Indeed, it's reasonable to mix and match Peano naturals with TypeLits. But that's easily done in a library that exposes a Haskell 98 interface over a TypeLits-based implementation. I don't think everyone should have to pay the potential efficiency price of Peano naturals for the sake of standards purity. On Mon, Sep 17, 2018, 2:37 PM Henning Thielemann < lemming@henning-thielemann.de> wrote:
On Mon, 17 Sep 2018, andrew.lelechenko@gmail.com wrote:
Instead of having
``` data E0
instance HasResolution E0 where resolution _ = 1 ```
and repeating it as many times as there are `E` datatypes, I propose to add the following type:
``` {-# LANGUAGE DataKinds #-} {-# LANGUAGE KindSignatures #-}
import GHC.TypeLits (Nat, KnownNat, natVal)
data E (n :: Nat) ```
I'd prefer a Haskell 98 solution and simply use type level Peano numbers and define E0, E3 etc. as type synonyms. If this is not sufficiently compatible we could setup a new module._______________________________________________ Libraries mailing list Libraries@haskell.org http://mail.haskell.org/cgi-bin/mailman/listinfo/libraries