CS 1MD3 - Winter 2006 - Assignment #2

Generated for Student ID: 0462082

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 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:
		theNorm = theNorm + abs(aVector[i])**2
		i=i+1
	return pow(theNorm, 0.5)

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 = -n 
	while i <= 0
		if list1[i] != list2[i]:
			distance = distance + 1
		i=i+1
	return distance

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

def isPalindrome(aList):
	"""Returns True if the list reads the same backwards and forwards."""
	n = len(aList)
	cursor = 1-n
	while cursor <= 0:
		if (aList[cursor] != aList[-cursor-1]):
			return False
		cursor=cursor-1	
	return True

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 indexOf(strg, sub):
	"""Returns the index of the first occurrence of the substring 'sub' within the string 'strg,' 
	or -1 if 'sub' isn't a substring of 'strg.'"""
	if len(sub) > len(strg):
		return -1
	index = 0
	foundIt = False
	while (index <= len(strg)-len(sub)) and (foundIt==False):
		i = 0
		while (i < len(sub)) and (strg[index+i] == sub[i]):
			i = i+1
		if i == len(sub):
			foundIt = True
		else:
			index = index + 1
	if foundIt == True:
		return index
	else:
		return -1