incrementing hash values

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

I am trying to put values into a hash. I know that some will have the same keys, but different values. I am trying to increment the keys, which have numerical values, so that they won't overwrite each other but still be close in value. Somehow they keep getting overwritten.

if(defined $hash{$key}) {
$key = $key + .0000001 until !defined $hash{$key};
$hash{$key} = $value;
} else {
$hash{$key} = $value;
}
[download]

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Re: incrementing hash values by thor (Priest) on Dec 24, 2004 at 03:54 UTC
So what you're trying to do is store multiple values for a given key. If it were me, I'd use a hash of arrays. Like so: `push @{$hash{$key}}, $value` [download] Then, to extract them, you'd do something like this: `foreach my $key (keys %hash) { print "$key =>\n" foreach my $thing (@{$hash{$key}}) print "\t$thing\n"; } }` [download] thor `Feel the white light, the light within Be your own disciple, fan the sparks of will For all of us waiting, your kingdom will come`	[reply] [d/l] [select]
Re: incrementing hash values by Aristotle (Chancellor) on Dec 24, 2004 at 03:54 UTC
If `$value` can be undefined, your check will be testing for the wrong thing. Use exists instead of defined. But that's still klunky. Instead try `push @{ $hash{ $key } }, $value;` [download] Now the value for each key will be an array reference containing all the different values. Makeshifts last the longest.	[reply] [d/l]
Re: incrementing hash values by rev_1318 (Chaplain) on Dec 24, 2004 at 13:19 UTC
As others have pointed out, you probably should use a hash of arrays to store the values. I think the problem you are encountering, has to do with the representatio of floating point numbers. 100.0000001 may or may not be represented different internally as,say, 100.0000002, so you have no garantee that the keys will differ. Paul	[reply]
Re^2: incrementing hash values by Aristotle (Chancellor) on Dec 24, 2004 at 13:38 UTC
But his `until !defined $hash{$key}` fails so long as incrementing does not change the stringified value of `$key`. He might get an infinite loop, but it can't be the reason for entries in the hash getting overwritten. Makeshifts last the longest.	[reply]
Re: incrementing hash values by Anonymous Monk on Dec 24, 2004 at 23:39 UTC
How do you preform operations on the array then. For example, how would you do scalar. Also how do you print individual array elements without foreach? Thanks for the help.	[reply]