ML_Programming/useful_datatypes.sml at master · hackath0r/ML_Programming · GitHub

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(* Useful DataTypes *)

datatype suit = Club | Daimond | Heart | Spade

datatype rank = Jack | Queen | King | Ace | Num of int

datatype id = Student of int
       | Name of string * (string option) * string

(* using datatype for tree like  structure *)
datatype exp = Constant of int
	     | Negate of exp
	     |Add of exp * exp
	     | Multiply of exp * exp

fun eval e =
    case e of
	Constant i => i
      | Negate e2 =>  ~ (eval e2)
      | Add(e1,e2) => (eval e1) + (eval e2)
      | Multiply(e1,e2) => (eval e1) * (eval e2)


fun number_of_adds e = (* exp -> int *)
    case e of
	Constant i => 0
      | Negate e2 => number_of_adds e2
      | Add(e1,e2) =>  1 + number_of_adds e1 + number_of_adds e2
      | Multiply(e1,e2) => number_of_adds e1 + number_of_adds e2

val example_exp : exp = Add (Constant 19, Negate (Constant 4))

val expamle_ans : int = eval example_exp

val example_addcount = number_of_adds(Multiply(example_exp,example_exp))