Ralf Lammel wrote:
What you can do is define a dedicated *type code* for composition.
comp = hFoldr (undefined::Comp) (id::Int - Int) test
data Comp
instance Apply Comp (x - y,y - z) (x - z)
where
apply _ (f,g) = g . f
That does it!
Thanks,
Greg Buchholz
I was playing around with the HList library from the paper...
Strongly typed heterogeneous collections
http://homepages.cwi.nl/~ralf/HList/
...and I thought I'd try to fold the composition function (.) through a
heterogeneous list of functions, using hFoldr...
{-# OPTIONS
-Original Message-
From: [EMAIL PROTECTED] [mailto:haskell-cafe-
[EMAIL PROTECTED] On Behalf Of Greg Buchholz
Sent: Sunday, November 06, 2005 7:01 PM
To: haskell-cafe@haskell.org
Subject: [Haskell-cafe] Type classes and hFoldr from HList
I was playing around with the HList library from
