data-reify-0.1: test/Test2.hs

{-# LANGUAGE TypeFamilies #-}
module Main where

import qualified Data.Traversable as T
import qualified Data.Foldable as F
import Data.Monoid
import Control.Applicative hiding (Const)
import Data.Unique
import Data.Unsafe.Reify
import Control.Monad

-- Notice how there is nothing Mu-ish about this datatype.
data State a b = State a [(b,State a b)]
        deriving Show

s0 = State 0 [(True,s1),(False,s2)]
s1 = State 1 [(True,s0),(False,s1)]
s2 = State 2 [(True,s1),(False,s0)]

data StateDeRef a b r = StateDeRef a [(b,r)]
        deriving Show

instance MuRef (State a b) where
   type DeRef (State a b) = StateDeRef  a b
   deRef (State a tr) = StateDeRef a tr
   mapDeRef f (StateDeRef a tr) = liftM (StateDeRef a) $ mapM (\ (b,s) -> liftM ((,) b) $ (f s)) tr

instance Functor (StateDeRef a b) where
   fmap f (StateDeRef a tr) = StateDeRef a [ (b,f s) | (b,s) <- tr ]


main = do
        reifyGraph s0 >>= print