Re: MINIMAL XOR (Was: Proposal: Make Eq type class single method)

not necessarily ... there could be  contradictory sets of methods! :)

like the minimal sets for Field type class,  the xor would be for defining
'/' in terms of reciprocal and times or vice versa (/ vs recip) and
likewise (negate vs minus) etc etc

On Wed, Oct 27, 2021 at 6:38 AM Henning Thielemann <
[email protected]> wrote:

>
> On Mon, 25 Oct 2021, Carter Schonwald wrote:
>
> > i agree with Tom and Hecate,more strongly:
> >
> https://github.com/ghc/ghc/blob/98aa29d3fe447cce3407e6864b015892244bb475/libraries/ghc-prim/GHC/Classes.hs#L142-L150
>
> > the current definition DOES NOT require defining both.
> >
> > as it currently stands, you only need to define one of '==' XOR  '/='
> >
> > this actually suggests an interesting and DIFFERENT
> ecosystem improvement, (ignoring IEEE non-signalling NANs),
> > namely we add support for XOR to minimal pragma syntax and issue a
> warning
> >
> > perhaps something like adding (XOR "reason String" clauseExpr1
> clauseexpr2) ?
>
> The problem of implementing two methods in a contradictory way arises for
> any OR in MINIMAL pragma, right?

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