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tye,
I expanded the code I came up with for combinations of a fixed size:
```#!/usr/bin/perl
use strict;
use warnings;

my \$iter = combo( 30..50 );
while ( my @combo = \$iter->() ) {
print "@combo\n";
}

sub combo {
my @list = @_;
return sub { () } if ! @_;

my (@position, @stop, \$end_pos, \$done);
my (\$by, \$next) = (0, 1);

return sub {
return () if \$done;
if ( \$next ) {
\$by++;
return () if \$by > @list;
@position = (0 .. \$by - 2, \$by - 2);
@stop     = @list - \$by .. \$#list;
\$end_pos  = \$#position;
\$next = undef;
}
my \$cur = \$end_pos;
{
if ( ++\$position[ \$cur ] > \$stop[ \$cur ] ) {
\$position[ --\$cur ]++;
redo if \$position[ \$cur ] > \$stop[ \$cur ];
my \$new_pos = \$position[ \$cur ];
@position[ \$cur .. \$end_pos ] = \$new_pos .. \$new_pos +
+ \$by;
}
}
if ( \$position[0] == \$stop[0] ) {
\$position[0] == @list ? \$done = 1 : \$next = 1;
}
return @list[ @position ];
}
}
I haven't analyzed its O factor or spent a lot of time with good benchmarks, but it does appear to be considerably faster for combinations of 30..50.

Cheers - L~R

In reply to Re^2: Finding all Combinations by Limbic~Region
in thread Finding all Combinations by narse

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