Parsing hash reference as argument for subroutine

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

Hi Monks, I´m trying to pass a matrix reference as argument to a printmatrix subroutine.. unfortunately without succes.. the matrix was stored in the variable $matrix={} as a hash of hashes $matrix->{$key}->{$value}; here´s what i have done.. any suggestions?

sub Matrix {
foreach my $key (@aminos){
        foreach my $key2 (@aminos){
            $matrix->{$key}->{$key2}= $ratesfromfreq->{$key}->{$key2}*
+$factor;
        }
        $matrix->{$key}->{$key} += (1-$factor);
}

 
sub printMatrix1 {
    my $matrix2;
    ($matrix2) = @_;
    foreach my $key (sort keys %$matrix2){
        print $key."  "x2;
        foreach my $key2 (sort keys %{$matrix2->{$key}}){
            printf("%.5f  ", $matrix2->{$key}->{$key2});
        }
        print "\n"x2;
    }
}

my $P= Matrix();
printMatrix($P);
[download]

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Re: Parsing hash reference as argument for subroutine by choroba (Cardinal) on Jan 06, 2014 at 11:48 UTC
I added `use strict; use warnings;` and fixed the reported problems. I also added some whitespace to make the code more readable and populated some variables to get any output: #!/usr/bin/perl use warnings; use strict; my @aminos = qw(a b c); my $matrix; my $ratesfromfreq = {a => {a => 2, b => 1, c => 3}, b => {a => 3, b => 2, c => 4}, c => {a => .4, b => .3, c => .1}}; my $factor = .2; sub Matrix { for my $key (@aminos) { for my $key2 (@aminos) { $matrix->{$key}{$key2} = $ratesfromfreq->{$key}{$key2} * $ +factor; } $matrix->{$key}{$key} += (1 - $factor); } return $matrix; } sub printMatrix1 { my $matrix2; ($matrix2) = @_; for my $key (sort keys %$matrix2) { print $key . " " x 2; for my $key2 (sort keys %{ $matrix2->{$key}} ) { printf '%.5f ', $matrix2->{$key}{$key2}; } print "\n" x 2; } } my $P= Matrix(); printMatrix1($P); [download] Output: `a 1.20000 0.20000 0.60000 b 0.60000 1.20000 0.80000 c 0.08000 0.06000 0.82000` [download] لսႽ† ᥲᥒ⚪⟊Ⴙᘓᖇ Ꮅᘓᖇ⎱ Ⴙᥲ𝇋ƙᘓᖇ	[reply] [d/l] [select]
Re^2: Parsing hash reference as argument for subroutine by madM (Beadle) on Jan 06, 2014 at 12:31 UTC
thankyou!!	[reply]
Re: Parsing hash reference as argument for subroutine by Eily (Monsignor) on Jan 06, 2014 at 11:54 UTC
You should use strict and warnings, it would have helped you avoid some trouble. $matrix is not declared, you should have a `my $matrix = {};` at the beginning of the function. This function does not return $matrix. But then again, there are three { block opener but only two } block ends, this doesn't even compile. To see what's inside a nested data structure (like a hash of hashes), you can use Data::Dumper like this : `use Data::Dumper; #At the top of the file ... print Dumper $P;` [download] And at last, you probably want to read perldsc	[reply] [d/l] [select]