utils/mkUserGuidePart/DList.hs


1
2
3
4
5
6
7
8
9
10
11
12
13

module DList where

newtype DList a = DList ([a] -> [a])

snoc :: DList a -> a -> DList a
DList f `snoc` x = DList (f . (x:))

toList :: DList a -> [a]
toList (DList f) = f []

instance Monoid (DList a) where
  mempty = DList id
  DList a `mappend` DList b = DList (a . b)