First Value in hash

techie411 has asked for the wisdom of the Perl Monks concerning the following question:

Replies are listed 'Best First'.
Re: First Value in hash by Corion (Patriarch) on Jan 08, 2008 at 09:21 UTC
"How do I make a single step?" "You start walking and then stop after the first step." `foreach $key (sort(keys %in)) { print MAIL "\t", $key, " = \t", $in{$key}, "\n"; last; } close MAIL;` [download] Or, as an approach that is a bit more verbose yet without the loop: `my @keys = sort keys %in; print MAIL "\t", $key[0], " = \t", $in{$key[0]}, "\n";` [download] Or, as an approach that is a bit more transparent and doesn't use the array: `(my $first) = sort keys %in; print MAIL "\t", $key, " = \t", $in{$key}, "\n";` [download]	[reply] [d/l] [select]
Re: First Value in hash by ysth (Canon) on Jan 08, 2008 at 09:59 UTC
`keys %in; #reset the iterator to the beginning of the hash my $firstkey = each %in; print MAIL "\t", $firstkey, " = \t", $in{$firstkey}, "\n";` [download] but since hashes are not ordered (unless tied to some class that enforces some ordering), which key is "first" isn't very meaningful. If you meant the key that sort makes be first, `my $firstkey = (sort(keys %in))[0];` [download] is one way. -- CollegeGear.com - more than just college gear (though, yes, we have college-branded teddy bears)	[reply] [d/l] [select]
Re: First Value in hash by bingos (Vicar) on Jan 08, 2008 at 09:20 UTC
TIMTOWTDI, but perhaps: `my $key = ( sort keys %in )[0];` [download]	[reply] [d/l]
Re: First Value in hash (List::Util::minstr()) by lodin (Hermit) on Jan 08, 2008 at 11:18 UTC
Instead of sorting the keys, which is unnecessary work, you can use List::Util's `minstr` subroutine. `use List::Util 'minstr'; my $first_key = minstr(keys %in);` [download] lodin	[reply] [d/l] [select]
Re: First Value in hash by apl (Monsignor) on Jan 08, 2008 at 10:52 UTC
My answer is, essentially, "what ysth said". The purpose of a hash is to provide fast access to a specific key, rather to store information in a sequential order. You can always store the order an item was entered, and scan for it later. That is: `$in{$key}{rank} = $nthElement++;` Followed by `foreach $key (sort(keys %in)) { print MAIL "\t", $key, " = \t", $in{$key}, "\n" if $in{$key}{rank} == 0; }` [download]	[reply] [d/l] [select]