Perl 复杂数据结构

01. 举个二维哈希的例子

#!/usr/bin/perl

use warnings;
use strict;
use Data::Dumper qw(Dumper);

#creating 2D hash
my %company = ('Sales' =>    { 
                                'Brown' => 'Manager', 
                                'Smith' => 'Salesman', 
                                'Albert' => 'Salesman',  
                            },  
            'Marketing' =>  { 
                                'Penfold' => 'Designer', 
                                'Evans' => 'Tea-person', 
                                'Jurgens' => 'Manager',  
                            }, 
            'Production' => { 
                                'Cotton' => 'Paste-up', 
                                'Ridgeway' => 'Manager', 
                                'Web' => 'Developer',  
                            }, 
            );  
# print the list
print Dumper \%company;

OUTPUT

$VAR1 = {
          'Marketing' => {
                           'Evans' => 'Tea-person',
                           'Jurgens' => 'Manager',
                           'Penfold' => 'Designer'
                         },
          'Sales' => {
                       'Smith' => 'Salesman',
                       'Albert' => 'Salesman',
                       'Brown' => 'Manager'
                     },
          'Production' => {
                            'Ridgeway' => 'Manager',
                            'Web' => 'Developer',
                            'Cotton' => 'Paste-up'
                          }
        };

• Dumper函数可以将复杂结构展示出来

02. 向哈希添加元素

$company{'new_key'} = {
    'sub_key1' => value1,
    'sub_key2' => value2,
    'sub_key3' => value3
}

03.读取特定值

print $company{"Production"}{"Web"}
# will output "Developer"

04.设置特定键的值

$company{$Production}->{"Web"} =  Senior Developer
# changes Web to Senior Developer

05.遍历多维哈希

若要遍历多维散列或遍历散列中的每个值，只需遍历外部散列的键，然后遍历内部散列的键。对于n维哈希，需要n个嵌套循环或嵌入循环遍历完整的哈希。for和while循环都可以用来循环到散列。

for $key (keys %hash) 
{ 
    print "$key: \n"; 
    for $ele (keys %{$hash{$key}}) 
    { 
        print " $ele: " . $hash{$key}->{$ele} . "\n"; 
    } 
} 

对于大型多维散列，使用“each”同时检索键和值可能会稍微快一些。

while (($key, $ele) = each %hash) 
{ 
    print "$key: \n"; 
    while (($ele, $sub_ele) = each %$ele) 
    { 
        print " $ele = $sub_ele "; 
    } 
    print "\n"; 
} 

下面的示例演示如何使用for和while循环遍历多维哈希：

use strict;
use warnings;
use Data::Dumper

my %company = ('Sales' =>    { 
                                'Brown' => 'Manager', 
                                'Smith' => 'Salesman', 
                                'Albert' => 'Salesman',  
                            },  
            'Marketing' =>  { 
                                'Penfold' => 'Designer', 
                                'Evans' => 'Tea-person', 
                                'Jurgens' => 'Manager',  
                            }, 
            'Production' => { 
                                'Cotton' => 'Paste-up', 
                                'Ridgeway' => 'Manager', 
                                'Web' => 'Developer',  
                            }, 
            );  
print "Traversing hash using For loop: "."\n"; 
print "\n"; 
  
# traversing hash using for loop 
for my $key (keys %company) {
    print "$key\n";
    for my $ele (keys %{$company{$key}}){
        print " $ele: " . $company{$key}->{$ele} . "\n";
 }
} 

print "\nTraversing hash using while" .  
      "loop using each keyword: " . "\n"; 
print "\n"; 
  
# traversing hash using each keyword 
# and while loop 
while ((my $key, my $ele) = each %company) { 
    print "$key: \n"; 
    while ((my $ele, my $sub_ele) = each %$ele)  { 
        print " $ele = $sub_ele "; 
    } 
        print "\n"; 
} 

output

Traversing hash by For loop.

Marketing: 
 Evans: Tea-person
 Jurgens: Manager
 Penfold: Designer
Sales: 
 Brown: Manager
 Albert: Salesman
 Smith: Salesman
Production: 
 Cotton: Paste-up
 Web: Developer
 Ridgeway: Manager

Traversing hash using while loop with each keyword.

Marketing: 
 Evans=Tea-person  Jurgens=Manager  Penfold=Designer 
Sales: 
 Brown=Manager  Albert=Salesman  Smith=Salesman 
Production: 
 Cotton=Paste-up  Web=Developer  Ridgeway=Manager 

06.检测多维哈希的键值

很多时候，当使用perl哈希时，我们需要知道哈希中是否已经存在某个键。给定一个散列，就可以通过使用exists关键字来检查特定密钥的存在。在上面示例中使用的像%Company这样的多维哈希中，必须一直使用关键字exists，直到检查到是否存在的键的深度级别为止。

if (exists($hash{key})) {
if (exists($hash{key}{sub_key})) {
….
}
}

下面是一个演示Perl存在散列函数的简单示例。在这个Perl脚本中，我们首先创建一个简单的Perl哈希，然后使用exists函数查看哈希中是否存在名为‘Albert’的哈希键。

# !/usr/bin/perl  
use strict; 
use warnings; 
my %company = ('Sales' => { 
                                'Brown' => 'Manager', 
                                'Smith' => 'Salesman', 
                                'Albert' => 'Salesman', 
                            }, 
            'Marketing' => { 
                                'Penfold' => 'Designer', 
                                'Evans' => 'Tea-person', 
                                'Jurgens' => 'Manager', 
                            }, 
            'Production' => { 
                                'Cotton' => 'Paste-up', 
                                'Ridgeway' => 'Manager', 
                                'Web' => 'Developer', 
                            }, 
            ); 

# Check for key existence 
if (exists $company{"Sales"}) { 
    print "Sales department exists.\n"; 
    if (exists $company{"Sales"}{"Albert"}) { 
        print "Albert is " . $company{"Sales"}{"Albert"} . 
            " of Sales department . \n"; 
    } 
    else { 
        print "Albert is not a member of Sales department.\n"; 
    } 
} 
else { 
    print "Sales department do not exists.\n"; 
} 

# output

Sales department exists.
Albert is Salesman of Sales department.

07.从文件读取存入多维哈希

flintstones: husband=fred pal=barney wife=wilma pet=dino

while (<>){
    next unless s/^(.*?):\s*//;
    $who = $1;
    for $field (split) {
        ($key, $value) = split /=/, $field;
        $HoH{$who}{$key} = $value
  }
}

whike (<>) {
    next unless s/^(.*?):\s*//;
    $who = $1;
    $rec = {};
    $HoH{$who} = $rec;
    for $field (split) {
         ($key, $value) = split /=/, $field;
          $rec -> {$key} = $value;
 }

}