Active State Perl 5.6.1 build 626 Trashes hashes.

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

Has anyone else run into this? I using Active State perl 5.6.1 build 626 on Win2K ver 5.00.2195. If I predeclair pointers to two hashes it will merge the entries together? I'd like to use STRICT in my programing but this will pretty much kill it. Does anyone know any workarounds, patches, etc? Did I miss something basic? Below is the test code and its output.

# USING PREDECLARATIONS IT FAILS
my $x="";
my $another="";

print "WITH PREDECLS\n";
$x->{"FISH2"} = "FISH2";
$another->{"NONE"}="NONE";
foreach $item (keys %{$x}) {
  print "ELEMENTS: $item, $x->{$item}\n";
}

# NOT USING PREDECLARATIONS IT WORKS
print "\n\nWITHOUT PREDECLS\n";
$x2->{"FISH2"} = "FISH2";
$another2->{"NONE"}="NONE";
foreach $item (keys %{$x2}) {
  print "ELEMENTS: $item, $x2->{$item}\n";
}
[download]

Here is the output:

WITH PREDECLS
ELEMENTS: NONE, NONE
ELEMENTS: FISH2, FISH2


WITHOUT PREDECLS
ELEMENTS: FISH2, FISH2
[download]

Comment on Active State Perl 5.6.1 build 626 Trashes hashes. Select or Download Code

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Re: Active State Perl 5.6.1 build 626 Trashes hashes. by runrig (Abbot) on Aug 08, 2001 at 20:48 UTC
You are not predeclaring a hash nor a hash reference, you are predeclaring a scalar and giving it a character string as a value, and you cannot dereference a string. You want just either one of the following: `# A hash reference can be autovivified from an undefined value my $x; # Or assign an empty hash reference my $x = {};` [download] Update: Good point, John. I don't like to think about symbolic references, so I hardly ever consider them :-)	[reply] [d/l]
Re: Re: Active State Perl 5.6.1 build 626 Trashes hashes. by Anonymous Monk on Aug 08, 2001 at 21:55 UTC
i made the asumption that a pointer to a hash was not treated the same as a hash. That is,`$a->{'fish'} and $a{'fish'}` are these the same?If not how can I reference and deeferene both. (i.e. </CODE>$a=\{}<CODE>)	[reply] [d/l]
Re: Re: Re: Active State Perl 5.6.1 build 626 Trashes hashes. by runrig (Abbot) on Aug 08, 2001 at 23:30 UTC
First take a trip through 'perldoc perldata'. `$a->{'fish'}` is dereferencing the hash reference `$a`. `$a{'fish'}` is referencing an element of the hash `%a`. They are two different things using two different variables, `$a and %a`. And get ready to re-learn all this when Perl 6 comes around :-)	[reply] [d/l] [select]
Re: Re: Active State Perl 5.6.1 build 626 Trashes hashes. by John M. Dlugosz (Monsignor) on Aug 09, 2001 at 07:05 UTC
Actually, he is dereferenceing a string, since he's not using strict. Both variables "point" to the same place though, and that was doing confusing things.	[reply]
Re: Active State Perl 5.6.1 build 626 Trashes hashes. by rchiav (Deacon) on Aug 08, 2001 at 21:00 UTC
And for Yet Another Reason to `use strict;`.. if you had included it, you would have gotten the following error.. `Can't use string ("") as a HASH ref while "strict refs" in use at ./tr +y.pl line 11.` [download] line 11 after I made it run under strict is.. `x->{"FISH2"} = "FISH2";` [download] Rich	[reply] [d/l] [select]
Re: Active State Perl 5.6.1 build 626 Trashes hashes. by John M. Dlugosz (Monsignor) on Aug 09, 2001 at 07:03 UTC
You're not predeclaring a hash. I think you meant: `my $x= {}; # reference to empty hash` [download] you assigned $x a string, which is, well, not a hash reference, as pointed out in other posts. If you were thinking "empty" but just getting the syntax wrong, use {} where you had "".	[reply] [d/l]