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 vogt.a...@gmail.com
On Sat, Jul 20, 2013 at
On Sat, Jul 20, 2013 at 12:31 AM, Carter Schonwald
carter.schonw...@gmail.com 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
On Fri, Jul 19, 2013 at 5:19 AM, Jose A. Lopes jabolo...@google.com 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
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,
