5  Exercise: Binding and Scope

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The purpose of this exercise is to warm up on the concepts of binding and scope, by example, in Scala.

For each the following uses of variable names, give the line where that name is bound. Briefly explain your reasoning (in no more than 1–2 sentences).

5.1 Example 1

Consider the following Scala code:

val pi = 3.14
def circumference(r: Double): Double = {
  val pi = 3.14159
  2.0 * pi * r
}
def area(r: Double): Double =
  pi * r * r

pi: Double = 3.14
defined function circumference
defined function area

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Exercise 5.1 The use of pi at line 4 is bound at which line? Briefly explain.

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Exercise 5.2 The use of pi at line 7 is bound at which line? Briefly explain.

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5.2 Example 2

Consider the following Scala code:

val x = 3
def f(x: Int): Int =
  x match {
    case 0 => 0
    case x => {
      val y = x + 1
      ({
        val x = y + 1
        y
      } * f(x - 1))
    }
  }
val y = x + f(x)

x: Int = 3
defined function f
y: Int = 3

Exercise 5.3 The use of x at line 3 is bound at which line? Briefly explain.

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Exercise 5.4 The use of x at line 6 is bound at which line? Briefly explain.

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Exercise 5.5 The use of x at line 10 is bound at which line? Briefly explain.

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Exercise 5.6 The uses of x at line 13 is bound at which line? Briefly explain.

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