(* Consider binary trees with integer values at the leaves, 
    and problems of 
    (i) summing these values,
    (ii) counting all nodes+leaves.

   Procedural solution  
*)

datatype tree =
  Node of tree * tree
| Leaf of int


fun sum t =
  case t of
    Node (l,r) => (sum l) + (sum r)
  | Leaf x => x

fun count t =
  case t of
    Node (l,r) => (count l) + (count r) + 1
  | Leaf x => 1

fun main() =
  let val t = Node(Leaf(1),Node(Leaf(2),Leaf(3)))
      val sum = sum t
      val count = count t
  in print ("Sum = " ^ (Int.toString sum) ^ "\n");
     print ("Count = " ^ (Int.toString count) ^ "\n")
  end