W/examples/sample.w

   1 ># sample.w
   2  #
   3  # sneek preview for the world!
   4  #<
   5
   6 import StdEnv
   7
   8 typedef Tree a := Tip | Bin a (Tree a) (Tree a)
   9
  10 # functions are invoked as 'insert(x, y)'
  11 func insert : a (Tree a) -> (Tree a)
  12 insert(x, Tip) = Bin x Tip Tip
  13 insert(x, Bin y l r) | x < y = Bin y insert(x, l) r
  14                      | otherwise = Bin y l insert(x, r)
  15
  16 # prefix operators work like normal functional functions
  17 op prefix contains : a (Tree a) -> B
  18 contains x Tip = False
  19 contains x (Bin y l r) | x == y = True
  20                        | x < y = contains x l
  21                                            | otherwise = contains x r
  22
  23 op prefix len : [a] -> N
  24 len [] = 0
  25 len [_:xs] = 1 + (len xs)
  26
  27 # currently no way to specify binding strenght
  28 op infix -- : N N -> B
  29 -- x y | x < y = True
  30        | otherwise = False
  31
  32 func max : N N -> N
  33 max(x, y) | x -- y = y
  34           | y -- x = x
  35                   | otherwise = y # equals
  36