http://qs321.pair.com?node_id=780180


in reply to Re^3: Array to hash converstion
in thread Array to hash converstion

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

my @value_pairs = qw (one abc two xyz);
my %hash = @value_pairs;

foreach my $key (keys %hash)
{
   print "key $key is $hash{$key}\n";
}
__END__
prints:
key one is abc
key two is xyz
key one is def

[download]
If two keys are same then, output is 
key one is abc
key two is xyz

[download]
so for the key one value is def is not printed here. The expected output is 
key one is abc
key two is xyz
key one is def

[download]
Please tell me how can I get the output like this

Replies are listed 'Best First'.
Re^5: Array to hash converstion
by dsheroh (Monsignor) on Jul 15, 2009 at 09:41 UTC
    The issue you've run into here is that each hash key can only be associated with a single value, so the second assignment to $hash{one} overwrites its previous value. Or, as spazm put it in the comment you were replying to,
    My solutions below assume that you have unique key values, or are un-interested in collisions. In the case of a collision, the last reference to the key wins.
    However, the single value held by the hash doesn't have to be a simple scalar. If you use an array reference there (giving you a "hash of arrays" or "HoA"), then the code will be a little more complex, but you'll be able to store as many values as you like with each key: 
    #!/usr/bin/perl

use strict;
use warnings;

my @value_pairs = qw( one abc two xyz one def );
my %hash;

while (@value_pairs) {
  my $key = shift @value_pairs;
  my $value = shift @value_pairs;
  push @{$hash{$key}}, $value;
}

for my $key (keys %hash) {
  print "key $key has values: ", join(', ', @{$hash{$key}}), "\n";
}
__END__
key one has values: abc, def
key two has values: xyz

    [download]
[reply]
[d/l]
[select]
       
$correction = $data_pair->{value} if($data_pair->{key} eq 'correct');

      [download]
      how to store the value in $correction only if the $data_pair->{value} is not empty.
[reply]
[d/l]
        check to see if it is empty (whatever that means :D) 
        $correction = $data_pair->{value}
    if exists $data_pair->{value} and    # could be undef
      defined $data_pair->{value} and    # at least ""
      length $data_pair->{value}  and    # has length
      $data_pair->{value}         and    #  has true value
      $data_pair->{key} eq 'correct';

        [download]
[reply]
[d/l]

In Section Seekers of Perl Wisdom