package Sort::Key::Top;
our $VERSION = '0.08';
use strict;
use warnings;
require Exporter;
our @ISA = qw(Exporter);
our @EXPORT_OK = qw( top
ltop
ntop
itop
utop
rtop
rltop
rntop
ritop
rutop
keytop
lkeytop
nkeytop
ikeytop
ukeytop
rkeytop
rlkeytop
rnkeytop
rikeytop
rukeytop
part
lpart
npart
ipart
upart
rpart
rlpart
rnpart
ripart
rupart
keypart
lkeypart
nkeypart
ikeypart
ukeypart
rkeypart
rlkeypart
rnkeypart
rikeypart
rukeypart
partref
lpartref
npartref
ipartref
upartref
rpartref
rlpartref
rnpartref
ripartref
rupartref
keypartref
lkeypartref
nkeypartref
ikeypartref
ukeypartref
rkeypartref
rlkeypartref
rnkeypartref
rikeypartref
rukeypartref
topsort
ltopsort
ntopsort
itopsort
utopsort
rtopsort
rltopsort
rntopsort
ritopsort
rutopsort
keytopsort
lkeytopsort
nkeytopsort
ikeytopsort
ukeytopsort
rkeytopsort
rlkeytopsort
rnkeytopsort
rikeytopsort
rukeytopsort
atpos
latpos
natpos
iatpos
uatpos
ratpos
rlatpos
rnatpos
riatpos
ruatpos
keyatpos
lkeyatpos
nkeyatpos
ikeyatpos
ukeyatpos
rkeyatpos
rlkeyatpos
rnkeyatpos
rikeyatpos
rukeyatpos
head
lhead
nhead
ihead
uhead
rhead
rlhead
rnhead
rihead
ruhead
keyhead
lkeyhead
nkeyhead
ikeyhead
ukeyhead
rkeyhead
rlkeyhead
rnkeyhead
rikeyhead
rukeyhead
tail
ltail
ntail
itail
utail
rtail
rltail
rntail
ritail
rutail
keytail
lkeytail
nkeytail
ikeytail
ukeytail
rkeytail
rlkeytail
rnkeytail
rikeytail
rukeytail
);
for ((@EXPORT_OK)) {
my $slot = $_;
$slot =~ s/key/slot/ and
push @EXPORT_OK, $slot;
}
require XSLoader;
XSLoader::load('Sort::Key::Top', $VERSION);
1;
__END__
=head1 NAME
Sort::Key::Top - select and sort top n elements
=head1 SYNOPSIS
use Sort::Key::Top (nkeytop top);
# select 5 first numbers by absolute value:
@top = nkeytop { abs $_ } 5 => 1, 2, 7, 5, 5, 1, 78, 0, -2, -8, 2;
# ==> @top = (1, 2, 1, 0, -2)
# select 5 first numbers by absolute value and sort accordingly:
@top = nkeytopsort { abs $_ } 5 => 1, 2, 7, 5, 5, 1, 78, 0, -2, -8, 2;
# ==> @top = (0, 1, 1, 2, -2)
# select 5 first words by lexicographic order:
@a = qw(cat fish bird leon penguin horse rat elephant squirrel dog);
@top = top 5 => @a;
# ==> @top = qw(cat fish bird elephant dog);
=head1 DESCRIPTION
The functions available from this module select the top n elements from a list
using several common orderings and custom key extraction procedures.
They are all variations around
keytopsort { CALC_KEY($_) } $n => @data;
In array context, this function calculates the ordering key for every
element in C<@data> using the expression inside the block. Then it
selects and orders the C<$n> elements with the lower keys when
compared lexicographically.
It is equivalent to the pure Perl expression:
(sort { CALC_KEY($a) cmp CALC_KEY($b) } @data)[0 .. $n-1];
If $n is negative, the last C<$n> elements from the bottom are selected:
topsort 3 => qw(foo doom me bar doz hello);
# ==> ('bar', 'doz', 'doom')
topsort -3 => qw(foo doom me bar doz hello);
# ==> ('foo', 'hello', 'me')
top 3 => qw(foo doom me bar doz hello);
# ==> ('doom', 'bar', 'doz')
top -3 => qw(foo doom me bar doz hello);
# ==> ('foo', 'me', 'hello')
In scalar context, the value returned by the functions on this module
is the cutoff value allowing to select nth element from the
array. For instance:
# n = 5;
scalar(topsort 5 => @data) eq (sort @data)[4] # true
# n = -5;
scalar(topsort -5 => @data) eq (sort @data)[-5] # true
Note that on scalar context, the C<sort> variations (see below) are
usually the right choice:
scalar topsort 3 => qw(me foo doz doom me bar hello); # ==> 'doz'
scalar top 3 => qw(me foo doz doom me bar hello); # ==> 'bar'
Note also, that the index is 1-based (it starts at one instead of at
zero). The C<atpos> set of functions explained below do the same and
are 0-based.
Variations allow to:
=over 4
=item - use the own values as the ordering keys
topsort 5 => qw(a b ab t uu g h aa aac);
# ==> a aa aac ab b
=item - use an array or hash index instead of a subroutine to extract
the key
slottop 0, 2, [4], [1], [3], [2], [4];
# ==> [1], [2]
=item - return the selected values in the original order
top 5 => qw(a b ab t uu g h aa aac);
# ==> a b ab aa aac
=item - use a different ordering
For instance comparing the keys as numbers, using the locale
configuration or in reverse order:
rnkeytop { length $_ } 3 => qw(a ab aa aac b t uu g h);
# ==> ab aa aac
rnkeytopsort { length $_ } 3 => qw(a ab aa aac b t uu g h);
# ==> aac ab aa
A prefix is used to indicate the required ordering:
=over 4
=item (no prefix)
lexicographical ascending order
=item r
lexicographical descending order
=item l
lexicographical ascending order obeying locale configuration
=item r
lexicographical descending order obeying locale configuration
=item n
numerical ascending order
=item rn
numerical descending order
=item i
numerical ascending order but converting the keys to integers first
=item ri
numerical descending order but converting the keys to integers first
=item u
numerical ascending order but converting the keys to unsigned integers first
=item ru
numerical descending order but converting the keys to unsigned integers first
=back
=item - select the head element from the list sorted
nhead 6, 7, 3, 8, 9, 9;
# ==> 3
nkeyhead { length $_ } qw(a ab aa aac b t uu uiyii)
# ==> 'a'
=item - select the tail element from the list sorted
tail qw(a ab aa aac b t uu uiyii);
# ==> 'uu'
nkeytail { length $_ } qw(a ab aa aac b t uu uiyii)
# ==> 'uiyii'
=item - select the element at position n from the list sorted
atpos 3, qw(a ab aa aac b t uu uiyii);
# ==> 'ab';
rnkeyatpos { abs $_ } 2 => -0.3, 1.1, 4, 0.1, 0.9, -2;
# ==> 1.1
rnkeyatpos { abs $_ } -2 => -0.3, 1.1, 4, 0.1, 0.9, -2;
# ==> -0.3
Note that for the C<atpos> set of functions indexes start at zero.
=item - return a list composed by the elements with the first n
ordered keys and then the remaining ones.
ikeypart { length $_ } 3 => qw(a bbbb cc ddddd g fd);
# ==> a cc g bbbb ddddd fd
=item - return two arrays references, the first array containing the
elements with the first n ordered keys and the second with the rest.
keypartref { length $_ } 3 => qw(a bbbb cc ddddd g fd);
# ==> [a cc g] [bbbb ddddd fd]
=back
The full list of available functions is:
top ltop ntop itop utop rtop rltop rntop ritop rutop
keytop lkeytop nkeytop ikeytop ukeytop rkeytop rlkeytop rnkeytop
rikeytop rukeytop
slottop lslottop nslottop islottop uslottop rslottop rlslottop rnslottop
rislottop ruslottop
topsort ltopsort ntopsort itopsort utopsort rtopsort rltopsort
rntopsort ritopsort rutopsort
keytopsort lkeytopsort nkeytopsort ikeytopsort ukeytopsort
rkeytopsort rlkeytopsort rnkeytopsort rikeytopsort rukeytopsort
slottopsort lslottopsort nslottopsort islottopsort uslottopsort
rslottopsort rlslottopsort rnslottopsort rislottopsort ruslottopsort
head lhead nhead ihead uhead rhead rlhead rnhead rihead ruhead
keyhead lkeyhead nkeyhead ikeyhead ukeyhead rkeyhead rlkeyhead
rnkeyhead rikeyhead rukeyhead
slothead lslothead nslothead islothead uslothead rslothead rlslothead
rnslothead rislothead ruslothead
tail ltail ntail itail utail rtail rltail rntail ritail rutail
keytail lkeytail nkeytail ikeytail ukeytail rkeytail rlkeytail
rnkeytail rikeytail rukeytail
slottail lslottail nslottail islottail uslottail rslottail rlslottail
rnslottail rislottail ruslottail
atpos latpos natpos iatpos uatpos ratpos rlatpos rnatpos riatpos
ruatpos
keyatpos lkeyatpos nkeyatpos ikeyatpos ukeyatpos rkeyatpos
rlkeyatpos rnkeyatpos rikeyatpos rukeyatpos
slotatpos lslotatpos nslotatpos islotatpos uslotatpos rslotatpos
rlslotatpos rnslotatpos rislotatpos ruslotatpos
part lpart npart ipart upart rpart rlpart rnpart ripart
rupart
keypart lkeypart nkeypart ikeypart ukeypart rkeypart
rlkeypart rnkeypart rikeypart rukeypart
slotpart lslotpart nslotpart islotpart uslotpart rslotpart
rlslotpart rnslotpart rislotpart ruslotpart
=head1 SEE ALSO
L<Sort::Key>, L<perlfunc/sort>.
L<Sort::Key::Top::PP> by Toby Inkster, provides a subset of the API of
Sort::Key::Top and is written in pure Perl.
The Wikipedia article about selection algorithms
L<http://en.wikipedia.org/wiki/Selection_algorithm>.
=head1 COPYRIGHT AND LICENSE
Copyright (C) 2006-2008, 2011, 2012, 2014 by Salvador FandiE<ntilde>o
(sfandino@yahoo.com).
This library is free software; you can redistribute it and/or modify
it under the same terms as Perl itself, either Perl version 5.8.8 or,
at your option, any later version of Perl 5 you may have available.
=cut