CS 1MD3 - Winter 2006 - Assignment #2

Generated for Student ID: 0461992

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

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)

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
	return theArgMin

 def isPalindrome(aList):
	"""Returns True if the list reads the same backwards and forwards."""
	n = len(aList)
	cursor = O	
	while cursor < n:
		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 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