Proposal: Remove Show and Eq superclasses of Num
jon.fairbairn at cl.cam.ac.uk
Sun Sep 18 10:54:52 CEST 2011
Malcolm Wallace <malcolm.wallace at me.com> writes:
>> The first 2 attached patches (for base and ghc respectively) remove the
>> Show constraint. I'm not aware of any justification for why this
>> superclass makes sense.
> I'm strongly in favour of removing the Show constraint.
>> The next 2 patches (for base and unix respectively) remove the Eq
>> constraint. Here's there's some justification in the superclass, as it
>> f 5 = ...
>> work for any Num type, rather than also needing an Eq constraint,
> I am undecided whether removing the Eq constraint is a good
> thing or not. In principle, yes, it makes perfect sense. But
> in practice, the example you give of pattern-matching a
> literal now requiring an Eq context, smells slightly wrong to
But pattern matching for Double or Float is a Bad Thing, so
wouldn’t the solution to this be to put the EQ constraint
somewhere else, such as Integral where it would be less
Jón Fairbairn Jon.Fairbairn at cl.cam.ac.uk
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