GHC.Generics and instances of Functor, Applicative, etc?

Conal Elliott conal at
Wed Jan 13 03:26:08 UTC 2016

Lovely. Thanks!

On Tue, Jan 12, 2016 at 7:23 PM, Edward Kmett <ekmett at> wrote:

> is the current ticket for
> tracking this and has more details.
> On Tue, Jan 12, 2016 at 8:28 PM, Conal Elliott <conal at> wrote:
>> I'm using GHC.Generics and have noticed that the data types defined there
>> don't have instances of the standard classes (at least not defined in that
>> module), such as Functor, Applicative, Foldable and Traversable. It'd be
>> very useful to be able to rely on such instances, so that one can define
>> instances of custom types via instances of the generic types. (Hopefully,
>> the compiler can remove most or all conversion overhead) Is there any
>> reason not to add these generic instances?
>> -- Conal
>> _______________________________________________
>> Libraries mailing list
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