Moving ArgumentsDo forward

Bardur Arantsson spam at
Wed Jun 1 15:09:37 UTC 2016

On 06/01/2016 01:48 PM, Akio Takano wrote:
> Hi,
> Ticket #10843 [0] proposes an extension, ArgumentsDo, which I would
> love to see in GHC. It's a small syntactic extension that allows do,
> case, if and lambda blocks as function arguments, without parentheses.
> However, its differential revision [1] has been abandoned, citing a
> mixed response from the community. A message [2] on the ticket
> summarizes a thread in haskell-cafe on this topic.
> I, for one, think adding this extension is worthwhile, because a
> significant number of people support it. Also, given how some people
> seem to feel ambivalent about this change, I believe actually allowing
> people to try it makes it clearer whether it is a good idea.
> Thus I'm wondering: is there any chance that this gets merged? If so,
> I'm willing to work on whatever is remaining to get the change merged.

What's changed since it was last discussed? I don't think the objections
were centered in the implementation, so I don't see what "whatever is
remaining to get the change merged" would be.

AFAICT at best it's a *very* small improvement[1] and fractures Haskell
syntax even more around extensions -- tooling etc. will need to
understand even *more* syntax extensions[2].


[1] If you grant that it is indeed an improvment, which I, personally,
don't think it is.

[2] I think most people agree that this is something that should perhaps
be handled by something like so that it would only need
to be implemented once, but there's not even an alpha release yet, so
that particular objection stands, AFAICT.

More information about the ghc-devs mailing list