module Data.Text.Fusion.Internal
(
M(..)
, M8
, PairS(..)
, S(..)
, Step(..)
, Stream(..)
, Switch(..)
, empty
) where
import Data.Word (Word8)
data M a = N
| J !a
deriving (Eq, Ord, Show)
type M8 = M Word8
data S s = S !s
!M8 !M8 !M8
deriving (Eq, Ord, Show)
infixl 2 :!:
data PairS a b = !a :!: !b
deriving (Eq, Ord, Read, Show)
data Switch = S1 | S2
deriving (Eq, Ord, Show)
data Step s a = Done
| Skip !s
| Yield !a !s
instance Show a => Show (Step s a)
where show Done = "Done"
show (Skip _) = "Skip"
show (Yield x _) = "Yield " ++ show x
instance (Eq a) => Eq (Stream a) where
(==) = eq
instance (Ord a) => Ord (Stream a) where
compare = cmp
data Stream a =
forall s. Stream
(s -> Step s a)
!s
!Int
eq :: (Eq a) => Stream a -> Stream a -> Bool
eq (Stream next1 s1 _) (Stream next2 s2 _) = loop (next1 s1) (next2 s2)
where
loop Done Done = True
loop (Skip s1') (Skip s2') = loop (next1 s1') (next2 s2')
loop (Skip s1') x2 = loop (next1 s1') x2
loop x1 (Skip s2') = loop x1 (next2 s2')
loop Done _ = False
loop _ Done = False
loop (Yield x1 s1') (Yield x2 s2') = x1 == x2 &&
loop (next1 s1') (next2 s2')
cmp :: (Ord a) => Stream a -> Stream a -> Ordering
cmp (Stream next1 s1 _) (Stream next2 s2 _) = loop (next1 s1) (next2 s2)
where
loop Done Done = EQ
loop (Skip s1') (Skip s2') = loop (next1 s1') (next2 s2')
loop (Skip s1') x2 = loop (next1 s1') x2
loop x1 (Skip s2') = loop x1 (next2 s2')
loop Done _ = LT
loop _ Done = GT
loop (Yield x1 s1') (Yield x2 s2') =
case compare x1 x2 of
EQ -> loop (next1 s1') (next2 s2')
other -> other
empty :: Stream a
empty = Stream next () 0
where next _ = Done