Re: Force 'sub' return to be treated in list context?

You haven't shown us a test case which fails so I'm guessing, but if you write:

my $thing = UnPack (1, $stringpack);
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$thing will get a count instead of the "first" element of the returned array because UnPack is called in scalar context. Consider:

use strict;
use warnings;

my @single = (1);
my @many   = (1 .. 3);

for my $ref (\@single, \@many) {
    my $count    = listy(@$ref);
    my @elements = listy(@$ref);
    my ($firstElement) = listy(@$ref);

    print "Count $count, first: $firstElement, elements: @elements\n";
}


sub listy {
    return @_;
}
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Prints:

Count 1, first: 1, elements: 1
Count 3, first: 1, elements: 1 2 3
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If you write:

my ($thing) = UnPack (1, $stringpack);
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I suspect your problem will be resolved. It's not what you return, it's the context that is important and the () provides a list context.

True laziness is hard work

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Re^2: Force 'sub' return to be treated in list context? by flexvault (Monsignor) on Apr 04, 2012 at 11:46 UTC
GrandFather, I did show how to use the UnPack, but the following should demonstrate: `# Use: ## n - number of 64bit pack +ed numbers in string # my @Numbers = UnPack( n, $stringpack ); ## string input, array outp +ut my $pack = pack("N N", 0, 99 ); my $Numbers = UnPack( 1, $pack ); say $Numbers; ( $Numbers ) = UnPack( 1, $pack ); say $Numbers; my @Numbers = UnPack( 1, $pack ); say $Numbers[0]; ( @Numbers ) = UnPack( 1, $pack ); say $Numbers[0]; __END__ result: 1 99 99 99` [download] On running this code, I could not reproduce my original statement, so I can only assume that I typed "$Numbers" instead of "@Numbers" when I wrote the test cases for 'sub UnPack'. But if I had put parenthesis around the scalar, I still would have gotten what I wanted ( list context ). Thank you "Well done is better than well said." - Benjamin Franklin	[reply] [d/l]

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Re^2: Force 'sub' return to be treated in list context?
by flexvault (Monsignor) on Apr 04, 2012 at 11:46 UTC

GrandFather,

I did show how to use the UnPack, but the following should demonstrate:

# Use:                                     ## n - number of 64bit pack
+ed numbers in string
# my @Numbers = UnPack( n, $stringpack );  ## string input, array outp
+ut

  my $pack = pack("N N", 0, 99 );
  my $Numbers = UnPack( 1, $pack );
  say $Numbers;
  ( $Numbers ) = UnPack( 1, $pack );
  say $Numbers;
  my @Numbers = UnPack( 1, $pack );
  say $Numbers[0];
  ( @Numbers ) = UnPack( 1, $pack );
  say $Numbers[0];

 __END__

 result:
  1
  99
  99
  99
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On running this code, I could not reproduce my original statement, so I can only assume that I typed "$Numbers" instead of "@Numbers" when I wrote the test cases for 'sub UnPack'. But if I had put parenthesis around the scalar, I still would have gotten what I wanted ( list context ).

Thank you

"Well done is better than well said." - Benjamin Franklin

[reply]
[d/l]