in reply to Print name of variable to STDOUT?

Is the "additional level of complexity just for this" just for diagnostic purposes, or is it something sneeky that the "user" ends up seeing?

If it is for diagnostic purposes you might want to take a look at the debugging support in Perl rather than poluting your code with diagnostic lint that obfusicates intent and probably adds bugs of its own.

For a very brief overview of the debugger see Using the Perl Debugger in the Tutorials section.

DWIM is Perl's answer to Gödel

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Re^2: Print name of variable to STDOUT?
by bowei_99 (Friar) on Aug 08, 2006 at 22:44 UTC
    It's for both debugging and to clarify the output. Since this will go into a report, I'll need a lookup hash mapping the variable names with userfriendly descriptions, but initially, just the variable names should do.

    I thought it might help if I posted my code, to show the context. Here it is:

    
sub GetStats {
        my $ref_files = shift @_;
        my (%lkup_by_who, %lkup_by_how, %lkup_by_from, %lkup_by_ftp);

        foreach my $file (@$ref_files) {
                open "LAST", "<", $file
                        or croak "Cannot open file $file - $!\n";
                print "Reading file $file ... \n";
                while (<LAST>) {
                        my ($who, $how, $from, @junk) = split (/\s+/);
                        next if (!$who or !$how or !$from);
                        next if (/wtmp begins/);
                        if ($how eq "console") {
                                $how = $from;
                                next;
                        }
                        $from =~ s/:\d+(\.\d+)?//g;
                        $lkup_by_who{$file}{"$who"}++;
                        $lkup_by_from{$file}{"$from"}++;
                        if ($how eq "ftp") {
                                $lkup_by_ftp{$file}{"$who"}++;
                        }
                }
                close (LAST);
        }
        return (\%lkup_by_who, \%lkup_by_from, \%lkup_by_ftp);
}

    [download]
    As you can see, it returns an array of hash of hashes. To avoid unnecessary complexity, I want to avoid putting it in one big hash, with keys 'who', 'from', and 'ftp'. Can I tell perl to output the variable names %lkup_by_who, \%lkup_by_from, \%lkup_by_ftp? I know that these variables are only defined within the subroutine, and so I'd have to put it in one big hash or print the information within the subroutine for it work.

    -- Burvil

[reply]
[d/l]

      You could use a hash to hold onto the hashes with very little extra work:

      sub GetStats {
        my $ref_files = shift @_;
        my %lkup_by = (who => {}, how => {}, from => {}, ftp => {});

        foreach my $file (@$ref_files) {
                ...
                while (<LAST>) {
                        ...
                        $lkup_by{who}{$file}{$who}++;
                        $lkup_by{from}{$file}{$from}++;
                        if ($how eq "ftp") {
                                $lkup_by{ftp}{$file}{$who}++;
                        }
                }
                close (LAST);
        }
        return ($lkup_by{who}, $lkup_by{from}, $lkup_by{ftp});
}

      [download]

      I don't see where you need to get at the names however. Note too that you don't need to interpolate variables into strings, just use them directly.

      DWIM is Perl's answer to Gödel
[reply]
[d/l]

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