On Mon, Apr 26, 2010 at 2:55 PM, Thomas van Noort
On 26-4-2010 20:12, Daniel Fischer wrote:
Am Montag 26 April 2010 19:52:23 schrieb Thomas van Noort:
...
Yes, y's type is more general than the type required by f, hence y is an acceptable argument for f - even z :: forall a b. a -> b -> Bool is.
That's what I thought. I've just never seen such a notion of a more general type involving overloading before.
However, it requires y to throw away the provided dictionary under the hood, which seems counter intuitive to me.
Why? y doesn't need the dictionary, so it just ignores it.
Sure, but y's type explicitly mentions that it doesn't want a dictionary, so why would you provide one to it?
Actually, y's type doesn't say anything at all about dictionaries.
That's a detail about GHC's implementation.
y's type says it will accept two values of any type. f's type says it
will provide two values of a type which is an instance of Eq.
--
Dave Menendez