-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA1 List, I'm trying to wrap my head around Haskell and Category Theory---very new to both and in keeping with character, I've jumped into the deep-end. The categories and category-extras packages have helped to illustrate some concepts. However, I remain confused and hope someone can point me in the right direction. The ultimate goal is to construct my own instance of a CCC. Here is the class definition for CCC from the categories package:
class ( Cartesian (<=) , Symmetric (<=) (Product (<=)) , Monoidal (<=) (Product (<=)) ) => CCC (<=) where type Exp (<=) :: * -> * -> * apply :: (Product (<=) (Exp (<=) a b) a) <= b curry :: ((Product (<=) a b) <= c) -> a <= Exp (<=) b c uncurry :: (a <= (Exp (<=) b c)) -> (Product (<=>) a b <= c)
I have the following:
{-# LANGUAGE TypeFamilies, MultiParamTypeClasses, UndecidableInstances #-}
import Control.Category.Braided import Control.Category.Associative import Control.Category.Cartesian import Control.Category.Monoidal import Control.Category.Cartesian.Closed
data MyType a b = MyType {f::(a -> b)} data SomeType a b = SomeType {g::(a,b)}
instance (Symmetric MyType (Product MyType), Monoidal MyType (Product MyType), PreCartesian MyType) => CCC MyType where
type Exp MyType = SomeType
It type checks in ghci and gives the appropriate warnings that apply, curry and uncurry have not been defined---I can't see how to define these. Is it actually possible with the two data types I have? I would really appreciate some help. Lafras -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.10 (GNU/Linux) Comment: Using GnuPG with Mozilla - http://enigmail.mozdev.org/ iEYEARECAAYFAkyaGWYACgkQKUpCd+bV+kqgWgCfY7B7pUttB0xfeOAN1V3NDqRL fgQAniK/EJsV9jS7XWxmxElCVD6AW0as =l0x/ -----END PGP SIGNATURE-----