in reply to How to restrict partitions

use warnings;
use strict;
use Integer::Partition qw();

my $i = Integer::Partition->new(6);

while (my $p = $i->next) {
    print join( ' ', @$p ), $/ if (@$p == 2) and ($p->[0] != $p->[1]);
}

__END__

5 1
4 2

[download]

Replies are listed 'Best First'.
Re^2: How to restrict partitions
by crunch_this! (Acolyte) on Jan 18, 2014 at 03:16 UTC
    if (@$p == 2) and ($p->[0] != $p->[1]);

    Thx for the quick reply, that definitely did the trick but is there a more general way to do this? I'm just thinking of all the 'ands' I'd have to include. What if I want exactly, say, 5 summands?

[reply]
[d/l]
      UPDATE: This does not satisfy the clarified requirements in the response. 

      use warnings;
use strict;
use Integer::Partition qw();

my $i = Integer::Partition->new(6);

while (my $p = $i->next()) {
    print join( ' ', @$p ), $/ if (@$p == 5) and not all_same(@$p);
}

sub all_same {
    my $same = 1;
    for (@_[1 .. $#_]) {
        if ($_ != $_[0]) {
            $same = 0;
            last;
        }
    }
    return $same;
}

__END__

2 1 1 1 1

      [download]
[reply]
[d/l]

        Or, if all the values of the partitions must be unique, maybe something like (untested): 

        use Integer::Partition qw();
use List::MoreUtils qw(uniq);

my $i = Integer::Partition->new(6);

my $n = 5;

while (my $p = $i->next()) {
    do_whatever_with($p) if (@$p == $n) and (@$p == uniq @$p);
    }

        [download]
[reply]
[d/l]
        That works to give me the exact number of summands I'm looking for but it give me repeat summands. I get the idea behind the subroutine but I'm not sure how to change it so that it gives only partitions with distinct summands. I tried tinkering with the truth values & the != etc but it didn't seem to do the trick.
[reply]

In Section Seekers of Perl Wisdom