Array length within a hash

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

In my quest to improve QuizTaker.pl, I am trying to modify it, so that it can
accept questions that are a combination of multiple choice and true/false. What I
need to accomplish this (I think), is to be able to read the length of array that is
the value of a key within a hash. I have a small test function below, but it doesn't
quite work. It merely gives the memory address of the array. Any suggestions?

#!/usr/bin/perl -w
use strict;
 
my @value1=(1,2,3,4);
my @value2=(5,6);
my @value3=(7,8,9,0);
 
my %Hash = (Key1=>\@value1,Key2=>\@value2,Key3=>\@value3);
my @hasharraylengths=();
my $length = 0;
 
foreach my $key (keys %Hash){
  $length = $Hash{$key};
  push @hasharraylengths, $length;
}
 
my $l = @hasharraylengths;
for(my $x=0;$x<$l;$x++){
  print"Length of Value: $hasharraylengths[$x]\n";
}
[download]

TStanley
In the end, there can be only one!

Comment on Array length within a hash Download Code

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Re: Array length within a hash by suaveant (Parson) on Apr 23, 2001 at 21:37 UTC
either `$length = $#{$Hash{$key}}+1; # I think will work # or $length = @{$Hash{$key}}; #I know will work` [download] you must dereference the arrayref - Ant	[reply] [d/l]
Re: Array length within a hash by arturo (Vicar) on Apr 23, 2001 at 21:42 UTC
Try `foreach my $key (keys %Hash) { push @hasharraylengths, scalar @{$Hash{$key}}; }` [download] The idea : `$Hash{$key}` is an array reference. Dereference, with `@{}`, and force scalar ccntext with `scalar`. HTH	[reply] [d/l] [select]
Re: Array length within a hash by ton (Friar) on Apr 23, 2001 at 21:39 UTC
Replace this line: `$length = $Hash{$key};` [download] with this line: `$length = @{$Hash{$key}};` [download] Remember that you're storing references to the arrays as the values of your hash. You need to dereference those values... -Ton ----- Be bloody, bold, and resolute; laugh to scorn The power of man...	[reply] [d/l] [select]
Re: Array length within a hash by the_0ne (Pilgrim) on Apr 23, 2001 at 21:40 UTC
I think this is what you are getting at TStanley... `foreach my $key (keys %Hash){ $length = $#{$Hash{$key}} + 1; push @hasharraylengths, $length; }` [download] The output should be... Length of Value: 4 Length of Value: 2 Length of Value: 4	[reply] [d/l]