[ghc-steering-committee] Amend or patterns (#522) to use p1 ; p2 (#609)

[Joachim Breitner]

Hi,

ah, yes, I’m in favor!

Cheers,
Joachim

Am Dienstag, dem 03.10.2023 um 11:17 +0100 schrieb Simon Peyton Jones:
> Chris
> 
> Joachim, Simon, and Richard have yet to vote; but I think you have a
> majority anyway.  Would you like to move this forward?
> 
> Simon
> 
> On Fri, 8 Sept 2023 at 11:57, Chris Dornan <chris at chrisdornan.com>
> wrote:
> > Proposal: Amend or patterns (#522) to use p1 ; p2 (#609)
> > Author: Sebastian Graf, David Knothe
> > Rendered proposal:
> > https://github.com/ghc-proposals/ghc-proposals/blob/eb4b67c29282520b2c5c6a49c3047dbecb15dde1/proposals/0522-or-patterns.rst
> > Discussion: https://github.com/ghc-proposals/ghc-proposals/pull/609
> > Recommendation: Acceptance
> > 
> > ## Summary
> > 
> > This proposal refines the syntax of an already accpted proposal
> > (#522) for writing or patterns.
> > 
> > The syntax of the old proposal,
> > 
> > ```haskell
> >     stringOfT :: T -> Maybe String
> >     stringOfT (T1 s)              = Just s
> >     stringOfT (one of T2{}, T3{}) = Nothing
> > ```
> > 
> > is replaced with
> > 
> > ```haskell
> >     stringOfT :: T -> Maybe String
> >     stringOfT (T1 s)       = Just s
> >     stringOfT (T2{}; T3{}) = Nothing
> > ```
> > 
> > or indeed
> > 
> > ```haskell
> >     stringOfT :: T -> Maybe String
> >     stringOfT x = case x of
> >       T1 s -> Just s
> >       T2{}
> >       T3{} -> Nothing
> > ```
> > 
> > (Beacuse the '(' ... ')' are optional here, we can remove them and
> > naturally exploit layout.)
> > 
> > The authors have conducted polls to see what folks preferred,
> > landing on this proposal. The
> > adjustments to the Haskell grammar are really quite minimal
> > requiring one extra production.
> > 
> > ## Recommendation
> > 
> > The proposal is nondiruptive and as a whole addresses an important
> > practical topic. I recommend
> > that we accept it
> > 
> > _______________________________________________
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> > ghc-steering-committee at haskell.org
> > https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee
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-- 
Joachim Breitner
  mail at joachim-breitner.de
  http://www.joachim-breitner.de/