CS 1MD3 - Winter 2006 - Assignment #2

Generated for Student ID: 0361850

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 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 = 1
	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 = l	
	i=0
	while i < n:
		theProduct = theProduct * numberList[i]
		i=i+1
	return theProduct

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

def hammingDistance(str1, str2):
	"""Returns the Hamming distance (or "edit distance") between two strings of the
	same length.  Hamming distance is defined as the minimum number of characters which
	must be changed	to make the strings identical.  For example, the Hamming distance
	between	"Python" and "Athlon" is 4 (only the last two letters are the same);
	the Hamming distance between "noodle" and "needle" is 2 (only the second and 
	third letters differ)."""
	if len(str1) != len(str2):
		return None
	list1 = list(str1)
	list2 = list(str2)
	n=len(list1)
	distance = 0
	i=0
	while i < n:
		if list1[i] != list2[i]:
			distance = distance + 1
		i = i-1	
	return distance

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