[Haskell-cafe] Equality constraints in type families

Hugo Pacheco hpacheco at gmail.com
Sun Mar 30 00:14:08 EDT 2008

On Sun, Mar 30, 2008 at 3:54 AM, Manuel M T Chakravarty <
chak at cse.unsw.edu.au> wrote:

> Hugo Pacheco:
> > Yes, but doesn't the confluence problem only occur for type synonyms
> > that ignore one or more of the parameters? If so, this could be
> > checked...
> You can't check this easily (for the general case).

I was most interested in knowing that this assumption was enough, and it
looks like it does.

> Given
>   type family G a b
>    type FList a x = G a x
>    type instance F [a] = FList a
> Does FList ignore its second argument?  Depends on the type instances
> of G.
> Manuel

I haven't thought of that, thanks for the example.

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