Try
test' = square . (4 :: a -> (Integer,a))
Otherwise, how is the compiler to know that you want 4 to be of that
type?
S
| -Original Message-
| From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED] On Behalf Of Greg
| Buchholz
| Sent: 26 October 2006 18:46
| To: haskell-cafe@haskell.org
|
You need to monomorphize the result before printing:
main = print $ ((square . 4) :: Alpha ())
Presumably you will apply (square . 4) at some point to a concrete state
at some point, and you wouldn't need to provide the type explicitly.
Greg Buchholz wrote:
Dan Weston wrote:
How about:
Dan Weston wrote:
> How about:
Hmm. I'm probably being dense today, but when I add the following
definitions to your program...
main = print $ (square . 4) ()
square (a,b) = (a*a,b)
...I still get the same error...
No instance for (Num (() -> (t, t1)))
arising from the literal `
How about:
{-# OPTIONS -fglasgow-exts #-}
import Control.Arrow
type Alpha alpha = alpha -> (Integer,alpha)
test = square . (lit 4)
lit :: Integer -> Alpha alpha
lit val stack= (val, stack)
instance Eq (Alpha alpha) where
x == y = uncurry (==) . (fst . x &&& fst . y) $ undefined
insta
