hash Querry

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

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Re: hash Querry by psini (Deacon) on Sep 09, 2008 at 13:22 UTC
Now that you have got the mandatory advices, let's see: `my %hash={}` Apart from the missing semicolon at the end of this line, the statement is faulty because you define a hash "%hash" and assign to it a hash reference {}! In order to initialize an empty hash you can simply use `my %hash;` or `my %hash=();` assigning to it an empty list. `$hash{ONE}='malay';` This one is good, assigns to the element "ONE" of the hash %hash. `$hash->{TWO}='manab';` This one is less good, tries assigning to the element "TWO" of the hash reference $hash which is undefined. Rule One: "Do not act incautiously when confronting a little bald wrinkly smiling man."	[reply] [d/l] [select]
Re: hash Querry by svenXY (Deacon) on Sep 09, 2008 at 13:05 UTC
Hi, `use strict;` is your friend. If you put it in front of your statements, you get something like `Global symbol "$hash" requires explicit package name at 710071.pl line + 5. BEGIN not safe after errors--compilation aborted at 710071.pl line ...` [download] This is because the first assignments assigns 'malay' to the hash %hash (with key 'ONE'), whereas the second tries to assign 'manab' to an anonymous hash that is referenced by the reference called $hash (that is not explicitely created and therefore errs with "strict" on). That said, the second assignment does not add an key/value pair to your %hash! Regards, svenXY	[reply] [d/l] [select]
Re: hash Querry by wfsp (Abbot) on Sep 09, 2008 at 13:03 UTC
Add `use strict; use warnings;` [download] to the top of your script and see what happens.	[reply] [d/l]
Re: hash Querry by dHarry (Abbot) on Sep 09, 2008 at 13:06 UTC
I did: `Reference found where even-sized list expected at ... Can't use an undefined value as a HASH reference at ...` [download] :-)	[reply] [d/l]