Re^4: Perl6 Contest #2: P6 That Doesn't Look Like P5

[tall_man]

in reply to Re^3: Perl6 Contest #2: P6 That Doesn't Look Like P5
in thread Perl6 Contest #2: P6 That Doesn't Look Like P5

Roy, I tried your code on the documentation example:

my $N = 4;
my $depth = 3;
my $i2 = nested_for([   [ 0..$N ],
             ( sub { [$_+1..$N] } ) x ($depth-1),
         ]);
print "@args\n" while @args = $i2->();

There seems to be a problem when the range hits the top. The output is:

0 1 2
0 1 3
0 1 4
0 2 3
0 2 4
0 3 4
0 4
1 2 3
1 2 4
1 3 4
1 4
2 3 4
2 4
3 4
4

[Roy Johnson]

That makes sense: the range ends up being [5..4], which is a no-iteration loop. What do you think should be the output?

NB: my code does not run under 5.8.1 (on a Mac). I don't know why, and I can't get 5.8.6 to compile. Grrr. I hate it when my PC works better than my Mac.

Update: and to answer my own question, I looked at what NestedLoops does. Sensibly enough, it does no iterations when there's a no-iteration loop. You can get this behavior by making the last line of nest be return((@out and @in) ? (@out, @in) : ());