Help needed: Restrictions of proc-notation with RebindableSyntax

[Jan Bracker]

Simon, Richard,

thank you for your answer! I don't have time to look into the GHC sources
right now, but I will set aside some time after the holidays and take a
close look at what the exact restrictions on proc-notation are and document
them.

Since you suggested a rewrite of GHC's handling of proc-syntax, are there
any opinions on integrating generalized arrows (Joseph 2014) in the
process? I think they would greatly improve arrows! I don't know if I have
the time to attempt this, but if I find the time I would give it a try. Why
wasn't this integrated while it was still actively developed?

Best,
Jan

[Joseph 2014] https://www2.eecs.berkeley.edu/Pubs/TechRpts/
2014/EECS-2014-130.pdf



2016-11-29 12:41 GMT+00:00 Simon Peyton Jones <simonpj at microsoft.com>:

> Jan,
>
>
>
> Type checking and desugaring for arrow syntax has received Absolutely No
> Love for several years.  I do not understand how it works very well, and I
> would not be at all surprised if it is broken in corner cases.
>
>
>
> It really needs someone to look at it carefully, document it better, and
> perhaps refactor it – esp by using a different data type rather than
> piggy-backing on HsExpr.
>
>
>
> In the light of that understanding, I think rebindable syntax will be
> easier.
>
>
>
> I don’t know if you are up for that, but it’s a rather un-tended part of
> GHC.
>
>
>
> Thanks
>
>
>
> Simon
>
>
>
> *From:* ghc-devs [mailto:ghc-devs-bounces at haskell.org] *On Behalf Of *Richard
> Eisenberg
> *Sent:* 28 November 2016 22:30
> *To:* Jan Bracker <jan.bracker at googlemail.com>
> *Cc:* ghc-devs at haskell.org
> *Subject:* Help needed: Restrictions of proc-notation with
> RebindableSyntax
>
>
>
> Jan’s question is a good one, but I don’t know enough about procs to be
> able to answer. I do know that the answer can be found by looking for uses
> of `tcSyntaxOp` in the TcArrows module.... but I just can’t translate it
> all to source Haskell, having roughly 0 understanding of this end of the
> language.
>
>
>
> Can anyone else help Jan here?
>
>
>
> Richard
>
>
>
> On Nov 23, 2016, at 4:34 AM, Jan Bracker via ghc-devs <
> ghc-devs at haskell.org> wrote:
>
>
>
> Hello,
>
>
>
> I want to use the proc-notation together with RebindableSyntax. So far
> what I am trying to do is working fine, but I would like to know what the
> exact restrictions on the supplied functions are. I am introducing
> additional indices and constraints on the operations. The documentation [1]
> says the details are in flux and that I should ask directly.
>
>
>
> Best,
>
> Jan
>
>
>
> [1] https://downloads.haskell.org/~ghc/latest/docs/html/
> users_guide/glasgow_exts.html#rebindable-syntax-and-the-
> implicit-prelude-import
> <https://na01.safelinks.protection.outlook.com/?url=https:%2F%2Fdownloads.haskell.org%2F~ghc%2Flatest%2Fdocs%2Fhtml%2Fusers_guide%2Fglasgow_exts.html%23rebindable-syntax-and-the-implicit-prelude-import&data=02%7C01%7Csimonpj%40microsoft.com%7C80e472cedf78463bd18408d417de1af5%7C72f988bf86f141af91ab2d7cd011db47%7C1%7C0%7C636159690104764444&sdata=ygqePSmgcPKnPmKDBfZplkyjG9BIDBO1L1MWHNpqw88%3D&reserved=0>
>
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