[Haskell-beginners] How to manage typeclass hierarchies and instances?

PATRICK BROWNE patrick.browne at dit.ie
Sun Feb 22 08:07:44 UTC 2015


  OPPS! My previous email should have be stated as a question rather than a
statement!

   class (Num a, Group a) => Additive a
  Or maybe given ( Additive a) => (Num a AND Group a).
  Then (Num a AND Group a) is a necessary condition for  (Additive a) to
hold.

On 22 February 2015 at 07:53, PATRICK BROWNE <patrick.browne at dit.ie> wrote:

>
> On 22 February 2015 at 00:04, Brandon Allbery <allbery.b at gmail.com> wrote:
>
>> You can't, at present. (Note: Typeclasses are not OOP classes; `class
>> (Num a, Group a) => Additive a` does not declare superclasses, but
>> prerequisites.)
>>
>
> In logic we would say (Num a AND Group a) is a necessary condition for (
> Additive a) => (Num a AND Group a) to hold.
>
>

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