List::Util - A selection of general-utility list subroutines
use List::Util qw(sum min max minstr maxstr reduce);
List::Util contains a selection of subroutines that people have expressed would be nice to have in the perl core, but the usage would not really be high enough to warrant the use of a keyword, and the size so small such that being individual extensions would be wasteful.
List::Util
By default List::Util does not export any subroutines. The subroutines defined are
Returns the entry in the list with the highest numerical value. If the list is empty then undef is returned.
undef
$foo = max 1..10 # 10 $foo = max 3,9,12 # 12 $foo = max @bar, @baz # whatever
This function could be implemented using reduce like this
reduce
$foo = reduce { $a > $b ? $a : $b } 1..10
Similar to max, but treats all the entries in the list as strings and returns the highest string as defined by the gt operator. If the list is empty then undef is returned.
max
gt
$foo = maxstr 'A'..'Z' # 'Z' $foo = maxstr "hello","world" # "world" $foo = maxstr @bar, @baz # whatever
$foo = reduce { $a gt $b ? $a : $b } 'A'..'Z'
Similar to max but returns the entry in the list with the lowest numerical value. If the list is empty then undef is returned.
$foo = min 1..10 # 1 $foo = min 3,9,12 # 3 $foo = min @bar, @baz # whatever
$foo = reduce { $a < $b ? $a : $b } 1..10
Similar to min, but treats all the entries in the list as strings and returns the lowest string as defined by the lt operator. If the list is empty then undef is returned.
min
lt
$foo = maxstr 'A'..'Z' # 'A' $foo = maxstr "hello","world" # "hello" $foo = maxstr @bar, @baz # whatever
$foo = reduce { $a lt $b ? $a : $b } 'A'..'Z'
Reduces LIST by calling BLOCK, or the sub referenced by SUBREF, multiple times with two arguments. The first call will be with the first two elements of the list, subsequent calls will be done by passing the result of the previous call and the next element in the list.
Returns the result of the last call to BLOCK. If LIST is empty then undef is returned. If LIST only contains one element then that element is returned and BLOCK is not executed.
$foo = reduce { $a < $b ? $a : $b } 1..10 # min $foo = reduce { $a lt $b ? $a : $b } 'aa'..'zz' # minstr $foo = reduce { $a + $b } 1 .. 10 # sum $foo = reduce { $a . $b } @bar # concat
Returns the sum of all the elements in LIST.
$foo = sum 1..10 # 55 $foo = sum 3,9,12 # 24 $foo = sum @bar, @baz # whatever
$foo = reduce { $a + $b } 1..10
It should be noted that this module is not intended to be a bit bucket for any sub that some person thinks might be useful. Some general guidelines are to consider if a particular sub should be included in List::Util are
The sub is of general use and cannot be implemented in perl.
or
The sub is very commonly used and needs fast implementation in C.
Copyright (c) 1997-1999 Graham Barr <gbarr@pobox.com>. All rights reserved. This program is free software; you can redistribute it and/or modify it under the same terms as Perl itself.
To install Ref::Util, copy and paste the appropriate command in to your terminal.
cpanm
cpanm Ref::Util
CPAN shell
perl -MCPAN -e shell install Ref::Util
For more information on module installation, please visit the detailed CPAN module installation guide.