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Re^3: Custom Sort An AoA

by kennethk (Abbot)
on Apr 02, 2014 at 18:09 UTC ( #1080808=note: print w/ replies, xml ) Need Help??


in reply to Re^2: Custom Sort An AoA
in thread Custom Sort An AoA

Lots of discussion has ensued since I checked out yesterday, but the most generic treatment I can think of is essentially pre-computing the comparison strings in two passes, so that you can be sure that your arguments are properly conditioned:

#!/usr/bin/perl use strict; use warnings; my @input = ( ['blah', 'asdf', 'foo', 'bar'], ['two'], ['zzz', 'def', 'ghi'], ['one'], ['mmm', 'def', 'ghi'], ['qqq', 'xyz', 'aaa'], ); my @list = do { my $max_array = 0; my $max_word = 0; for (@input) { $max_array = @$_ if @$_ > $max_array; for (@$_) { $max_word = length if length > $max_word; } } my $digit = 1 + int log($max_array)/log(10); my $format = "%$digit.d" . ("%-${max_word}s") x $max_array; my %cache = map {$_ => sprintf $format, 0+@$_, reverse(@$_), ( +'') x $max_array} @input; sort {$cache{$a} cmp $cache{$b}} @input; }; $" = "', '"; print "['@$_']\n" for @list;
My measurement approach means that it's no longer sensitive to delimiter choice, but of course this is a conservative approach to that since it assumes one $max_word for all terms. The empty string padding in the sprintf is just to silence warnings.

If you want a numerical sorting for elements in place of lexical sorting, you could swap "%-${max_word}s" in the format constructor to "%${max_word}.d" More complex the pattern, the more complex the construction - you can see how impressively the code exploded for just these changes. You could even support a mixed mode by flopping between "%-${max_word}s" and "%${max_word}.d" depending on looks_like_number EXPR.


#11929 First ask yourself `How would I do this without a computer?' Then have the computer do it the same way.


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