在perl中合并哈希

Question

我想合并两个哈希。好吧，我能合并，但输出是不是我希望它的方式：

这里是我的代码：

my %friend_list = (
    Raj  => "Good friend", 
    Rohit  => "new Friend", 
    Sumit  => "Best Friend", 
    Rohini => "Fiend", 
    Allahabad => "UttarPradesh", 
); 

my %city = (
    Bangalore => "Karnataka", 
    Indore => "MadhyaPradesh", 
    Pune  => "Maharashtra", 
    Allahabad => "UP", 
); 

my %friends_place =(); 
my ($k, $v); 
foreach my $ref (\%friend_list, \%city) { 

    while (($k,$v) = each (%$ref)) { 

     if (exists $ref{$k}) { 

      print"Warning: Key is all ready there\n"; 
      next; 
     } 
     $friends_place{$k} = $v; 
    } 
} 

while (($k,$v) = each (%friends_place)) { 

    print "$k = $v \n"; 
} 

从这O/P是

Raj=Good friend 
Indore=MadhyaPradesh 
Rohit=new Fiend 
Bangalore=Karnataka 
Allahabad=UttarPradesh 
Sumit=Best Friend 
Pune=Maharashtra 
Rohini =Fiend 

但我想打印％FRIEND_LIST其次％城市第一。 我试图做的另一件事是，如果有任何重复的键，那么它应该给我一个警告信息。但它没有给我任何消息。正如我们在这里可以看到的，我们有Allahabad在这两个哈希。

感谢

Answer 1

线if (exists $ref{$k}) {是错误的，你可以看到它，如果你把use strict; use warnings;在开始时的脚本。

此外，这种线应if (exists $friends_place{$k}) {以产生大约重复键的消息。

Answer 2

与尝试：

my %firend_list = (
    Raj  => "Good friend", 
    Rohit  => "new Fiend", 
    Sumit  => "Best Friend", 
    Rohini => "Fiend", 
    Allahabad => "UttarPradesh", 
); 

my %city = (
    Bangalore => "Karnataka", 
    Indore => "MadhyaPradesh", 
    Pune  => "Maharashtra", 
    Allahabad => "UP", 
); 
#merging 
my %friends_place = (%friend_list, %city); 

而且，对于警告：

foreach my $friend(keys %friend_list){ 
print"Warning: Key is all ready there\n" if $friend ~~ [ keys %city ]; 

} 

Answer 3

由于哈希是无序的，你需要使用一个数组来存储排序：

my %friends_place = (%firend_list, %city); 
my @friends_place_keyorder = ((keys %firend_list), (keys %city)); 
if ((scalar keys %friends_place) != (scalar @friends_place_keyorder)) { 
    print 'duplicate key found'; 
} 
foreach (@friends_place_keyorder) { 
    print "$_ = $friends_place{$_}\n"; 
} 

编辑：我在python中的原始解决方案，在此留作历史用途：

由于哈希是无序的，所以您需要使用数组来存储排序。我不知道perl的，所以下面的代码是蟒蛇（应该是相当简单翻译成perl）：

friend_list = ... 
city = ... 
friends_place = dict(friend_list.items() + city.items()) 
friends_place_keyorder = friend_list.keys() + city.keys() 

# detect duplicate keys by checking their lengths 
# if there is duplicate then the hash would be smaller than the list 
if len(friends_place) != len(friends_place_keyorder): 
    print "duplicate key found" 

# iterate through the list of keys instead of the hashes directly 
for k in friends_place_keyorder: 
    print k, friends_place[k]