#11534: Allow class associated types to reference functional dependencies -------------------------------------+------------------------------------- Reporter: ekmett | Owner: Type: feature request | Status: new Priority: normal | Milestone: Component: Compiler (Type | Version: 7.10.3 checker) | Keywords: TypeFamilies, Resolution: | FunctionalDependencies Operating System: Unknown/Multiple | Architecture: | Unknown/Multiple Type of failure: Other | Test Case: Blocked By: | Blocking: Related Tickets: | Differential Rev(s): Wiki Page: | -------------------------------------+------------------------------------- Comment (by simonpj):
I can't define {{{ type Fun c d f = Functor (Dom f) (Cod f) f }}} No indeed. So don't. Just have a single-parameter `Functor` class! {{{ class Functor (f :: i -> j) where type Dom f :: i -> i -> * type Cod f :: j -> j -> * }}} Now, I understand you are saying "a single-parameter `Functor` class is exactly what I would like but there is a problem". So rather than fix difficulties with the workaround, let's fix the actual problem. What exactly is it? What type family do you need to partially apply? So far we have `Dom` and `Cod`. Do you need to partially apply those? Can you just walk me through slowly the exact problem with the direct approach?
-- Ticket URL: http://ghc.haskell.org/trac/ghc/ticket/11534#comment:10 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler