On 4/4/06, Lawrence Statton <[EMAIL PROTECTED]> wrote:
> > Is there a nice clean perl way to test to see if only one key of a hash
> > has data?
> >
> > %some_hash = ( key1 => 1, key2 => 2 ); should fail the test
> > %some_hash = ( key2 => 2 ); should pass the test
> > %some_hash = ( key1 => 1 ); should pass the test
> > %some_hash = ( key1 => 1, key2 => 2, key3 => 3 ); should fail the test
> > %some_hash = ( key2 => 2 ); should pass the test
> > %some_hash = ( key1 => 1 ); should pass the test
> > %some_hash = ( key2 => 2, key3 => 3 ); should pass the test
> > %some_hash = ( key1 => 1, key3 => 3 ); should pass the test
> >
> > Basically I can many more keys in the hash but two of the keys have to
> > be exclusive.
> >
>
> You really could have said that a LOT better... It took several
> re-readings, and finally "what's the difference between test-cases 1,
> 7 and 8?" to understand what you meant.
>
> How 'bout
>
> Given a hash %hash with many keys ( qw / key1 key2 key3 keyn / )
> how do I test that only one of the values $hash{key1} or $hash{key2} are
> defined?
>
> if ( exists $hash{key1} and exists $hash{key2} ) {
> warn "fail";
> } else {
> warn "succeed";
> }
You've said two differnt things here, though, and they may be
important to the OP, although he hasn't been very clear. If you want
to know whether a value is defined, you don't use exists, you use
defined. Consider
#!/usr/bin/perl
use warnings;
use strict;
my %hash = (
0 => 0,
1 => 1,
2 => 2,
3 => undef,
4 => ''
);
foreach my $key (keys %hash) {
print "key $key ";
print "exists" if exists $hash{$key};
print ", is defined" if defined $hash{$key};
print ", is true" if $hash{$key};
print "\n";
}
print "2 & 3 both exist\n" if exists $hash{2} && exists $hash{3};
print "2 & 3 aren't both defined\n" unless defined $hash{2} &&
defined $hash{3};
print "2 & 3 aren't both true\n" unless $hash{2} && $hash{3};
print "5 didn't even come to the party\n" unless exists $hash{5};
The first step is for OP to decide what question he really wants to
ask about his data.
HTH,
-- jay
--------------------------------------------------
This email and attachment(s): [ ] blogable; [ x ] ask first; [ ]
private and confidential
daggerquill [at] gmail [dot] com
http://www.tuaw.com http://www.dpguru.com http://www.engatiki.org
values of β will give rise to dom!
