> But, as Luke pointed out, some of the other syntax required to make
> that work is isn't particularly friendly:
>
> coro pre_traverse(%data) {
> yield %data{ value };
> yield $_ for <&_.clone(%data{ left })>;
> yield $_ for <&_.clone(%data{ right })>;
> }
>
> If I work backwards, the syntax I'd _want_ for something like that
> would be much like Luke proposed:
>
> sub pre_traverse(%data) is coroutine {
> yield %data{ value };
> pre_traverse( %data{ left } );
> pre_traverse( %data{ right } );
> }
>
> ... where the internal pre_traverses are yielding the _original_
> pre_traverse. Whoa, though, that doesn't really work, because you'd
> have to implicitly do the clone, which screws up the normal iterator
> case! And I don't immediately know how to have a syntax do the right
> thing in _both_ cases.
>
> So, if I have to choose between the two, I think I'd rather iteration
> be easy than recursion be easy. If lines like
>
> yield $_ for <&_.clone(%data{ left })>;
>
> are too scary, we might be able to make a keyword that does that, like:
>
> sub pre_traverse(%data) is coroutine {
> yield %data{ value };
> delegate pre_traverse( %data{ left } );
> delegate pre_traverse( %data{ right } );
> }
>
> Maybe. But in truth, that seems no more intuitive than the first.
Well, at least it's not using all those fancy features that will scare
off non-gurus. But I think that instead of something declared coro
I<returning> a coroutine iterator, why not just make it one (which I
believe was Damian's original intent)?
for <&foo> {...}
A subroutine could gladly return one of these iterators in place of a
different kind of iterator (or iterable structure).
The problems come when passing arguments to it. For that, you can use
a coroutine factory, or you can do it this way:
for < coro { foo($a, $b) } > {...}
We might need some shorthand for that... but probably not.
This is interesting:
my $coro = coro { foo($a, $b) };
$coro();
Calls foo($a, $b) without becoming a coroutine. I don't know whether
this is useful or just strangely counter-intuitive.
Luke
