Re: plaintive whine about 'for' syntax

[Chris Dutton]

On Thursday, October 31, 2002, at 10:03  PM, John Siracusa wrote:

On 10/31/02 5:33 PM, [EMAIL PROTECTED] wrote:

Damian Conway writes:

BTW, Both Larry and I do understand the appeal of interleaving
sources and iterators. We did consider it at some length back
in January, when we spent a week thrashing this syntax out.

Of course, I can't speak for Larry, but in the end I concluded
that interleaving iterator variables is a false win, since it
trades reduced syntactic complexity for increased semantic
complexity, but only really improves the readability of a
comparatively rare case.

but why ? I am just curious about details.

Yeah, I'd like to hear those details too, because the alternate syntax:

1) for  @a -> $x ; @b -> $y   { ... }

sure looks a lot more attractive and sensible to me, and I agree with all
the arguments in favor of it so far. In particular:

* No "look here, then look there" connection between (possibly) widely
separated items.

* Simple to add or remove/comment-out individual stream/item(s) pairs
without having to "count" what are essentially positional parameters to make
sure you haven't mis-mapped anything in the process.

* More familiar use of the semicolon (IMO)

The current syntax offers a significant advantage, though. I'm assuming parser knows to look for equal numbers of things on both sides of the ->. If we go with the proposed alternate syntax, won't we run into the problem where it sees:

for @a -> $a; as a complete postfix for loop that just happens to do nothing?

I suppose the same could be said for the existing syntax. "for @a;" would look like a loop with the default topic variable. Maybe I'm just wrong, but the proposed syntax seems to introduce ambiguity by breaking the for loop up a bit too much, while the current use of the "->" and semicolons holds the whole thing together.

As for maintaining the sanctity of the semicolon, I would offer that consistency of the arrow operator is more important.