Updating/understanding code from implicit configurations paper
Eric M. Pashman
eric.pashman at gmail.com
Sat Jan 19 01:13:43 CET 2013
Whoops. I forgot you need the explicit `forall` with scoped type variables. I thought there was something much more involved going on here. Thanks, Shachaf.
On Jan 18, 2013, at 17:54 , Shachaf Ben-Kiki <shachaf at gmail.com> wrote:
> On Fri, Jan 18, 2013 at 3:32 PM, Eric M. Pashman <eric.pashman at gmail.com> wrote:
>> normalize :: (Modular s a, Integral a) => a -> M s a
>> normalize x = (M (mod x (modulus (undefined :: s)))) :: M s a
> If you want your type variables to be scoped, you have to annotate
> them explicitly:
> normalize :: forall s a. (Modular s a, Integral a) => a -> M s a
> normalize x = M (mod x (modulus (undefined :: s)))
> See <http://www.haskell.org/ghc/docs/7.4.2/html/users_guide/other-type-extensions.html#scoped-type-variables>.
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