Series Progress

After being stumped by it for a week, tonight I suddenly realized how to I could get the series operator working for the general cases. The trick was to keep an array storing the last N values generated in the series, where N is the number of arguments that the generator function takes. There was a good solid hour of banging my head against the compiler, but finally I got this:

> (1, 1, { $^a + $^b } ... *).batch(20).perl.say
(1, 1, 2, 3, 5, 8, 13, 21, 34, 55, 89, 144, 233, 377, 610, 987, 1597, 2584, 4181, 6765)

Here’s the key new code:

    my $arity = any( $next.signature.params>>.slurpy ) ?? Inf !! $next.count;

    gather {
        my @args;
        my $j;
        my $top = $arity min @lhs.elems;
        for 0..^$top -> $i {
            $j = @lhs[$i];
            take $j;
            @args.push($j);
        }

        if !$limit.defined || $limit cmp $j != 0 {
            loop {
                my $i = $next.(|@args);
                my $j = $i;
 
                my $cur_cmp = 1;
                if $limit.defined {
                    $cur_cmp = $limit cmp $j;
                    last if (@args[@args.elems - 1] cmp $limit) == $cur_cmp;
                }
                take $j;
                last if $cur_cmp == 0;

                @args.push($j);
                while @args.elems > $arity {
                    @args.shift;
                }
            }
        }
    }

I’m sure there are still some bugs hiding in there, and I need to throw a bunch more tests at it, but it seems like a fair evening’s work. I would love to get series test suggestions from people, and if you’d like to play with what I’ve got now, you can grab Rakudo’s “series” branch and build it locally.

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