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

[Moritz Angermann]

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
>
>
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