You can define:
data EqDyn= forall a.(Typeable a, Eq a)=> EqDyn a
instance Eq EqDyn where
(EqDyn x) == (EqDyn y)= typeOf x== typeOf y && x== unsafeCoerce y
unsafeCoerce is safe synce the expression assures that types are equal
2013/7/20 adam vogt
> On Sat, Jul 20, 2013 at 12:31 AM, Carte
On Sat, Jul 20, 2013 at 12:31 AM, Carter Schonwald
wrote:
> the tricky part then is to add support for other types.
>
> another approach to existentially package type classes with the data type!
>
> eg
> data HasEq = forall a . HasEq ( Eq a => a)
> or its siblinng
> data HasEq a = Haseq (Eq a =>
the tricky part then is to add support for other types.
another approach to existentially package type classes with the data type!
eg
data HasEq = forall a . HasEq ( Eq a => a)
or its siblinng
data HasEq a = Haseq (Eq a => a )
note this requires more planning in how you structure your program,
On Fri, Jul 19, 2013 at 5:19 AM, Jose A. Lopes wrote:
> Hello,
>
> How to define equality for Data.Dynamic ?
Hi Jose,
You could try casting the values to different types that do have an
(==). You can treat the case where you have the types matching, but
didn't list that type beforehand different
