Hello,
perhaps it is time to come up with some sort of decision here. Based on
the replies to this thread we seem to have the following opinions:
1. Eric and Richard seem to be quite keen on the feature
2. Simon is on the fence, but likes it because it introduces System F
vocabulary to Haskell
3. I am skeptical of the proposal as is, as I think it adds additional
complexity to the language (more non-orthogonal features) without
significant payoff.
Does anyone else have anything else to add?
-Iavor
On Tue, Mar 26, 2019 at 6:48 PM Eric Seidel
On Tue, Mar 26, 2019, at 13:17, Iavor Diatchki wrote:
My concern is that the notation certainly suggests that you are binding types with the @ syntax, but in really it is still the type signature that guides the binding of the variables and the @ parameters just duplicate the information from the type signature.
But you are binding types with the @ syntax. The proposal gives a number of examples where the @-bound type variable is bound by a different name (or not at all) in the type signature. Many are contrived, to demonstrate where the binders are allowed, but the higher-rank and proxy-eliding examples look compelling to me.
We also already allow repeated value binders in Haskell. When I write a function in equational style, I have to rebind each argument in each alternate equation. Sometimes this is noisy and I'll prefer a single equation with an explicit `case`. But for functions where the body is sizable, I find the repeated binders to be quite helpful because the scopes are smaller. I can easily see the same benefit applying to type binders. Ultimately, I think this comes down to a matter of style, and I favor letting Haskell programmers pick the style that works best for them.
Eric _______________________________________________ ghc-steering-committee mailing list ghc-steering-committee@haskell.org https://mail.haskell.org/cgi-bin/mailman/listinfo/ghc-steering-committee