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  • Glasgow Haskell CompilerGlasgow Haskell Compiler
  • GHCGHC
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  • #10592
Closed
Open
Issue created Jul 01, 2015 by MikeIzbicki@trac-MikeIzbicki

Allow cycles in class declarations

In particular, I would like to have a class hierarchy that looks like:

{-# LANGUAGE TypeFamilies #-}
{-# LANGUAGE FlexibleContexts #-}

type family Scalar x

class Field (Scalar x) => Vector x

class Vector x => Field x

It is the case that every field is a vector, and the scalar associated with every vector is a field. But we can't currently enforce that.

Edited Mar 10, 2019 by Ben Gamari
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