perl - 查找多维数组大小

Question

用()有什么区别在 Perl 中与 []例如，当数组使用方括号时，如何找到数组的大小？

my @myarr = ( # Parenthesis
                [ "itemone", "itemoneb", "itemonec" ],
                [ "itemtwo", "itemtwob", "itemtwoc" ]
               );

my @myarr = [ # Square bracket
                [ "itemone", "itemoneb", "itemonec" ],
                [ "itemtwo", "itemtwob", "itemtwoc" ]
               ];

谢谢你的解释。我仍在努力理解这一点，目前这让我有点困惑。我仍然无法弄清楚如何在这里迭代我的数据:

#!/usr/bin/perl -w

use strict;
use FindBin qw($Bin);
use Cwd;
use Data::Dumper;

my @mynames = (
                [ "myname", "mydescription", "mydata"],
                [ "myname2", "mydescription2", "mydata2"],
                [ "myname3", "mydescription3", "mydata3"],
               );


go();

sub go {
    start(\@mynames);
}

sub start {
    my @input_name = shift;

    # This works
    #print @input_name->[0][0][0];
    #die;

    # This Shows
    #print Dumper(@input_name);
    #$VAR1 = [
    #          [
    #            'myname',
    #            'mydescription',
    #            'mydata'
    #          ],
    #          [
    #            'myname2',
    #            'mydescription2',
    #            'mydata2'
    #          ],
    #          [
    #            'myname3',
    #            'mydescription3',
    #            'mydata3'
    #          ]
    #        ];

    # How do I iterate?
    #for my $i (0..@$input_name) {
    #    my $name = "";
    #    my $description = "";
    #    my $data = "";
    #
    #}
}

Answer 1

这是错误的:

my @myarr = [
                [ "itemone", "itemoneb", "itemonec" ],
                [ "itemtwo", "itemtwob", "itemtwoc" ]
               ];

它应该是:

my $myarr = [
                [ "itemone", "itemoneb", "itemonec" ],
                [ "itemtwo", "itemtwob", "itemtwoc" ]
               ];

上面是“$myarr”。方括号将返回对标量列表的引用。因此需要使用“$”而不是“@”。
或者

my @myarr = (
                [ "itemone", "itemoneb", "itemonec" ],
                [ "itemtwo", "itemtwob", "itemtwoc" ]
               );

上面是“()”而不是“[]”。 “()”将返回列表，因此它需要“@”。
检查以下迭代 AoA 的代码。这样您就可以访问 AoA 的所有元素。以及单个元素:

#!/usr/bin/perl -w
use strict;

my @mynames = (
                [ "myname", "mydescription", "mydata"],
                [ "myname2", "mydescription2", "mydata2"],
                [ "myname3", "mydescription3", "mydata3"],
              );

### To access all the elements in above AoA
foreach my $a (@mynames)
{
    foreach my $b ( @{$a} )
    {
        print $b."\t";
    }
    print "\n";
}
print "====================================\n";

### To access individual elements:
print $mynames[1][2]."\n"; ### It prints mydata2

您可能想阅读 perlref学习和理解 Perl 引用和嵌套数据结构。