61 lines
1.6 KiB
Haskell
61 lines
1.6 KiB
Haskell
|
module BasicLibrariesScratch where
|
||
|
|
|
||
|
|
import Data.Function ((&))
|
||
|
|
|
||
|
|
--------------------------------------------------------------------------------
|
||
|
|
newtype DList a = DL { unDL :: [a] -> [a] }
|
||
|
|
|
||
|
|
instance (Show a) => Show (DList a) where
|
||
|
|
show (DL x) = "DL " ++ show (x [])
|
||
|
|
|
||
|
|
-- | Create an empty difference list.
|
||
|
|
emptyDList :: DList a
|
||
|
|
emptyDList = DL $ \xs -> xs
|
||
|
|
{-# INLINE emptyDList #-}
|
||
|
|
|
||
|
|
-- | Create a difference list with `x` as the only member.
|
||
|
|
singleton :: a -> DList a
|
||
|
|
singleton x = DL $ \xs -> x : xs
|
||
|
|
{-# INLINE singleton #-}
|
||
|
|
|
||
|
|
-- | Convert the DList into a list.
|
||
|
|
toList :: DList a -> [a]
|
||
|
|
toList (DL unDL) = unDL mempty
|
||
|
|
{-# INLINE toList #-}
|
||
|
|
|
||
|
|
-- | Add an element to the end of a DList.
|
||
|
|
infixr `snoc`
|
||
|
|
snoc :: a -> DList a -> DList a
|
||
|
|
snoc x (DL xs) = DL $ \ys -> xs (x : ys)
|
||
|
|
{-# INLINE snoc #-}
|
||
|
|
|
||
|
|
-- | Add an element to the beginning of a DList.
|
||
|
|
infixr `cons`
|
||
|
|
cons :: a -> DList a -> DList a
|
||
|
|
cons x (DL xs) = DL $ \ys -> x : xs ys
|
||
|
|
{-# INLINE cons #-}
|
||
|
|
|
||
|
|
-- | Combine two DLists together.
|
||
|
|
append :: DList a -> DList a -> DList a
|
||
|
|
append (DL xs) (DL ys) = DL $ \zs -> zs & ys & xs
|
||
|
|
{-# INLINE append #-}
|
||
|
|
|
||
|
|
--------------------------------------------------------------------------------
|
||
|
|
data Queue a =
|
||
|
|
Queue { one :: [a]
|
||
|
|
, two :: [a]
|
||
|
|
} deriving (Show, Eq)
|
||
|
|
|
||
|
|
emptyQueue :: Queue a
|
||
|
|
emptyQueue = Queue mempty mempty
|
||
|
|
|
||
|
|
enqueue :: a -> Queue a -> Queue a
|
||
|
|
enqueue x (Queue en de) = Queue (x:en) de
|
||
|
|
|
||
|
|
dequeue :: Queue a -> Maybe (a, Queue a)
|
||
|
|
dequeue (Queue [] []) = Nothing
|
||
|
|
dequeue (Queue en []) =
|
||
|
|
let (d:de) = reverse en
|
||
|
|
in Just (d, Queue de [])
|
||
|
|
dequeue (Queue en (d:de)) = Just (d, Queue en de)
|