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authorSiep Kroonenberg <siepo@cybercomm.nl>2011-02-17 17:57:31 +0000
committerSiep Kroonenberg <siepo@cybercomm.nl>2011-02-17 17:57:31 +0000
commit320d8694fec25ed148613684543b5a0504a046ae (patch)
tree0ddcf933d3acd3c98a387fa2bf73d0554ca6e50d /Master/tlpkg/tlperl/lib/List/Util.pm
parent779e71f16ca01a6244b632b95bdb461fec163b34 (diff)
New tlperl part XIV
git-svn-id: svn://tug.org/texlive/trunk@21436 c570f23f-e606-0410-a88d-b1316a301751
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+# List::Util.pm
+#
+# Copyright (c) 1997-2009 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.
+#
+# This module is normally only loaded if the XS module is not available
+
+package List::Util;
+
+use strict;
+use vars qw(@ISA @EXPORT_OK $VERSION $XS_VERSION $TESTING_PERL_ONLY);
+require Exporter;
+
+@ISA = qw(Exporter);
+@EXPORT_OK = qw(first min max minstr maxstr reduce sum shuffle);
+$VERSION = "1.22";
+$XS_VERSION = $VERSION;
+$VERSION = eval $VERSION;
+
+eval {
+ # PERL_DL_NONLAZY must be false, or any errors in loading will just
+ # cause the perl code to be tested
+ local $ENV{PERL_DL_NONLAZY} = 0 if $ENV{PERL_DL_NONLAZY};
+ eval {
+ require XSLoader;
+ XSLoader::load('List::Util', $XS_VERSION);
+ 1;
+ } or do {
+ require DynaLoader;
+ local @ISA = qw(DynaLoader);
+ bootstrap List::Util $XS_VERSION;
+ };
+} unless $TESTING_PERL_ONLY;
+
+
+if (!defined &sum) {
+ require List::Util::PP;
+ List::Util::PP->import;
+}
+
+1;
+
+__END__
+
+=head1 NAME
+
+List::Util - A selection of general-utility list subroutines
+
+=head1 SYNOPSIS
+
+ use List::Util qw(first max maxstr min minstr reduce shuffle sum);
+
+=head1 DESCRIPTION
+
+C<List::Util> contains a selection of subroutines that people have
+expressed would be nice to have in the perl core, but the usage would
+not really be high enough to warrant the use of a keyword, and the size
+so small such that being individual extensions would be wasteful.
+
+By default C<List::Util> does not export any subroutines. The
+subroutines defined are
+
+=over 4
+
+=item first BLOCK LIST
+
+Similar to C<grep> in that it evaluates BLOCK setting C<$_> to each element
+of LIST in turn. C<first> returns the first element where the result from
+BLOCK is a true value. If BLOCK never returns true or LIST was empty then
+C<undef> is returned.
+
+ $foo = first { defined($_) } @list # first defined value in @list
+ $foo = first { $_ > $value } @list # first value in @list which
+ # is greater than $value
+
+This function could be implemented using C<reduce> like this
+
+ $foo = reduce { defined($a) ? $a : wanted($b) ? $b : undef } undef, @list
+
+for example wanted() could be defined() which would return the first
+defined value in @list
+
+=item max LIST
+
+Returns the entry in the list with the highest numerical value. If the
+list is empty then C<undef> is returned.
+
+ $foo = max 1..10 # 10
+ $foo = max 3,9,12 # 12
+ $foo = max @bar, @baz # whatever
+
+This function could be implemented using C<reduce> like this
+
+ $foo = reduce { $a > $b ? $a : $b } 1..10
+
+=item maxstr LIST
+
+Similar to C<max>, but treats all the entries in the list as strings
+and returns the highest string as defined by the C<gt> operator.
+If the list is empty then C<undef> is returned.
+
+ $foo = maxstr 'A'..'Z' # 'Z'
+ $foo = maxstr "hello","world" # "world"
+ $foo = maxstr @bar, @baz # whatever
+
+This function could be implemented using C<reduce> like this
+
+ $foo = reduce { $a gt $b ? $a : $b } 'A'..'Z'
+
+=item min LIST
+
+Similar to C<max> but returns the entry in the list with the lowest
+numerical value. If the list is empty then C<undef> is returned.
+
+ $foo = min 1..10 # 1
+ $foo = min 3,9,12 # 3
+ $foo = min @bar, @baz # whatever
+
+This function could be implemented using C<reduce> like this
+
+ $foo = reduce { $a < $b ? $a : $b } 1..10
+
+=item minstr LIST
+
+Similar to C<min>, but treats all the entries in the list as strings
+and returns the lowest string as defined by the C<lt> operator.
+If the list is empty then C<undef> is returned.
+
+ $foo = minstr 'A'..'Z' # 'A'
+ $foo = minstr "hello","world" # "hello"
+ $foo = minstr @bar, @baz # whatever
+
+This function could be implemented using C<reduce> like this
+
+ $foo = reduce { $a lt $b ? $a : $b } 'A'..'Z'
+
+=item reduce BLOCK LIST
+
+Reduces LIST by calling BLOCK, in a scalar context, multiple times,
+setting C<$a> and C<$b> each time. The first call will be with C<$a>
+and C<$b> set to the first two elements of the list, subsequent
+calls will be done by setting C<$a> to the result of the previous
+call and C<$b> to the next element in the list.
+
+Returns the result of the last call to BLOCK. If LIST is empty then
+C<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
+
+If your algorithm requires that C<reduce> produce an identity value, then
+make sure that you always pass that identity value as the first argument to prevent
+C<undef> being returned
+
+ $foo = reduce { $a + $b } 0, @values; # sum with 0 identity value
+
+=item shuffle LIST
+
+Returns the elements of LIST in a random order
+
+ @cards = shuffle 0..51 # 0..51 in a random order
+
+=item sum LIST
+
+Returns the sum of all the elements in LIST. If LIST is empty then
+C<undef> is returned.
+
+ $foo = sum 1..10 # 55
+ $foo = sum 3,9,12 # 24
+ $foo = sum @bar, @baz # whatever
+
+This function could be implemented using C<reduce> like this
+
+ $foo = reduce { $a + $b } 1..10
+
+If your algorithm requires that C<sum> produce an identity of 0, then
+make sure that you always pass C<0> as the first argument to prevent
+C<undef> being returned
+
+ $foo = sum 0, @values;
+
+=back
+
+=head1 KNOWN BUGS
+
+With perl versions prior to 5.005 there are some cases where reduce
+will return an incorrect result. This will show up as test 7 of
+reduce.t failing.
+
+=head1 SUGGESTED ADDITIONS
+
+The following are additions that have been requested, but I have been reluctant
+to add due to them being very simple to implement in perl
+
+ # One argument is true
+
+ sub any { $_ && return 1 for @_; 0 }
+
+ # All arguments are true
+
+ sub all { $_ || return 0 for @_; 1 }
+
+ # All arguments are false
+
+ sub none { $_ && return 0 for @_; 1 }
+
+ # One argument is false
+
+ sub notall { $_ || return 1 for @_; 0 }
+
+ # How many elements are true
+
+ sub true { scalar grep { $_ } @_ }
+
+ # How many elements are false
+
+ sub false { scalar grep { !$_ } @_ }
+
+=head1 SEE ALSO
+
+L<Scalar::Util>, L<List::MoreUtils>
+
+=head1 COPYRIGHT
+
+Copyright (c) 1997-2007 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.
+
+=cut