week3/camil/StdStack.icl

   1 implementation module StdStack
   2
   3 import StdEnv
   4 import StdList
   5
   6 :: Stack a :== [a]
   7
   8 newStack :: (Stack a)
   9 newStack = []
  10
  11 push :: a (Stack a) -> (Stack a)
  12 push a s = [a] ++ s
  13
  14 pop :: (Stack a) -> (Stack a)
  15 pop [a:s] = s
  16 pop [] = []
  17
  18 popn :: Int (Stack a) -> (Stack a)
  19 popn 0 s = s
  20 popn n s = popn (n-1) (pop s)
  21
  22 pushes :: [a] (Stack a) -> (Stack a)
  23 pushes [] s = s
  24 pushes a s = pushes (tl a) (push (hd a) s)
  25
  26 top :: (Stack a) -> a
  27 top [] = abort "`top s` with s = []"
  28 top s = hd s
  29
  30 topn :: Int (Stack a) -> [a]
  31 topn n s
  32         | n > length s = abort "`topn n s` with n > length s"
  33         | otherwise = take n s
  34
  35 count :: (Stack a) -> Int
  36 count s = length s
  37
  38 elements :: (Stack a) -> [a]
  39 elements s = s
  40
  41 Start  = ( "s0 = newStack = ",        s0,'\n'
  42          , "s1 = push 1 s0 = ",       s1,'\n'
  43          , "s2 = pushes [2..5] s1 = ",s2,'\n'
  44          , "s3 = pop s2 = ",          s3,'\n'
  45          , "s4 = popn 3 s3 = ",       s4,'\n'
  46          , "s5 = top s4 = ",          s5,'\n'
  47          , "s6 = topn 3 s2 = ",       s6,'\n'
  48          , "s7 = elements s2 = ",     s7,'\n'
  49 //       , "s8 = push 10 s1 = ",      s8,'\n'
  50 //       , "s9 = popn 10 s8 = ",      s9,'\n'
  51 //       , "sa = topn 5 s4 = ",       sa,'\n'
  52 //       , "sb = top s0 = ",          sb,'\n'
  53          )
  54 where
  55         s0 = newStack
  56         s1 = push 1 s0
  57         s2 = pushes [2..5] s1
  58         s3 = pop s2
  59         s4 = popn 3 s3
  60         s5 = top s4
  61         s6 = topn 3 s2
  62         s7 = elements s2
  63 //      s8 = push 10 s1
  64 //      s9 = popn 10 s8
  65 //      sa = topn 5 s4
  66 //      sb = top s0