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September 14, 2017 17:34
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{-# LANGUAGE MultiParamTypeClasses #-} | |
{-# LANGUAGE FunctionalDependencies #-} | |
{-# LANGUAGE FlexibleInstances #-} | |
{-# LANGUAGE TypeOperators #-} | |
{-# LANGUAGE UndecidableInstances #-} | |
import Control.Compose | |
import Control.Monad.Trans.State.Lazy | |
import Data.Char | |
newtype Const b a = Const { unConst :: b } | |
newtype M m a = Wrap { unWrap :: m a } | |
instance Functor m => Functor (M m) where | |
fmap f x = Wrap (fmap f $ unWrap x) | |
instance Monad m => Applicative (M m) where | |
pure = Wrap . return | |
f <*> x = Wrap (unWrap f <*> unWrap x) | |
class Coerce a b | a -> b where | |
down :: a -> b | |
up :: b -> a | |
instance Coerce (Id a) a where | |
down = unId | |
up = Id | |
instance Coerce (Const b a) b where | |
down = unConst | |
up = Const | |
instance (Coerce (m a) b, Coerce (n a) c) => Coerce ((m :*: n) a) (b, c) where | |
down mxn = let (x, y) = unProd mxn in (down x, down y) | |
up (x, y) = Prod (up x, up y) | |
instance (Functor m, Functor n, Coerce (m b) c, Coerce (n a) b) => Coerce ((m :. n) a) c where | |
down = down . (fmap down) . unO | |
up = O . (fmap up) . up | |
instance Coerce (m a) c => Coerce (M m a) c where | |
down = down . unWrap | |
up = Wrap . up | |
-- Word Count | |
type Count = Const Integer | |
instance Functor Count where | |
fmap _ (Const x) = Const x | |
instance Applicative Count where | |
pure _ = Const 0 | |
(Const x) <*> (Const y) = Const $ x + y | |
instance Coerce (State s a) (s -> (a, s)) where | |
down = runState | |
up = state | |
count :: a -> Count b | |
count _ = Const 1 | |
cciBody :: Char -> Count a | |
cciBody = count | |
cci :: String -> Count [a] | |
cci = traverse cciBody | |
test :: Bool -> Integer | |
test b = if b then 1 else 0 | |
lciBody :: Char -> Count a | |
lciBody c = up (test (c == '\n')) | |
wciBody :: Char -> (M (State Bool) :. Count) a | |
wciBody c = up (updateState c) where | |
updateState :: Char -> Bool -> (Integer, Bool) | |
updateState c w = let s = not (isSpace c) in (test (not w && s), s) | |
wci :: String -> (M (State Bool) :. Count) [a] | |
wci = traverse wciBody | |
runWci :: String -> Integer | |
runWci s = fst (down (wci s) False) |
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