CS 1MD3 - Winter 2006 - Assignment #2

Generated for Student ID: 0563261

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

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 deinterlaceOdd(interlacedList):
	"""Returns a list consisting of only the odd elements of the given list.
	For example, deinterlaceOdd(['1', 'a', '2', 'b', '3', 'c']) returns [a,b,c]."""
	n = len(interlacedList)
	if n <= 1:
		return None
	i = 1
	oddList = []
	while i < n:
		oddList.append(interlacedlist[i])	
		i = i+2
	return oddList

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)

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