Sort::Naturally -- sort lexically, but sort numeral parts numerically
@them = nsort(qw(
foo12a foo12z foo13a foo 14 9x foo12 fooa foolio Foolio Foo12a
));
print join(' ', @them), "\n";
Prints:
9x 14 foo fooa foolio Foolio foo12 foo12a Foo12a foo12z foo13a
(Or "foo12a" + "Foo12a" and "foolio" + "Foolio" and might be switched, depending on your locale.)
This module exports two functions, nsort and ncmp; they are used in implementing my idea of a "natural sorting" algorithm. Under natural sorting, numeric substrings are compared numerically, and other word-characters are compared lexically.
This is the way I define natural sorting:
use locale statement.foo => "foo", -1 foobar => "foo", -1, "bar" foo13 => "foo", 13, foo13xyz => "foo", 13, "xyz"
That's so that "foo" will come before "foo13", which will come before "foobar".
nsort or ncmp.This function takes a list of strings, and returns a copy of the list, sorted.
This is what most people will want to use:
@stuff = nsort(...list...);
When nsort needs to compare non-numeric substrings, it uses Perl's lc function in scope of a <use locale>. And when nsort needs to lowercase things, it uses Perl's lc function in scope of a <use locale>. If you want nsort to use other functions instead, you can specify them in an arrayref as the first argument to nsort:
@stuff = nsort( [
\&string_comparator, # optional
\&lowercaser_function # optional
],
...list...
);
If you want to specify a string comparator but no lowercaser, then the options list is [\&comparator, ''] or [\&comparator]. If you want to specify no string comparator but a lowercaser, then the options list is ['', \&lowercaser].
Any comparator you specify is called as $comparator->($left, $right), and, like a normal Perl cmp replacement, must return -1, 0, or 1 depending on whether the left argument is stringwise less than, equal to, or greater than the right argument.
Any lowercaser function you specify is called as $lowercased = $lowercaser->($original). The routine must not modify its $_[0].
Often, when sorting non-string values like this:
@objects_sorted = sort { $a->tag cmp $b->tag } @objects;
...or even in a Schwartzian transform, like this:
@strings =
map $_->[0]
sort { $a->[1] cmp $b->[1] }
map { [$_, make_a_sort_key_from($_) ]
@_
;
...you wight want something that replaces not sort, but cmp. That's what Sort::Naturally's ncmp function is for. Call it with the syntax ncmp($left,$right) instead of $left cmp $right, but otherwise it's a fine replacement:
@objects_sorted = sort { ncmp($a->tag,$b->tag) } @objects;
@strings =
map $_->[0]
sort { ncmp($a->[1], $b->[1]) }
map { [$_, make_a_sort_key_from($_) ]
@_
;
Just as with nsort can take different a string-comparator and/or lowercaser, you can do the same with ncmp, by passing an arrayref as the first argument:
ncmp( [
\&string_comparator, # optional
\&lowercaser_function # optional
],
$left, $right
)
You might get string comparators from Sort::ArbBiLex.
nsort) which I eventually discarded in favor of my algorithm. If you are having to naturally-sort very large data sets, and sorting is getting ridiculously slow, you might consider trying one of those discarded functions -- I have a feeling they might be faster on large data sets. Benchmark them on your data and see. (Unless you need the speed, don't bother. Hint: substitute sort for nsort in your code, and unless your program speeds up drastically, it's not the sorting that's slowing things down. But if it is nsort that's slowing things down, consider just:
if(@set >= SOME_VERY_BIG_NUMBER) {
no locale; # vroom vroom
@sorted = sort(@set); # feh, good enough
} elsif(@set >= SOME_BIG_NUMBER) {
use locale;
@sorted = sort(@set); # feh, good enough
} else {
# but keep it pretty for normal cases
@sorted = nsort(@set);
}
Copyright 2001, Sean M. Burke sburke@cpan.org, all rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
This program is distributed in the hope that it will be useful, but without any warranty; without even the implied warranty of merchantability or fitness for a particular purpose.
Sean M. Burke sburke@cpan.org
