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printing hash produce errors

by Xfiles (Initiate)
on Jun 02, 2013 at 12:06 UTC ( #1036580=perlquestion: print w/ replies, xml ) Need Help??
Xfiles has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to execute the following line of code :
#!usr/bin/perl use strict ; use warnings ; my %hash = {'perl' => 1 , 'C' => 0} ; foreach my $key(sort keys %hash) { print "$key : $hash{$key} \n" ; }
but it gives me the following error :
Reference found where even-sized list expected at perl.pl line 9. Use of uninitialized value $hash{"HASH(0x98bf7ec)"} in concatenation ( +.) or string at perl.pl line 12. HASH(0x98bf7ec) :
so what is exactly the problem ?

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Re: printing hash produce errors
by bart (Canon) on Jun 02, 2013 at 12:18 UTC
    Your problem is that you're mixing up hashes (%hash) with hash references ({ key => value }) -- note the braces.

    Replace the braces with parens and it should work:

    my %hash = ('perl' => 1 , 'C' => 0) ;
    This produces a flat list, not a hashref, which is exactly what assignment to a hash wants.

    Alternatively you could use a hashref (= a scalar pointing to a hash) everywhere:

    my $hash = {'perl' => 1 , 'C' => 0} ; foreach my $key(sort keys %$hash) { print "$key : $hash->{$key} \n" ; }
      that's it , thanks .

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