Question

我需要在Perl中创建依赖哈希。 program1取决于program2 program4 program10 program5 program7 program6等。数据是随机生成的，例如：

#!/usr/bin/env perl

use strict;
use warnings;

use Data::Dumper;
use English qw( -no_match_vars );

my $dependsOrder = {};
while (my $line = <DATA>) {
    chomp $line;
    my ( $component, $depends ) = split /:/, $line;
    if ( exists $dependsOrder->{$component} and $dependsOrder->{$component} == 1 ) {
        $dependsOrder->{$component} = {};
    }
    if ( $depends ) {
        $depends =~ s/^\s+|\s+$// if $depends;
        my @depends = split /\s+/, $depends;
        for my $dependency ( @depends ) {
            if ( not exists $dependsOrder->{$dependency} ) {
                # default value
                $dependsOrder->{$dependency} = 1;
            }
            $dependsOrder->{$component}->{$dependency} = $dependsOrder->{$dependency};
        }
    }
    else {
        $dependsOrder->{$component} = 1;
    }
}
print Dumper $dependsOrder->{'program1'};
#print Dumper $dependsOrder->{'program6'};

__DATA__
program1: program2 program4 program10 program5 program7 program6
program2: program7 program5 program9 program8 program10 program3 program6 program1
program3: program2 program9 program8
program4: program5 program8 program10 program1 program2 program2 program9
program5: program3 program6 program4 program7
program6: program5 program8 program7
program7: program1 program2 program9 program10
program8: program1 program9 program6 program10 program3 program2 
program9: 
program10: program6 program9

此代码不起作用：

$VAR1 = {
          'program7' => 1,
          'program10' => 1,
          'program6' => 1,
          'program2' => 1,
          'program4' => 1,
          'program5' => 1
        };

但如果我改变第22行：

$dependsOrder->{$dependency} = 1;

使用：

$dependsOrder->{$dependency} = {};

它工作正常，但我没有默认值：

$VAR1 = {
          'program7' => {
                          'program2' => {
                                          'program8' => {
                                                          'program9' => {},
                                                          'program6' => {

我的默认值推理有什么问题？

Answer 1

将数据减少到以下内容可以更有效地检查问题：

program1: program2
program2: program7

在第一种情况下，你所做的归结为

$d->{p2} = 1;
$d->{p1}{p2} = $d->{p2};     # $d->{p1}{p2} = 1;
$d->{p2} = {};
$d->{p7} = 1;
$d->{p2}{p7} = $d->{p7};     # $d->{p2}{p7} = 1;

$d->{p1}{p2}包含1，$d->{p2}包含对在最后一行修改的哈希的引用。

在第二种情况下，你所做的归结为

$d->{p2} = {};
$d->{p1}{p2} = $d->{p2};
$d->{p7} = {};
$d->{p2}{p7} = $d->{p7};

$d->{p1}{p2}和$d->{p2}包含对同一哈希的引用，该哈希在最后一行中进行了修改。

您的代码可能写成如下：

my %dependency_tree;
while (<DATA>) {
    chomp;
    my ( $component, $depends ) = split /:/;
    $dependency_tree{$component} ||= {};
    for my $dependency (split ' ', $depends) {
        $dependency_tree{$component}{$dependency} =
            $dependency_tree{$dependency} ||= {};
    }
}

Perl嵌套程序依赖的哈希值

1 个答案: