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

[Eric Seidel]

I'm happy with this change.

On Fri, Sep 29, 2023, at 08:46, Moritz Angermann wrote:
> Sounds good to me. 
>
> On Fri, 29 Sep 2023 at 7:47 PM, Chris Dornan <chris at chrisdornan.com> wrote:
>> All,
>> 
>> This proposal has now been revised to make it non-disruptive. 
>> 
>> That was the only issue of substance that surfaced in our discussion and I recommend that we accept this revised proposal.
>> 
>> Chris
>> 
>> 
>>> On 8 Sep 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
>>> 
>> 
>> _______________________________________________
>> ghc-steering-committee mailing list
>> ghc-steering-committee at haskell.org
>> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee
> _______________________________________________
> ghc-steering-committee mailing list
> ghc-steering-committee at haskell.org
> https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee