[Haskell-cafe] Re: type families and type signatures

Stefan Monnier monnier at iro.umontreal.ca
Mon Apr 7 16:04:21 EDT 2008

> Id is an operation over types yielding a type, as such it doesn't make
> much sense to me to have (Id a -> Id a) but rather something like (a ->
> Id a).

Actually, it can make perfect sense: e.g. if the `Id' function acts as
a constraint.


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