In trying to cut my code to a minimum, I have come up against a stumbling point in replacing a perfunc:foreach loop with a perlfunc:map statement - This stumbling point revolves around the following code:

#!/usr/bin/perl -Tw

use CGI;
use XML::Simple;
use strict;

my $xs = XML::Simple->new;
my $xml = eval { $xs->XMLin('../xml/users.xml') };
die $@ if ($@);

my $cgi = CGI->new;

my @foreach;
foreach (@{%{$xml}->{'user'}}) {
    push (@foreach, $_) if $_->{'username'} eq $cgi->param('username')
+;
};

my @map = map { $_ if $_->{'username'} eq $cgi->param('username'); } @
+{%{$xml}->{'user'}};

[download]

To my mind, the foreach and map segments of code are equivalent - Herein lies the problem I suspect. They are not.

If indeed, these pieces of code are equivalent, one could rightly expect the output arrays of each code segment to be the same for a given input. This is not occurring - Instead, the array output from the map code segment comprises of a large number of null values (one for each non-matching field) and the single result expected (and returned from the foreach code segment).

And so my question is ... What am I doing wrong here? Is there a way to have map return no value (compared with null value) into the output array if a given condition on the input scalar is not met?

 

Ooohhh, Rob no beer function well without!

In reply to foreach/map equivalency by rob_au

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