On Mon, Feb 13, 2012 at 6:07 AM, Bas van Dijk
Edward,
it was my impression that you have to use ScopedTypeVariables or other tricks to work with Proxy to.
But with Tagged the situation is similar:
{-# LANGUAGE ScopedTypeVariables #-} typeOf :: forall a. Typeable a => a -> TypeRep typeOf _ = unTagged (typeRep :: Tagged a TypeRep)
or without extensions:
typeOf :: Typeable a => a -> TypeRep typeOf x = unTagged (t x) where t :: Typeable b => b -> Tagged b TypeRep t _ = typeRep
Where is the "huge pain" you are talking about?
The pain is the need to define t. With Proxy you can often use pre-existing combinators, because as a data type, it admits a ton of instances. In this case you can just use 'return' or 'pure'. typeOf :: Typeable a => a -> TypeRep typeOf = typeRep . pure There are fewer combinators from commonly used classes for working with the left argument of a bifunctor, however. -Edward