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Sort::Key.3pm

NAME

Sort::Key - the fastest way to sort anything in Perl

SYNOPSIS

   use Sort::Key qw(keysort nkeysort ikeysort);
 
   @by_name = keysort { "$_->{surname} $_->{name}" } @people;
 
   # sorting by a numeric key:
   @by_age = nkeysort { $_->{age} } @people;
 
   # sorting by a numeric integer key:
   @by_sons = ikeysort { $_->{sons} } @people;
 
 

DESCRIPTION

Sort::Key provides a set of functions to sort lists of values by some calculated key value.

It is faster (usually much faster) and uses less memory than other alternatives implemented around perl sort function (ST, GRT, etc.).

Multikey sorting functionality is also provided via the companion modules Sort::Key::Multi, Sort::Key::Maker and Sort::Key::Register.

FUNCTIONS

This module provides a large number of sorting subroutines but they are all variations off the "keysort" one:

   @sorted = keysort { CALC_KEY($_) } @data
 
 

that is conceptually equivalent to

   @sorted = sort { CALC_KEY($a) cmp CALC_KEY($b) } @data
 
 

and where "CALC_KEY($_)" can be any expresion to extract the key value from $_ (not only a subroutine call).

For instance, some variations are "nkeysort" that performs a numeric comparison, "rkeysort" that orders the data in descending order, "ikeysort" and "ukeysort" that are optimized versions of "nkeysort" that can be used when the keys are integers or unsigned integers respectively, etc.

Also, inplace versions of the sorters are provided. For instance

   keysort_inplace { CALC_KEY($_) } @data
 
 

that is equivalent to

   @data = keysort { CALC_KEY($_) } @data
 
 

but being (a bit) faster and using less memory.

The full list of subroutines that can be imported from this module follows:

keysort { CALC_KEY } @array

returns the elements on @array sorted by the key calculated applying "{ CALC_KEY }" to them.

Inside "{ CALC_KEY }", the object is available as $_.

For example:

   @a=({name=>john, surname=>smith}, {name=>paul, surname=>belvedere});
   @by_name=keysort {$_->{name}} @a;
 
 

This function honours the "use locale" pragma.

nkeysort { CALC_KEY } @array

similar to keysort but compares the keys numerically instead of as strings.

This function honours the "use integer" pragma, i.e.:

   use integer;
   my @s=(2.4, 2.0, 1.6, 1.2, 0.8);
   my @ns = nkeysort { $_ } @s;
   print "@ns\n"
 
 

prints

   0.8 1.6 1.2 2.4 2
 
 

rnkeysort { CALC_KEY } @array

works as nkeysort, comparing keys in reverse (or descending) numerical order.

ikeysort { CALC_KEY } @array

works as keysort but compares the keys as integers (32 bits or more, no checking is performed for overflows).

rikeysort { CALC_KEY } @array

works as ikeysort, but in reverse (or descending) order.

ukeysort { CALC_KEY } @array

works as keysort but compares the keys as unsigned integers (32 bits or more).

For instance, it can be used to efficiently sort IP4 addresses:

   my @data = qw(1.2.3.4 4.3.2.1 11.1.111.1 222.12.1.34
                 0.0.0.0 255.255.255.0) 127.0.0.1);
 
   my @sorted = ukeysort {
                    my @a = split /\./;
                    (((($a[0] << 8) + $a[1] << 8) + $a[2] << 8) + $a[3])
                } @data;
 
 

rukeysort { CALC_KEY } @array

works as ukeysort, but in reverse (or descending) order.

keysort_inplace { CALC_KEY } @array

nkeysort_inplace { CALC_KEY } @array

ikeysort_inplace { CALC_KEY } @array

ukeysort_inplace { CALC_KEY } @array

rkeysort_inplace { CALC_KEY } @array

rnkeysort_inplace { CALC_KEY } @array

rikeysort_inplace { CALC_KEY } @array

rukeysort_inplace { CALC_KEY } @array

work as the corresponding keysort functions but sorting the array inplace.

rsort @array

nsort @array

rnsort @array

isort @array

risort @array

usort @array

rusort @array

rsort_inplace @array

nsort_inplace @array

rnsort_inplace @array

isort_inplace @array

risort_inplace @array

usort_inplace @array

rusort_inplace @array

are simplified versions of its keysort cousins. They use the own values as the sorting keys.

For instance those constructions are equivalent:

   @sorted = nsort @foo;
 
   @sorted = nkeysort { $_ } @foo;
 
   @sorted = sort { $a <=> $b } @foo;
 
 

multikeysorter(@types)

multikeysorter_inplace(@types)

multikeysorter(\&genkeys, @types)

multikeysorter_inplace(\&genkeys, @types)

are the low level interface to the multikey sorting functionality (normally, you should use Sort::Key::Maker and Sort::Key::Register or Sort::Key::Multi instead).

They get a list of keys descriptions and return a reference to a multikey sorting subroutine.

Types accepted by default are:

   string, str, locale, loc, integer, int,
   unsigned_integer, uint, number, num
 
 

and support for additional types can be added via the non exportable register_type subroutine (see below) or the more friendly interface available from Sort::Key::Register.

Types can be preceded by a minus sign to indicate descending order.

If the first argument is a reference to a subroutine it is used as the multikey extraction function. If not, the generated sorters expect one as their first argument.

Example:

   my $sorter1 = multikeysorter(sub {length $_, $_}, qw(int str));
   my @sorted1 = &$sorter1(qw(foo fo o of oof));
 
   my $sorter2 = multikeysorter(qw(int str));
   my @sorted2 = &$sorter2(sub {length $_, $_}, qw(foo fo o of oof));
 
 

Sort::Key::register_type($name, \&gensubkeys, @subkeystypes)

registers a new datatype named $name defining how to convert it to a multikey.

&gensubkeys should convert the object of type $name passed on $_ to a list of values composing the multikey.

@subkeystypes is the list of types for the generated multikeys.

For instance:

   Sort::Key::register_type Person =>
                  sub { $_->surname,
                        $_->name,
                        $_->middlename },
                  qw(str str str);
 
   Sort::Key::register_type Color =>
                  sub { $_->R, $_->G, $_->B },
                  qw(int int int);
 
 

Once a datatype has been registered it can be used in the same way as types supported natively, even for defining new types, i.e.:

   Sort::Key::register_type Family =>
                  sub { $_->man, $_->woman },
                  qw(Person Person);
 
 

SEE ALSO

perl sort function, integer, locale.

Companion modules Sort::Key::Multi, Sort::Key::Register, Sort::Key::Maker and Sort::Key::Natural.

Other interesting Perl sorting modules are Sort::Maker and Sort::Natural.

COPYRIGHT AND LICENSE

Copyright (C) 2005, 2006 by Salvador Fandin~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 5.8.4 or, at your option, any later version of Perl 5 you may have available.