tc1364 has asked for the wisdom of the Perl Monks concerning the following question:

The code is reading in several files one at a time and either creating a key value pair or amending the value for the key if it exists. The trouble is keys with single values only print out the key. I understand that the value needs to be associated if the key doesn't exist but my attempts have not worked. Can you please point out my blunder? 
            while(<RPT>)
            {
                chop;
                if ($_ =~ s/^(\D+.*\d{4}\s+)(\D+.*)(\w{11})$/$1 $2 $3/
+)
                {
                    $msg = $2;
                    fmt_rpt($msg);
                    $key = "$3";
                    if (exists($analysis{$key}))
                    {
                    $val .= "$msg";
                    }
                    else
                    {
                    #$val = "$msg";
                    $analysis{$key} = "$val";
                    }
                }
                else
                {
                    print "Program Error 2\n";
                    exit 1;
                }

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20041119 Janitored by Corion: Fixed broken code tag

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Re: Hash Trouble
by ikegami (Patriarch) on Nov 19, 2004 at 17:17 UTC

    chop should be chomp.

    "$3" should be $3.

    "$msg" should be$msg.

    "$val" should be $val.

    Why are you using a substitution instead of if ($_ =~ /^(\D+.*\d{4}\s+)(\D+.*)(\w{11})$/?

    $_ =~ can be omitted.

    It's bad to use $1, $2, etc after calling a function after they've been set.

    fmt_rpt($msg) should probably be $msg = fmt_rpt($msg).

    And the answer to your question: $val .= "$msg"; should $analysis{$key} .= $msg. I'm not sure if that's exactly what you want, but you never save $val into the hash, so your problem is definitely here.

    $val is used but never set in the else part of the if.

    And the answer to your question: $val .= "$msg"; should $analysis{$key} .= $msg. I'm not sure if that's exactly what you want, but you never save $val into the hash, so your problem is definitely here.

    $1 is never used. I'm going to leave the capture in the code below, in case you plan on using $1.

    Fixed code:

                while(<RPT>)
            {
                chomp;
                if (/^(\D+.*\d{4}\s+)(\D+.*)(\w{11})$/)
                {
                    $key = $3;
                    $msg = $2;

                    # Maybe should be: $msg = fmt_rpt($msg);
                    fmt_rpt($msg);

                    if (exists($analysis{$key}))
                    {
                        $analysis{$key} .= $msg;
                    }
                    else
                    {
                        $analysis{$key} = $msg;
                    }
                }
                else
                {
                    print "Program Error 2\n";
                    exit 1;
                }

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      Thank you for all of the information! The new code was missing the association of $val in the else statement so it was added and the new code looks like: $1 = time stamp $2 = error message $3 = unique identifer I am not sure if the time stamp information is going to be used. 
      
            while(<RPT>)
            {
                chomp;
                if (/^(\D+.*\d{4}\s+)(\D+.*)(\w{11})$/)
                {
                    $key = $3;
                    $msg = $2;
                    fmt_rpt($msg);
                    if (exists($analysis{$key}))
                    {
                    $analysis{$key} .= $msg;
                    }
                    else
                    {
                    $val = $msg;
                    $analysis{$key} = $val;
                    }
                }
                else
                {
                    print "Program Error 2\n";
                    exit 1;
                }

      [download]
      For me I would rather build one hash table instead of multiple hash tables and then merging them. To me it seems like a waste what are your thoughts?
[reply]
[d/l]
        The new code was missing the association of $val

        Not at all. There's no reason to do
        $val = $msg;
        $analysis{$key} = $val;
        when
        $analysis{$key} = $msg;
        suffices.

        For me I would rather build one hash table instead of multiple hash tables and then merging them. To me it seems like a waste what are your thoughts?

        To which multiple hashes are you refering? You mean if you if you were to keep the timestamp? You could do something like:

                    while(<RPT>)
            {
                chomp;
                if (/^(\D+.*\d{4}\s+)(\D+.*)(\w{11})$/)
                {
                    my $timestamp = $1;
                    my $msg       = $2;
                    my $key       = $3;
                    fmt_rpt($msg);
                    if (exists($analysis{$key}))
                    {
                        $analysis{$key}[1] .= $msg;
                    }
                    else
                    {
                        $analysis{$key} = [ $timestamp, $msg ];
                    }
                }
                else
                {
                    print "Program Error 2\n";
                    exit 1;
                }

        [download]

        See perllol for details. This would be a HoA (Hash of Arrays), which is similar to the mentioned AoA (Array of Arrays).

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