Can anyone explain the following error message from Hug98 (with extensions enabled)?
I have
> class Space t > class Space t => HasY v t > where > assignY :: v -> t -> t > getY :: t -> v > varY :: forall w . Space w => v -> (t->t) -> (w->w)
I get an error on the last definition "quantifier does not mention type variable v" (and if I quantify v, then it complains that t is not quantified).
The idea I'm trying to express is that for any instance of HasY v t
there should be a function varY with type
v -> (t->t) -> (w->w)
for some type w of class Space.Any help much appreciated.
Is there any kind of tutorial introduction to "forall" out there?
Cheers, Theo Norvell
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