A modest counter-proposal to this idea:
What if we just stopped requiring commas in import/export lists? As far as I can tell, they're not necessary for proper parsing.
This doesn't solve other problems, but I'm not convinced every problem in this domain needs the same solution.
In particular, I'm -1 on allowing a loose interpretation of commas in lists, as it seems very strange to have commas in lists and commas in tuples have a different meaning. (I'm +1 on fixing import/export lists, though.)
Richard
On Sep 25, 2014, at 8:06 AM, Herbert Valerio Riedel
On 2014-09-25 at 13:34:16 +0200, Daniel Trstenjak wrote:
[...]
One compromise could be, that additional commatas in literal lists are only allowed at the beginning and at the end.
...another idea could be to make it a separate Pragma (e.g. ExtraCommasLists) if there's a chance of ListSections (which would conflict with this) becoming a reality.
Then your use case would work and also something like:
abc = [ -- a , a -- b , b -- c , c ]
I'd probably prefer leading-comma over trailing-comma style anyway (as I've grown to like it over the years).
I think that are the main uses of additional commatas in literal lists and I can't see that someone really wants a list literal like '[,3,,4,]', so wrongly reading it as a list section shouldn't be an issue.
Yeah, I don't care much about extra middle-commas either. Personally, I'd be already happy with just trailing & leading extra-comma support. _______________________________________________ ghc-devs mailing list ghc-devs@haskell.org http://www.haskell.org/mailman/listinfo/ghc-devs