Re: [Haskell-cafe] Closed Type Family Simplification

Actually, that example is not quite right. Let me try to come up with another one. On Wednesday, August 13, 2014 6:54:45 PM UTC-7, Richard Eisenberg wrote:

Your operating assumption sounds right. Do you have a complete, minimal example showing the error? If not, I recommend using -fprint-explicit-kinds to see if kinds are getting in your way at all.

Richard

On Aug 13, 2014, at 8:02 PM, Ian Milligan javascript:> wrote:

...

When a closed type family has only one instance it seems like it should never fail to simplify. Yet this doesn't appear to be the case. When I defined (in GHC 7.8.3) the closed type family type family (:.:) f g a where (:.:) f g a = f (g a) I get errors such as 'Could not deduce (Object c3 ((:.:) f g a) ~ Object c3 (f (g a)))' (where Object is a Constraint family), indicating that f (g a) is not being substituted for (:.:) f g a as desired. Any idea why this happens? _______________________________________________ Haskell-Cafe mailing list Haskel...@haskell.org javascript: http://www.haskell.org/mailman/listinfo/haskell-cafe

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