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.).

       Multi-key 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 expression 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 multi-key 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 multi-key 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 register_type subroutine available from
           Sort::Key::Types 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 multi-key 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));

SEE ALSO

       perl sort function, integer, locale.

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

       Sort::Key::IPv4, Sort::Key::DateTime and Sort::Key::OID modules add support for additional datatypes to
       Sort::Key.

       Sort::Key::External allows one to sort huge lists that do not fit in the available memory.

       Other interesting Perl sorting modules are Sort::Maker, Sort::Naturally and Sort::External.

SUPPORT

       To report bugs, send me and email or use the CPAN bug tracking system at <http://rt.cpan.org>.

   Commercial support
       Commercial support, professional services and custom software development around this module are
       available through my current company. Drop me an email with a rough description of your requirements and
       we will get back to you ASAP.

   My wishlist
       If you like this module and you're feeling generous, take a look at my Amazon Wish List:
       <http://amzn.com/w/1WU1P6IR5QZ42>

COPYRIGHT AND LICENSE

       Copyright (C) 2005-2007, 2012, 2014 by Salvador Fandiño, <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.