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

Hi all, The following code works fine to print out values in a hash. But how can i alter it so that it prints out those values that dont exist in the hash? 
%naccess = map { /^\s+\S+\s+\S+\s+(\S+)/; ($1 => $_) } <IN2>;

close (IN2);

while (<IN>) {

chomp;

/^\s+(\S+)/;
print OUT ($naccess{$1}) if (exists($naccess{$1}));

        }

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Re: hash question
by ikegami (Patriarch) on Nov 21, 2004 at 21:25 UTC

    print OUT ($1) if (!exists($naccess{$1}));
    or
    print OUT ($1) unless (exists($naccess{$1}));

    Although it's not quite proper English, it reads rather nicely if you remove the optional parens:
    print OUT ($1) if not exists $naccess{$1};

    Update: It's useless to print $naccess{$1} if it doesn't exist! I substituted $naccess{$1} with the key ($1).

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      these are what i thought might work, but do not!
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        oops, fixed.
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Re: hash question
by pg (Canon) on Nov 21, 2004 at 21:36 UTC
    "print OUT ($naccess{$1}) if (exists($naccess{$1}));"

    To make your code more robust, you better first check whether $1 is actually set, before you check whether it exists in the hash.

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      i know that the $1 is being called correctly. prints the values i want
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        this is my code 
        $first = shift@ARGV;
$second = shift@ARGV;

open (IN, "<$first");
open (IN2, "<$second");
open (OUT, ">NACCESS");


%naccess = map { /^\s+\S+\s+\S+\s+(\S+)/; ($1 => $_) } <IN2>;

close (IN2);

while (<IN>) {

chomp;

/^\s+(\S+)/;
print OUT ($1) unless (exists($naccess{$1}));
        }
close (IN);

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        IN2 FILE 
           1    59    49   0.0    0    100.0    0.0
   1    60    50   0.0    0    100.0    0.0

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        IN FILE 
           112  104.35  141.94  
   115   22.34   29.13

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