#!/usr/bin/pugs
use v6;

class MultiCounter {
      has @.positions is rw;
      has @.lengths   is rw;
      submethod BUILD() { @.positions = (0) xx (@.lengths.end + 1); }
      method inc () returns Bool {
        @.positions[-1]++;
        for reverse (0..@.lengths.end - 1) -> $i {
         if (@.positions[$i + 1] > @.lengths[$i + 1]) {
            @.positions[$i]++;
            @.positions[$i + 1] = 0;
         }
        }
        
        return (@.positions[0] > @.lengths[0]) ?? 0 :: 1;             
      }                
}

class NestedLoops {
      has @.loops is rw;
      has MultiCounter $.counter is r;
      submethod BUILD() {
          $.counter = MultiCounter.new( :lengths( @.loops.map:{.end } ) );
      }
      method inc () returns Bool { $.counter.inc;  }
      method data () {
          my @data;
          for (0..@.loops.end) -> $i {
              push @data, @.loops[ $i ][$.counter.positions[$i]];
          }
          return @data;
      };
}

my $counter = NestedLoops.new( :loops(['a','b'],[0..2], ['one',2,3]) );
while ($counter.inc) {
    $counter.data.join(" ").say;
}