The George Washington University
School of Engineering and Applied Science
Department of Computer Science
CSci 169 – Software Paradigms – Fall 2007
Homework #4
Due Date: Monday, December 3, 2007
Instructor: A. Bellaachia
Problem 1: (20 points)
Do problem 2 on page 330 of your textbook.
Problem 2: (20 points)
Do problem 3 on page 330 of your textbook.
Problem 3: (20 points)
The Scheme function reverse described in the lecture reverses only the “top level” of a list:
If L =((2 3) 4 (5 6)) then (reverse L) will return ((5 6) 4 (2 3)). Write a Scheme function
deep-reverse that also reverses all sub-lists: (deep-reverse L) will return ((( 6 5) 4 (3 2)).
Problem 4: (20 points)
What does the following scheme function do? Explain.
(define (mystery toto)
(cond ((null? toto) 0)
((not (list? (car toto)))
(cond ((eq? (car toto) '()) (mystery (cdr toto)))
(else (+ 1 (mystery (cdr toto))))))
(else ( + (mystery (car toto)) (mystery (cdr toto))))))
Problem 5: (20 points)
Write a Scheme function that tests for the structural equality of two given lists.
Two lists are structurally equal if they have the same list structure, although their
atoms may be different.