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SML Basics Examples

By Eunice Chen, May 2020

Types​

For each of the following declarations, state the type and value of x.

val x = 1 > 5
val x = 15 div 0
val x = 15.0 div 0.0
val x = fn (n : int) => Int.toString n
val x = fn n => ("1" ^ "5") ^ (Int.toString n)

Scope​

Example 0​

let
  val y : int = 2
in
  fn (x : int) => z*z
end

What is the value of the let-in-end expression?

Example 1​

val y = 0
val z =
    (let
      val x : int = 1
      fun f (x : int) = x
      val y : int = x + 1
    in
      fn (a : string) => x*2
    end) "150"
val a = y

What is the value of y before the let-in-end expression?

What is the value of y within the let-in-end expression?

What is the value of a?

What is the value of z?

Example 2​

val x : int = 1
fun f (x : int) = x + 1
val y : int = 2
val z : int = f y
val a : int = x

What are the values of x, y, z, and a?

Example 3​

val x = 1
val y = 2
fun f (x, y) =
    case x of
      0 => 0
    | y => y
val a = f (y, x)
val b = f (x, y)

What are the values of a and b?