doublylinked/test.icl

   1 module test
   2
   3 :: DList a = Nil | Cons a (Link (DList a))
   4 :: Link a = {prev :: a, next :: a}
   5
   6 fromList :: ([a] -> DList a)
   7 fromList = go Nil
   8 where
   9         go :: (DList a) [a] -> DList a
  10         go prev [] = Nil
  11         go prev [a:as] =
  12                 let head = Cons a {prev=prev,next=tail}
  13                     tail = go head as
  14                 in head
  15
  16 toList :: (DList a) -> [a]
  17 toList Nil = []
  18 toList (Cons el {next}) = [el:toList next]
  19
  20 nil :: DList a
  21 nil = Nil
  22
  23 (:!) infixr 0 :: a (DList a) -> DList a
  24 (:!) elh Nil = Cons elh {prev=nil,next=nil}
  25 (:!) elh (Cons elt link) =
  26         let tail = Cons elt {link & prev=head}
  27             head = Cons elh {prev=nil,next=tail}
  28         in head
  29
  30 Start =
  31         (toList (1 :! 2 :! 3 :! nil)
  32         ,toList (fromList [1,2,3])
  33         )