CS 1MD3 - Winter 2006 - Assignment #2

Generated for Student ID: 0568063

Due Date: Wednesday, February 8th

(You are responsible for verifying that your student number is correct!)

Part 1: Debugging

The following four functions are infested with bugs. Correct them by adding or changing a single line in each one. Clearly indicate your changes with comments. If you add a line, append the comment, "# added." If you change a line, append a comment to it containing the original, erroneous line. Solutions submitted without comments will not be marked.

1

def reverseList(aList):
	"""Reverses the elements of a list.  Yes, yes... Python has a built-in function
	to do that, but what if someone steals it?  Ha!  Bet you never thought of that,
	did ya??"""
	n = len(aList)
	i = 0
	while i < n/2:
	j = -i-1	
		temp = aList[i]
		aList[i] = aList[j]
		aList[j] = temp
		i = i+1

def argMax(aList):
	"""Returns the index of the largest element in the list"""
	n = len(aList) 
	if n <= 0:
		return None
	i = n-1
	theArgMax = i
	theMax = aList[theArgMax]
	while i > 0: 
		x = aList[i]
		if x > theMax:
			theMax = x
			theArgMax = i
		i = i - 1
	return theArgMax

def mean(numberList):
	"""Returns the mean (i.e. average) value of the elements in the list"""
	n = len(numberList)
	if n == 0:
		return None
	theSum = 0
	i = 0
	while i < n:
		x = NumberList[i]
		theSum = theSum + x
		i = i + 1
	return float(theSum) / float(n)

def product(numberList):
	"""Computes the product of all the list elements."""
	n = len(numberList)
	if n <= 0:
		return None
	theProduct = 1
	i = 0
	while i < n: 
		theProduct = theProduct * numberList[i]
		i=i+1
	return theProduct

Part 2: Testing

Create automated tests for the following function using PyUnit. Your tests should ensure that the code produces the expected result in all cases.

def isIsosceles(pt1, pt2, pt3):
	"""Accepts three lists of floating point numbers, each list specifying a point in
	(real) n-dimensional space.  Returns True if the three points are the corners of an
	isosceles triangle; returns False otherwise."""
	n = len(pt1)
	if len(pt2) != n or len(pt3) != n:
		return False
	edge1sqrd, edge2sqrd, edge3sqrd = 0, 0, 0
	for x,y in zip(pt1,pt2):
		edge1sqrd = edge1sqrd + (x-y)**2
	for x,y in zip(pt1,pt3):
		edge2sqrd = edge2sqrd + (x-y)**2
	for x,y in zip(pt2,pt3):
		edge3sqrd = edge3sqrd + (x-y)**2
	if edge1sqrd==edge2sqrd==edge3sqrd:	# We'll adopt the convention that equilateral ==> not isosceles
		return False
	if edge1sqrd==edge2sqrd or edge1sqrd==edge3sqrd or edge2sqrd==edge3sqrd:
		return True
	else:
		return False