[Haskell-cafe] Type constraint rewrite rules

[Henning Thielemann]

On Mon, 23 Jan 2023, Anthony Clayden wrote:

> > ... rewrite rules for type constraints ...

> That's what FunDeps are, with the advantage you can stipulate 
> multiple/multi-directional rewrites.

How would you simplify Forth (Back a) to 'a' automatically with FunDeps?

I could define

   class ForthBack a b | a -> b, b -> a where

but then I would have constraint ForthBack a b and it does not go away.