http://qs321.pair.com?node_id=130851


in reply to Testing array of hash values

It looks like this is intended to be a CGI, and yet it doesn't emit the correct response header, so I'll assume this is just a code fragment.

What, exactly, do you expect   @p{'eyes', 'hair', 'etc'} =(); to do? It rather looks like a syntax error to me. If you're trying to pre-load a hash with keys, you might try 

  my %p;
  $p{$_} = undef for qw(eyes hair etc);

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But that begs the question of what your do_print is trying to do, since   @p{ 'eyes', 'hair', 'etc' } results in a three element array, with each element being undef. Assuming that you're trying to return the heading if and only if any one of the elements is present, you could do 
  sub do_head {
       my($heading, @data) = @_;

      return "<h4>$heading</h4>" if grep { defined($_) } @data;
      return "";
  }

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Replies are listed 'Best First'.
Another posible initializer
by Fletch (Bishop) on Dec 11, 2001 at 07:32 UTC

    He may have been trying for: 

    my %p;
@p{ qw( eyes hair etc ) } = ( undef ) x 3;

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    Of course that's crufty in that you have to hard code in the number of elements.

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      Actually, 
      my %p;
@p{'eyes', 'hair', 'etc'} = ();

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      is a common idiom for using a hash slice to load a hash with keys and undef values.
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[d/l]

        You're quite right. I was thinking more of: 

        my %p;
@p{ qw( a b c ) } = (1)x3;

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        where you're initializing to a given value (like 1 or "on") rather than undef.

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Re: Re: Testing array of hash values
by legLess (Hermit) on Dec 11, 2001 at 10:33 UTC
    Yes, it's a fragment, but it runs as it should from the command line. The line 
    @p{'eyes', 'hair', 'etc'} =();

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    is just to show that those keys are empty. It was indeed the undef that was getting me. Your code works. Thanks.
    --
    man with no legs, inc.
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