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|
#! /usr/bin/perl -w
# This file is maintained at http://git.mdcc.cx/draai
# exec shuf : does the same, for input on stdin
# Copyright: © 2001 Joost van Baal
# This script is in the public domain.
use strict;
#
# permutate - give a random permutation
#
# permutate 3 e.g. could return (0, 2, 1)
#
sub permutate
{
my $n = shift;
my %h;
for my $i (0 .. $n-1) {
# rand $exp - a random fractional number >= 0, < $exp
my $r = int rand $n - $i;
my $k = -1;
# find r-th undefined key in %h
for my $j (0 .. $r) {
# go find the next undefined key after number $k
$k++;
while (defined $h{$k}) {
$k++;
}
}
# and fill it with $i
$h{$k} = $i;
}
return map { $h{$_} } (0 .. $n-1);
}
my @a;
if (@ARGV) {
@a = map { $ARGV[$_] } &permutate( scalar @ARGV );
print "@a\n";
} else {
@a = <>;
@a = map { $a[$_] } &permutate( scalar @a );
print @a;
}
__END__
=pod
=head1 NAME
dr_permutate - print randomly permutated arguments or stdin
=head1 SYNOPSIS
B<dr_permutate> I<arguments>
B<dr_permutate>
=head1 DESCRIPTION
When called with arguments, B<dr_permutate> returns its arguments in randomly
permutated order, space separated. When called without any arguments,
B<dr_permuate> expects a line-oriented file on stdin. It returns the contents of
this file, with lines randomly permutated.
=head1 EXAMPLE
Running
$ dr_permutate foo bar baz
could return
bar foo baz
. Running
$ cat <<EOF | dr_permutate
foo
bar
baz
could return
bar
foo
baz
.
=head1 HISTORY
This script was initially written on 2001-05-06.
=head1 BUGS
When called without any arguments, stdin is read in core entirely.
The GNU coreutils utility shuf(1) implements the same functionality in a
better way, you're probably better off using that.
=head1 SEE ALSO
http://packages.debian.org/randomize-lines
unsort(1), by Wessel Dankers.
=head1 COPYRIGHT
Copyright: (c) 2001 Joost van Baal
This script is in the public domain.
=head1 AUTHOR
Joost van Baal <joostvb@mdcc.cx>
=cut
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