weird variable concatenation

newatperl has asked for the wisdom of the Perl Monks concerning the following question:

Some sorta of variable/array concat is happening here:

$one = "YAR033W";
$two = "YAR033W";
@source = ("ITOCORE");
@exper = ("n/a");
print " ($one)($two)(@source)(@exper) \n";
parsed_pair($one, $two, @source, @exper);
...

sub parsed_pair
{
my ($one, $two, @source, @exper) = @_;
print " ($one)($two)(@source)(@exper) \n";

....
}
[download]

The output I get is:

 (YAR033W)(YAR033W)(ITOCORE)(n/a) 
 (YAR033W)(YAR033W)(ITOCORE n/a)()
[download]

The two printouts should be exactly the same. I'm not even sure how to address this. Anyone have any idea why they're not?

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Re: weird variable concatenation by Chmrr (Vicar) on Mar 07, 2002 at 05:36 UTC
It's not a concatination problem, it's an array greediness problem. That is, saying: `my (@foo, @bar) = (1,2,3,4);` ..will leave @bar empty -- and rightfully so, as perl has no way of knowing which values were destined for which array. This is much the same problem that you're running into. See the answer at perlfaq.com for the canonical way to fix this. Update: Bah, I thought at first glance that perlfaq actually gave a snippet of working example code, but they don't. So here's one way to do it: `$one = "YAR033W"; $two = "YAR033W"; @source = ("ITOCORE"); @exper = ("n/a"); print " ($one)($two)(@source)(@exper) \n"; parsed_pair($one, $two, \@source, \@exper); # ... sub parsed_pair { my ($one, $two, $source_ref, $exper_ref) = @_; print " ($one)($two)(@$source_ref)(@$exper_ref) \n"; #.... }` [download] See the pass by reference section of perlsub, and/or perlreftut / perlref. perl -pe '"I lo`+$^X$\"$]!$/"=~m%(.)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'	[reply] [d/l] [select]

Replies are listed 'Best First'.

Re: weird variable concatenation
by Chmrr (Vicar) on Mar 07, 2002 at 05:36 UTC

It's not a concatination problem, it's an array greediness problem. That is, saying:

my (@foo, @bar) = (1,2,3,4);

..will leave @bar empty -- and rightfully so, as perl has no way of knowing which values were destined for which array. This is much the same problem that you're running into. See the answer at perlfaq.com for the canonical way to fix this.

Update: Bah, I thought at first glance that perlfaq actually gave a snippet of working example code, but they don't. So here's one way to do it:


$one = "YAR033W";
$two = "YAR033W";
@source = ("ITOCORE");
@exper = ("n/a");
print " ($one)($two)(@source)(@exper) \n";
parsed_pair($one, $two, \@source, \@exper);
# ...

sub parsed_pair {
  my ($one, $two, $source_ref, $exper_ref) = @_;
  print " ($one)($two)(@$source_ref)(@$exper_ref) \n";
  #....
}
[download]

See the pass by reference section of perlsub, and/or perlreftut / perlref.

perl -pe '"I lo*`+$^X$\"$]!$/"=~m%(.*)%s;$_=$1;y^`+*^e v^#$&V"+@( NO CARRIER'

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