hash defined?

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

Hello monks, I want to find out if a key in a hash is defined. when I try the following code from http://perldoc.perl.org/functions/exists.html

print "Exists\n" if exists $hash{$key};
[download]

when i have;

use strict; use warnings; use diagnostics;
[download]

I get a "use of uninitialized value warning" I know some values are uninitialised, and wanted to use the above function to seperate them out. Is there a way to do this without being warned!? Many thanks for your thoughts.

Comment on hash defined? Select or Download Code

Replies are listed 'Best First'.
Re: hash defined? by Roy Johnson (Monsignor) on Mar 06, 2008 at 20:41 UTC
`print "Exists\n" if defined $key and exists $hash{$key};` Caution: Contents may have been coded under pressure.	[reply] [d/l]
Re: hash defined? by locked_user sundialsvc4 (Abbot) on Mar 06, 2008 at 22:28 UTC
I simply use `defined()`. If the key does not exist in the hash, the result is `undef.` If the key does exist and its present value is `undef`, the result will be the same. “It's what I want” in either case: although the cases are distinct, I don't have to care.
Re: hash defined? by whakka (Hermit) on Mar 06, 2008 at 20:47 UTC
I would say first if you want to see if a key in a hash is defined, use `defined` and not `exists`. However I don't get such a warning with your code whether the key is defined or not. Is that right?	[reply] [d/l] [select]