Permitting trailing commas for record syntax ADT declarations

[Johan Tibell]

Sounds good to me.

On Thu, Sep 25, 2014 at 11:18 AM, Simon Peyton Jones <simonpj at microsoft.com>
wrote:

>  There’s a danger of disappearing into a bikeshed here.  I think it’s
> clear that:
>
> ·         If we have it at all, ExtraCommas should be a {-# LANGUAGE
> ExtraCommas #-} extension, like any other.
>
> ·         ExtraCommas should leave tuples alone (always)
>
>
>
> Provided there is that LANGUAGE extension, I have no objection to having
> it in GHC if Alexander wants to implement it.  It has low impact, and some
> people like it a lot.  People who don’t like it don’t have to switch on the
> extension.
>
>
>
> It’s unclear whether extra commas in literal lists [a,,b,,] should behave
> like TupleSections or like ExtraCommas.  My instinct is the former, because
> the only difference is round vs square parens.    That would suggest
> continuing to make extra commas illegal in literal lists, for now anyway.
> That’s a conservative choice, which is usually the side to err on when it’s
> a toss-up.
>
>
>
> OK?
>
>
>
> Simon
>
>
>
>
>
>
>
> *From:* Iavor Diatchki [mailto:iavor.diatchki at gmail.com]
> *Sent:* 25 September 2014 08:14
> *To:* Alexander Berntsen
> *Cc:* Edward Kmett; Simon Peyton Jones; ghc-devs at haskell.org
> *Subject:* Re: Permitting trailing commas for record syntax ADT
> declarations
>
>
>
> Hello,
>
>
>
> My 2c: I don't think that supporting trailing commas is worth the
> additional complexity to the compiler and the language.
>
>
>
> I work with Haskell on a daily basis, and I honestly don't think that this
> is going to simplify my job in any way.  On the other hand, it seems like
> it it will make it more complex to write tools that process Haskell, and to
> explain the syntax of the language to beginners.
>
>
>
> -Iavor
>
>
>
>
>
>
>
> On Wed, Sep 24, 2014 at 12:38 PM, Alexander Berntsen <alexander at plaimi.net>
> wrote:
>
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> On 24/09/14 08:50, Edward Kmett wrote:
> > I'm personally of the "it should be a language extension like
> > everything else" mindset
> Yeah, I'm going the Pragma route.
>
> > If we limit it to record-like notions, and import/export lists,
> > then we don't have to deal with conflicts with TupleSections and
> > while it is inconsistent to have tuples behave differently, than
> > other comma-separated lists, I'd really rather retain tuple
> > sections, which I use somewhat heavily, than lose them to mindless
> > uniformity over how we handle comma-separated lists.
> I'm implementing it for things where I 100% subjectively feel it makes
> sense. This does *not* include tuples, for the reason you mention.
>
> When I get the time, I will make a Wiki page outlining what I'm changing
> and my motivation for doing it. We can then have a discussion about
> where to draw the line.
>
>
> I need to figure out a more elegant solution than tweaking the parser
> for each individual item. If someone knows their way around this code,
> please talk to me on IRC/SIP/XMPP/whatever. Just email me for contact
> info. I'll be busy today with a haskell workshop, but I plan on
> spending the rest of the week on this business.
> - --
> Alexander
> alexander at plaimi.net
> https://secure.plaimi.net/~alexander
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> =l/sh
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