The paper makes the (somewhat radical) case for not generalising local bindings
at all; which would at a stroke remove most of the issues of the MR. (We'd
still need to think about the top level.)
We'd love to know what any of you think of the idea.
I read the paper (except section 5 which is very technical).
I like that it makes
(let x = ... in ...)
behave the same as
(\x -> ...) (...)
. Understanding how to respond to type inference and error messages is
hard enough without having additional differences in innocent-looking
code. Do you think my hope is reasonable that not-generalizing could
lead to better error messages? I don't quite understand the issues[*],
but I suspect that not-generalizing would at least make *me* less
confused when fixing error messages because there are fewer different
typechecker behaviors to think about. I guess it's still possible to
use explicit type-signatures to make let-bindings polymorphic, in a way
that is difficult or impossible for lambda or case? (I guess for lambda,
it would require making the lambda into a rank-2 function, though I'm
not sure how to do that syntactically.)
[*] e.g., the gmapT / rank-2 example confuses me; would it work if
(...blah...) were passed directly to gmapT without the let?
Also, does it happen to solve the 2^n worst-case typechecking?
-Isaac
_______________________________________________
Haskell-prime mailing list
Haskell-prime@haskell.org
http://www.haskell.org/mailman/listinfo/haskell-prime
