = grep {not $in_bl{$_}} @a;

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