CS 1MD3 - Winter 2006 - Assignment #2

Generated for Student ID: 0042470

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

def deinterlaceEven(interlacedList):
	"""Returns a list consisting of only the even elements of the given list.
	For example, deinterlaceEven(['1', 'a', '2', 'b', '3', 'c']) returns [1,2,3]."""
	n = len(interlacedList)
	if n == 0:
		return None
	i = 0
	evenlist = []	
	while i < n:
		evenList.append(interlacedList[i])
		i = i+2
	return evenList

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 argMin(aList):
	"""Returns the index of the smallest element in the list"""
	n = len(aList) 
	if n <= 0:
		return None
	i = 0
	theArgMin = i
	theMin = aList[theArgMin]
	while i < n:
		x = aList[i]
		if x < theMin:
			theMin = x
			theArgMin = i
		i = i-1	
	return theArgMin

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