Hi list,
I have stumbled upon a strange annoyance:
{-# LANGUAGE GADTs #-}
data Foo v where
Foo :: Foo (Maybe v)
-- This doesn't work
foo1 :: a - Foo a - Int
foo1 Nothing Foo = undefined
foo1 (Just x) Foo = undefined
-- This does
foo2 :: a - Foo
Francesco Mazzoli f at mazzo.li writes:
I have stumbled upon a strange annoyance:
{-# LANGUAGE GADTs #-}
Hi Francesco, I think you'll find that the 'annoyance' is nothing to do
with GADTs. I suggest you take the type signature off of foo1, and see
what type ghc infers for it. It
At Wed, 19 Jun 2013 10:03:27 + (UTC),
AntC wrote:
Hi Francesco, I think you'll find that the 'annoyance' is nothing to do
with GADTs. I suggest you take the type signature off of foo1, and see
what type ghc infers for it. It isn't :: a - Foo a - Int.
[...]
Yep, that message explains
On Wed, Jun 19, 2013 at 11:11:16AM +0100, Francesco Mazzoli wrote:
At Wed, 19 Jun 2013 10:03:27 + (UTC),
AntC wrote:
Hi Francesco, I think you'll find that the 'annoyance' is nothing to do
with GADTs. I suggest you take the type signature off of foo1, and see
what type ghc infers for
At Wed, 19 Jun 2013 06:59:00 -0400,
Brent Yorgey wrote:
Yes, I was going to suggest switching the argument order before
reading your message. This is an interesting way in which you can
observe that Haskell does not really have multi-argument functions.
All multi-argument functions are really
Brent, maybe I'm misunderstanding what you're saying, but I don't
think that the order of the arguments is playing any role here besides
defining the order in which the pattern matches are desugared.
To illustrate,
-- This does work
foo1' :: a - Foo a - Int
foo1' m Foo = case m of
Good point. I stand corrected.
-Brent
On Wed, Jun 19, 2013 at 11:42:23AM -0300, Felipe Almeida Lessa wrote:
Brent, maybe I'm misunderstanding what you're saying, but I don't
think that the order of the arguments is playing any role here besides
defining the order in which the pattern matches
