Here's a type that fits:
d :: forall b a t c. (F t c b, F t a c) = t - a - b
from the following code:
-# OPTIONS -fglasgow-exts #-}
module Main where
main :: IO ()
main = putStrLn OK
data ID = ID
data HEAD = HEAD
data FST = FST
class F t a b | t a - b where
f :: t - a - b
instance F
Is there a type we can give to
y f = f . f
y id
y head
y fst
are all typeable?
Jim Apple
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On Mon, 28 Feb 2005 03:50:14 -0500
Jim Apple [EMAIL PROTECTED] wrote:
Is there a type we can give to
y f = f . f
y id
y head
y fst
are all typeable?
Using ghci:
Prelude let y f = f.f
Prelude :t y
y :: forall c. (c - c) - c - c
So it admits principal type (a-a) - a-a. From this
The name y suggests that you want to define the fixpoint combinator.
This works as follows:
Prelude let y f = f (y f)
Prelude :type y
y :: forall t. (t - t) - t
Prelude y (\fac n - if n == 0 then 1 else n*fac(n-1)) 10
3628800
Prelude
Till
Pedro Vasconcelos wrote:
On Mon, 28 Feb 2005 03:50:14 -0500
Pedro Vasconcelos wrote:
Jim Apple [EMAIL PROTECTED] wrote:
Is there a type we can give to
y f = f . f
y id
y head
y fst
are all typeable?
Using ghci:
Prelude let y f = f.f
Prelude :t y
y :: forall c. (c - c) - c - c
So it admits principal type (a-a) - a-a. From this you can see that
(y
On 2005-02-28 at 18:03GMT Ben Rudiak-Gould wrote:
Pedro Vasconcelos wrote:
Jim Apple [EMAIL PROTECTED] wrote:
Is there a type we can give to
y f = f . f
y id
y head
y fst
are all typeable?
Using ghci:
Prelude let y f = f.f
Prelude :t y
y :: forall c. (c - c) -
Jon Fairbairn writes:
On 2005-02-28 at 18:03GMT Ben Rudiak-Gould wrote:
Pedro Vasconcelos wrote:
Jim Apple [EMAIL PROTECTED] wrote:
Is there a type we can give to
y f = f . f
y id
y head
y fst
are all typeable?
Using ghci:
Prelude let y f = f.f
