comment on

blokhead,
I doubt this is how tye would have implemented it, but this is 1 implementation of his 3 simple rules:

#!/usr/bin/perl
use strict;
use warnings;

my $next = iter_powerset( 1,2,3,4,5 );
while ( my @combo = $next->() ) {
    print "@combo\n";
}

sub iter_powerset {
    my @factor = @_;
    my $end = $#factor;
    my @subset = (undef) x $end;
    my ($pos, $mode) = (-1, 1);
    my $return = sub { return @factor[ grep defined, @subset ] };
    my %dispatch = (
        1 => sub {
            ++$pos;
            $subset[ $pos ] = $pos;
            ++$mode if $pos == $end;
            $return->();
        },
        2 => sub {
            $subset[ $pos - 1 ] = undef;
            ++$mode;
            $return->();
        },
        3 => sub {
            $subset[ $pos-- ] = undef;
            while ( $pos >= 0 ) {
                last if defined $subset[ $pos ];
                --$pos;
            }
            $subset[ $pos++ ] = undef;
            return () if ! $pos;
            $subset[ $pos ] = $pos;
            $mode = 1;
            $return->();
        },
    );
    return sub { $dispatch{ $mode }->() };
}
[download]

I am now going to play with making it closer to what I want for the other task.

Cheers - L~R

Since tye's 3 simple rules were uttered in passing on the CB, I will summarize them here to help explain the code

Mode 1: Fill to the right until you reach the end
Mode 2: Remove second to last element
Mode 3: Remove last element, increment new last element

In reply to Re^2: Generating powerset with progressive ordering by Limbic~Region
in thread Generating powerset with progressive ordering by Limbic~Region

Are you posting in the right place? Check out Where do I post X? to know for sure.
Posts may use any of the Perl Monks Approved HTML tags. Currently these include the following:
<code> <a> <b> <big> <blockquote> <br /> <dd> <dl> <dt> <em> <font> <h1> <h2> <h3> <h4> <h5> <h6> <hr /> <i> <li> <nbsp> <ol> <p> <small> <strike> <strong> <sub> <sup> <table> <td> <th> <tr> <tt> <u> <ul>
Snippets of code should be wrapped in <code> tags not <pre> tags. In fact, <pre> tags should generally be avoided. If they must be used, extreme care should be taken to ensure that their contents do not have long lines (<70 chars), in order to prevent horizontal scrolling (and possible janitor intervention).
Want more info? How to link or How to display code and escape characters are good places to start.


Just another Perl shrine
	PerlMonks