MCS-177 Homework 5, Fall 2005

Due: November 2, 2005

• Do exercise 5.15 on page 123.

• Exercise 5.x2: Suppose the following have been defined:

  (define make-shifted
    (lambda (shift-amount f)
      (lambda (x)
        (f (+ x shift-amount)))))
  
  (define double
    (lambda (x)
      (* x 2)))
  
  (define mystery
    (make-shifted 5 double))
  

  For each of the following expressions, indicate whether an error would be signaled, the value would be a procedure, or the value would be a number. If an error is signaled, explain briefly the nature of the error. If the value is a procedure, specify how many arguments the procedure expects. If the value is a number, specify which number.
  1. make-shifted
  2. mystery
  3. (mystery 4)
  4. (mystery double)
  5. ((make-shifted 3 double) 4)
  6. ((make-shifted 3 4) 5)
  7. (make-shifted 3 double)
  8. ((make-shifted 3 (make-shifted 4 double)) 5)

• Do exercise 5.8 on page 120.

• Exercise 6.x1: The following procedure is a modified version of the prompt procedure on page 142. Explain what the point of the modification is and give a concrete example (printed out from DrScheme) illustrating its use.

  (define prompt-for
    (lambda (prompt-string ok?)
      (newline)
      (display prompt-string)
      (newline)
      (let ((value (read)))
        (if (ok? value)
            value
            (prompt-for prompt-string ok?)))))
  

• Do exercise 6.24 on pages 162-163. Note that this exercise asks for a procedural representation, which is the sort illustrated on page 148.