proposal for trailing comma and semicolon

[Edward Kmett]

I personally use tuple sections a fair bit, though admittedly mostly for
simple (,a) or (a,) cases.


On Fri, May 17, 2013 at 3:01 PM, Ian Lynagh <ian at well-typed.com> wrote:

> 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/
>
>
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