CS 1MD3 - Winter 2006 - Assignment #2

Generated for Student ID: 0550969

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 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

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 = n 
	while i >= n/2:
		j = n-i-1
		temp = aList[i]
		aList[i] = aList[j]
		aList[j] = temp
		i = i-1

def norm(aVector):
	"""Computes the Euclidian norm of the given vector in R^n.
	The Euclidean norm of x=(x1, x2, ..., xn) is defined as the square root of
	x1^2 + x2^2 + ... + xn^2."""
	n = len(aVector)
	if n <= 0:
		return None
	theNorm = 0
	i = 0
	while i < n:
		theNorn = theNorm + abs(aVector[i])**2	
		i=i+1
	return pow(theNorm, 0.5)

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
	return theArgMax

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 gcd(intList):
	"""Finds the greatest common divisor among the list elements (in an inefficient way)."""
	if len(intList) == 0:
		return None
	isDivisor = False
	divider = 0
	listMin = min(intList)
	candidate = 1
	while isDivisor == False:
		divider = divider + 1
		if listMin != divider * (listMin / divider): # if divider isn't a factor of listMin...
			continue
		candidate = listMin / divider
		isDivisor = True
		for x in intList:
			if x != candidate * (x / candidate):
				isDivisor = False
				break
	return candidate