Dear,
After having read Bulat's mail regarding TH when I had mentioned my wish
for Pretty, I decided to use TH for a much smaller project. That's why
today I have created an automated derivation for data constructor
filtering. As I started coding someone mentioned that something similar
can be done with list comprehensions, so I'm not certain about the scope
of usefulness, however personally I have found the need for this at
times. Anyways, the code can be obtained from the darcs repo at
http://oasis.yi.org:8080/repos/haskell/filter
Suggestions, bugs, additions are always welcome :)
Here is an example:
{-# OPTIONS_GHC -fglasgow-exts -fth #-}
module Main where
import Filter
data T = A Int String | B Integer | C deriving Show
data Plop a b = Foo a | Bar b deriving Show
$(deriveFilter ''T)
$(deriveFilter ''Plop)
main :: IO ()
main = do
let l = [A 1 "s", B 2, C]
let l2 = [Foo 1, Bar "a", Foo 2, Bar "b"]
print l
print $ filter isA l
print l2
print $ filter isFoo l2
Cheers
Christophe ([EMAIL PROTECTED])
--
Christophe Poucet
Ph.D. Student
Phone:+32 16 28 87 20
E-mail: Christophe (dot) Poucet (at) imec (dot) be
Website: http://notvincenz.com/
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