proposal for trailing comma and semicolon

[Ian Lynagh]

On Fri, May 17, 2013 at 02:04:44PM -0400, Edward Kmett wrote:
> My main concern is its a really weird corner case for the grammar to
> remember for tuple sections and it does have very weird grammar
> specification issues.

Tuple sections could look like
    (True, _)
rather than
    (True,)

Does anyone know how common tuple sections are, incidentally? They've
been around since GHC 6.12, so it would be interesting to know if people
are actually using them.

> I really have no objection to it for the other cases. It'd make export
> lists cleaner,

Actually, you are already allowed an extra trailing comma in import and
export lists.

> maybe a few other cases, but how often can you really say
> you can meaningfully comment out one field of a tuple have have the
> surrounding code make any sense?

It happens occasionally, especially when simplifying code while
debugging.

Commenting out list items is much more common, though.

I'd be in favour of allowing a trailing or leading comma anywhere that
comma is used as a separator. TupleSections would need to be changed or
removed, though.


Thanks
Ian
-- 
Ian Lynagh, Haskell Consultant
Well-Typed LLP, http://www.well-typed.com/