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How do I refer to an element of a hash of arrays as an array

by Anonymous Monk
on Mar 08, 2001 at 19:11 UTC ( #62964=perlquestion: print w/replies, xml ) Need Help??

Anonymous Monk has asked for the wisdom of the Perl Monks concerning the following question: (references)

I create a hash where each element refers to an array:

$h{'one'} = [1,2,3];
I can access the individual array elements o.k.:
print "$h{'one'}[1]\n";
prints "2" as I expect.

Why can't I access the entire array as if it were a regular array?
What don't I understand here:

my @a = $h{'one'}; print "$a[1]\n";
doesn't do what I expect.

Originally posted as a Categorized Question.

Replies are listed 'Best First'.
Re: How do I refer to an element of a hash of arrays as an array
by arturo (Vicar) on Mar 08, 2001 at 19:17 UTC

    Since hash values can only be scalars, the value is a reference to an array. That is, it's like a pointer. (Try print "$h{'one'}\n" and see what you get.)

    To get at the thing the reference points to, you need to explicitly dereference it. To get at the array, do

    my @a = @{ $h{one} };
    By enclosing something in the @{ } construction, you're saying that you want the array to which that reference points.

Re: How do I refer to an element of a hash of arrays as an array
by arhuman (Vicar) on Mar 08, 2001 at 19:17 UTC
    beccause $h{'one'} is a ref to an array !
    Use my @a=@$h{'one'};

    Originally posted as a Categorized Answer.

Re: How do I refer to an element of a hash of arrays as an array
by lachoy (Parson) on Mar 08, 2001 at 23:13 UTC

    Also, just for future debugging purposes, you might want to print out more than the second element of the array. Doing something like:

    my @a=$h{'one'}; print join( ' // ', @a );

    might have shown you something like:

    ARRAY(0x80e1310)

    which would hopefully be a giant red flag :-)

    Originally posted as a Categorized Answer.

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