Heterogeneous equality into base?

David Feuer david.feuer at gmail.com
Mon Jul 10 16:20:17 UTC 2017

There's another version of heterogeneous equality that takes its
arguments in the other order. I'm not sure if this is generally useful
enough to want to include.

-- (:~~:) :: forall j k. j -> k -> *

data OtherEquality :: forall j. j -> forall k. k -> Type where
  OtherRefl :: OtherEquality a a

On Mon, Jul 10, 2017 at 11:24 AM, Ryan Scott <ryan.gl.scott at gmail.com> wrote:
> I also agree that we should keep HRefl a distinct name, and moreover, we
> should keep :~: and :~~: as distinct datatypes.
> I'm also on-board with the idea that we should introduce a separate
> Data.Type.Equality.Hetero module that reexports :~~: and defines
> heterogeneous counterparts for sym, trans, etc. from Data.Type.Equality. I
> don't have a strong opinion on how they should be named (e.g., sym vs.
> hsym).
> Ryan S.
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