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Cant use string(_) as array ref..!!

by reaper9187 (Scribe)
on Jan 24, 2013 at 09:07 UTC ( #1015108=perlquestion: print w/ replies, xml ) Need Help??
reaper9187 has asked for the wisdom of the Perl Monks concerning the following question:

Hi everyone ..
I'm working on a problem.. Jus need some help with the following code:
use Data::Dumper; use strict; our (@a,$c,$key,$bar); #!/usr/bin/perl use strict; use warnings; use Data::Dumper; use Tk; use Tk::Chart::Lines; my $mw = MainWindow->new( -title => 'Tk::Chart::Lines example', -background => 'white', ); my $chart = $mw->Lines( -title => 'My graph title', -xlabel => 'X Label', -ylabel => 'Y Label', )->pack(qw / -fill both -expand 1 /); @a = qw/Mon Tue Wed Thurs/; foreach $key(@a) { push(@{${$key}[0]},1,33); push(@{${$key}[0]},22,11); push(@{${$key}[1]},2,5); push(@{${$key}[2]},3,4); } $c ="Mon"; # Add a legend to the graph my @legends = ( 'legend 1', 'legend 2', 'legend 3' ); $chart->set_legend( -title => 'Title legend', -data => \@legends, -titlecolors => 'blue', ); # Add help identification $chart->set_balloon(); print Dumper(@$c); # Create the graph $chart->plot( @$c ); MainLoop();
I get the error.. "Cant use string "Mon" as array ref while strict refs in use ... "

How do i solve this issue .. Please help ..!!!

Comment on Cant use string(_) as array ref..!!
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Re: Cant use string(_) as array ref..!!
by Anonymous Monk on Jan 24, 2013 at 09:14 UTC
Re: Cant use string(_) as array ref..!!
by choroba (Abbot) on Jan 24, 2013 at 09:17 UTC
    Let's analyze it. @a is an array of strings. Next, you iterate over it with
    foreach $key (@a)
    So, $key is a string, "Mon" in the first iteration. Then, you use the expression
    ${$key}[0]
    It tries to dereference $key as an array reference, but it is not: it is a scalar string. Hence the error.
    لսႽ ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ
Re: Cant use string(_) as array ref..!!
by reaper9187 (Scribe) on Jan 24, 2013 at 09:22 UTC
    Can you please suggest a way to remove this issue ????

      Just for clarification can you tell me what you are doing here ? push(@{${$key}[0]},1,33);

Re: Cant use string(_) as array ref..!!
by thundergnat (Deacon) on Jan 24, 2013 at 14:33 UTC

    Update: changed 'indirect' to 'symbolic' as that is what I meant, but blanked out on while I was composing my post.

    First off, Kudos for using the strict and warnings pragmas. They will really help you catch typos and silly errors in your script.

    push(@{${$key}[0]},1,33); push(@{${$key}[0]},22,11); push(@{${$key}[1]},2,5); push(@{${$key}[2]},3,4);

    Ok you are trying to use indirect symbolic referencing to autovivify your hashes and that is not allowed under the strict pragma. You would probably be better off just predeclaring a single hash and use the day names as keys. Did you really want a 4 element array at index 0 and 2 element arrays elsewhere? Tk::Chart::Lines is going to complain about that. Anyway see if this clears anything up for you.

    #!/usr/bin/perl use strict; use warnings; use Data::Dumper; use Tk; use Tk::Chart::Lines; my $mw = MainWindow->new( -title => 'Tk::Chart::Lines example', -background => 'white', ); my $chart = $mw->Lines( -title => 'My graph title', -xlabel => 'X Label', -ylabel => 'Y Label', )->pack(qw / -fill both -expand 1 /); my @a = qw/Mon Tue Wed Thurs/; my %days; foreach my $key (@a) { push @{$days{$key}}, [1, 33]; push @{$days{$key}}, [22, 11]; push @{$days{$key}}, [2, 5]; push @{$days{$key}}, [3, 4]; } my $c ='Mon'; # Add a legend to the graph my @legends = ( 'legend 1', 'legend 2', 'legend 3' ); $chart->set_legend( -title => 'Title legend', -data => \@legends, -titlecolors => 'blue', ); # Add help identification $chart->set_balloon(); #print Dumper \$days{$c}; # Create the graph $chart->plot( $days{$c} ); MainLoop;

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