I don't know Purescript so couldn't say about that. In standard Haskell you don't need to use forall at all; it's used by this extension and by extensions for existential types. On Thu, Apr 12, 2018 at 4:24 PM, Dennis Raddle <dennis.raddle@gmail.com> wrote:
Thanks!
By the way, why do I sometimes have to use forall, and sometimes not?
I'm also learning Purescript, and I noticed that the examples use 'forall' in every case. Why would it be different with Purescript? D
On Thu, Apr 12, 2018 at 12:51 PM, Brandon Allbery <allbery.b@gmail.com> wrote:
On Thu, Apr 12, 2018 at 3:47 PM, Dennis Raddle <dennis.raddle@gmail.com> wrote:
myFunc :: a -> b -> c myFunc x y z = ... where helper :: a -> [b] helper xx = ...
Notice that I'm attempting to declare 'helper' using my type variables. I've noticed that this results in an error. Is this actually possible, and how?
You need the ScopedTypeVariables extension, *and* to "declare" the type variables whose scope is to be extended with an explicit "forall" in the signature.
-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net
-- brandon s allbery kf8nh sine nomine associates allbery.b@gmail.com ballbery@sinenomine.net unix, openafs, kerberos, infrastructure, xmonad http://sinenomine.net