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

I have a Hash list : 
%category = (
    Anim => 'Animation Projects',
    Build => 'Building/Structural Projects',
    CAD => 'CAD/CAM Engineering Projects',
    
);

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Now I would like to search the KEYS and compare to a $variable, and print the VALUE for the matched $variable.

Another words compare ($variable = Anim) to the Hash and print just the value for that KEY (Animation Projects)

I keep printing every VALUE when it finds a match, not just the matched VALUE..

Thanks in advance...

______SysAdm

Replies are listed 'Best First'.
Re: Matching a KEY in a HASH
by merlyn (Sage) on May 14, 2001 at 19:42 UTC
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      I must not be making myself clear...

      The $variable = "" could = Anim or CAD or anything in the list...

      My question is ... How do I search the HASH to match the $variable, but print the VALUE only...

      make sense?
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        I must not be making myself clear.

        The point of a hash is that a hash itself can find a value for a given key trivially. 

        $value_you_are_looking_for = $category{$variable};

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        There's no searching required. If there's an element with a key of $variable, then $value_you_are_looking_for has it. Otherwise, it gets undef.

        -- Randal L. Schwartz, Perl hacker

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Re: Matching a KEY in a HASH
by larsen (Parson) on May 14, 2001 at 19:47 UTC
    The purpose of a hash (among other things) is avoiding exaustive searches. So you could write something like: 
    $category{'Anim'};

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    in order to obtain Animation Projects. I suggest reading perldata.

    Also, if you want to match keys using a regular expression, read this (Tie::Hash::Regex by davorg).

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Re: Matching a KEY in a HASH
by flocto (Pilgrim) on May 14, 2001 at 20:55 UTC
    Ok, the other comments obviously misunderstood what your point was, but don't worry, it's still trivial:
    my %hash = ( 'Anim' => 'Animation',
             ...
             'Test' => 'Whatever');
my $key = 'Anim';

print $key if $hash{$key};

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    Regards, octo
    --
    GED/CC d-- s:- a--- C++(+++) UL+++ P++++$ L++>++++ E--- W+++@ N o? K? w-- O- M-(+) V? !PS !PE !Y PGP+(++) t-- 5 X+ R+(+++) tv+(++) b++@ DI+() D+ G++ e->+++ h!++ r+(++) y+
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Re: Matching a KEY in a HASH
by suaveant (Parson) on May 14, 2001 at 21:23 UTC
    You want to match a key based on a substring? and print all values that match? You can use the Tie::Hash mentioned above or just to match a substring you can do... 
    for(keys %category) {
  print "$category{$_}\n" if /\Q$variable\E/i;
}

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    the \Q \E makes sure that you match the characters in $variable the way they are, (other a \ could screw you all up, or a . or a *, etc) and the i at the end makes it case-insensitive (often good in substring matching). Does that help?
                    - Ant
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[d/l]
      Here's the code I'm currently using: 
      %category = (
    Anim => 'Animation Projects',
    Build => 'Building/Structural Projects',
    CAD => 'CAD/CAM Engineering Projects',
    );


    my $value;
              $value = (sort values %category);
    print "$value" if (exists($category{"$form{'USER_INPUT'}"})) ;

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      It prints EVERY $value instead of just the $value for the matching $form{'USER_INPUT'}.

      I hope my question is now clearer and makes more sense..
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[d/l]
        Yes, stop getting all the values, when all you want is one value. Use the code I've posted twice in this thread, as have others.

        -- Randal L. Schwartz, Perl hacker

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        Ummm, first things first... 
        $value = (sort values %category);

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        will store the last value of the sorted list of values in $value, this is most likely not what you want. You are looking to print the value of %category that the key matches $form{'USER_INPUT'}? then use.. 
        print $category{$form{'USER_INPUT'} if $category{$form{'USER_INPUT'};

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        do you just want the value of Anim if the user inputs Anim, or do you want Build AND CAD when the user inputs 'd'?
                        - Ant
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        As merlyn said, looks like you are trying to grab all the 'values' with the $value = (sort values %category); statement.

        If you just use

        print "$category{$form{'USER_INPUT'}}"
   if exists $category{$form{'USER_INPUT'}};

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        everything should work fine. (At least it did for me... :)

        D a d d i o

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