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

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 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/eb4b67c29282520b2c5c6a49... 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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