(* Source code for lecture 2: Types *)


(* Bindings *)

type studentnumber = int
type name          = string
type class         = string
type grade         = char  

val id  : studentnumber
        = 200242
val joe : name
        = "Joe Smith"
val jc  : class
        = "CS201"
val jg  : grade
        = #"A"




(* Type of Intergers *)

  (* Values *)
  val pos10 : int 
            = 10
  val pos5  : int 
            = 5
  val neg42 : int 
            = ~42

  (* Operations *)
  val result1 : int
              = 10 + pos5
  val result2 : int
              = 5 * 4 * 3 * 2 * 1





(* Type of Reals *)

  (* Values *)
  val approxpi : real
               = 3.141

  (* Operations *)
  val result3  : real
               = Math.sin (approxpi / 2.0)





(* Type of Booleans *)

  (* Values *)
  val booltrue : bool
               = true

  (* Operations *) 
  val result4 : int
              = if 10 < 15 then 1 else ~1
  val result5 : bool
              = 12 < 15





(* Type of String *)
 
  (* Values *)
  val s1 = "Hello World"
  val s2 = "Computer Science"
  
  (*Operations*)
  val result6 : bool
              = s1 < s2






(* Type of functions *)

  (* Values *)
  val f1 : real -> real
         = fn x:real => (Math.sin x * Math.sin x) 
                       + (Math.cos x * Math.cos x)

  val f2 : string -> int
         = fn s:string => size s

  (* Operations *)
  val result7 : real
              = f1 10.0
  val result8 : int
              = f2 "Carsten"