blob: bb1f89987e290dcf0e639c0eb3e6ddd5d86f03f6 (
plain) (
blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
|
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)
|
