Perl: concise way to map one array onto antother in perl hash

Suppose I have two arrays. Suppose further elements in one of this array logically map onto elements of the other.

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1. my @ar1 = (...);  
2. my @ar2 = (...);  

my @ar1 = (...);
my @ar2 = (...);

Easy way to map ar1 (keys) onto ar2 in perl is:

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1. my %hash;  
2. @hash{@ar1} = (@ar2) x @ar1;  

my %hash;
@hash{@ar1} = (@ar2) x @ar1;

Important assumption: the order in this two arrays matters. In other words first element of ar1 maps to first element of ar2, ..., n-th element of first array ar1 maps onto n-th element of ar2 and there exactly n elements in both arrays.


Examples

It is OK to have unique keys, obviously for the hash to preserve correct mapping (include use Data::Dumper in your code):

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1. sub unique_mapping  
2. {  
3.  my @ar1 = ('a', 'b', 'c', 'd', 'e');  
4.  my @ar2 = ('1', '2', '3', '4', '5');  
5.    
6.  print Dumper(\@ar1);  
7.  print Dumper(\@ar2);  
8.    
9.  my %hash;  
10.  @hash{@ar1} = (@ar2) x @ar1;  
11.    
12.    
13.  print Dumper(\%hash);  
14.    
15. }  

sub unique_mapping
{
 my @ar1 = ('a', 'b', 'c', 'd', 'e');
 my @ar2 = ('1', '2', '3', '4', '5');
 
 print Dumper(\@ar1);
 print Dumper(\@ar2);
 
 my %hash;
 @hash{@ar1} = (@ar2) x @ar1;
 
 
 print Dumper(\%hash);
 
}

Result:

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1. $VAR1 = [  
2.           'a',  
3.           'b',  
4.           'c',  
5.           'd',  
6.           'e'  
7.         ];  
8. $VAR1 = [  
9.           '1',  
10.           '2',  
11.           '3',  
12.           '4',  
13.           '5'  
14.         ];  
15. $VAR1 = {  
16.           'e' => '5',  
17.           'c' => '3',  
18.           'a' => '1',  
19.           'b' => '2',  
20.           'd' => '4'  
21.         };  

$VAR1 = [
          'a',
          'b',
          'c',
          'd',
          'e'
        ];
$VAR1 = [
          '1',
          '2',
          '3',
          '4',
          '5'
        ];
$VAR1 = {
          'e' => '5',
          'c' => '3',
          'a' => '1',
          'b' => '2',
          'd' => '4'
        };

The mapping is not what you might want to have in the case when keys are not unique:

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1. sub keys_non_unique_mapping  
2. {  
3.  my @ar1 = ('a', 'b', 'b', 'd', 'e');  
4.  my @ar2 = ('1', '2', '3', '4', '5');  
5.    
6.  print Dumper(\@ar1);  
7.  print Dumper(\@ar2);  
8.    
9.  my %hash;  
10.  @hash{@ar1} = (@ar2) x @ar1;  
11.    
12.    
13.  print Dumper(\%hash);  
14.    
15. }  

sub keys_non_unique_mapping
{
 my @ar1 = ('a', 'b', 'b', 'd', 'e');
 my @ar2 = ('1', '2', '3', '4', '5');
 
 print Dumper(\@ar1);
 print Dumper(\@ar2);
 
 my %hash;
 @hash{@ar1} = (@ar2) x @ar1;
 
 
 print Dumper(\%hash);
 
}

Result:

view plainprint?

1. $VAR1 = [  
2.           'a',  
3.           'b',  
4.           'b',  
5.           'd',  
6.           'e'  
7.         ];  
8. $VAR1 = [  
9.           '1',  
10.           '2',  
11.           '3',  
12.           '4',  
13.           '5'  
14.         ];  
15. $VAR1 = {  
16.           'e' => '5',  
17.           'a' => '1',  
18.           'b' => '3',  
19.           'd' => '4'  
20.         };  

$VAR1 = [
          'a',
          'b',
          'b',
          'd',
          'e'
        ];
$VAR1 = [
          '1',
          '2',
          '3',
          '4',
          '5'
        ];
$VAR1 = {
          'e' => '5',
          'a' => '1',
          'b' => '3',
          'd' => '4'
        };