CS21: Quiz 3 Study Guide

In addition to the concepts from Quiz 1 and Quiz 2,

You should be able to define the following terms:

object oriented programming
class
instance of a class
data and methods of an object
animation
function parameter
arguments
function definition
function call
call stack
scope of a variable

You should understand how to make instances of the following graphics library classes and how to use their methods:

GraphWin: getMouse()
Point: getX(), getY()
Line: getP1(), getP2()
Circle: getCenter(), getRadius()
Rectangle: getP1(), getP2()
Graphical objects can also: draw(window), undraw(), and move(dx, dy)

Practice problems:

Write a main program that draws a circle centered in the graphics window with a radius of 100 and draws a line vertically from the top of the graphics window to the bottom. The program should wait for a mouse click to end.
Multiple choice problems 1-5, pg. 192
Discussion problems 1-5, pg. 193
Write a function called avgList that takes a list of numbers as input and returns their average. For example, avgList([5, 10, 5, 4]) should return 6. Write a main program to test the function.
Write a function called maxList that takes a list of numbers as input and returns the largest number in the list. For example, maxList([7,4,8,1]) should return 8. Write a main program to test the function.

Consider the following program.

def main():
    print "in main"
    test = "whee"
    check = "e"
    answer = helper(test, check)
    print "the answer is", answer

def helper(word, letter):
    print "in helper"
    print "word:", word
    print "letter:", letter
    x = 0
    for ch in word:
        if ch == letter:
            x = x+1
    # draw stack here
    return x

main()

Draw the call stack as it would look just prior to returning from helper.
What is the program's output (i.e. what is printed when the program is run)?
What does the helper funciton compute?
What would helper("moobaalalala", "a") return?
What would helper("zoo", "a") return?

What would be the TYPE of each of these?

   p = Point(100,200)             type of p?
   c = Circle(p, 5)               type of c?
   x = c.getRadius()              type of x?
   c2 = Circle(p, 20)             type of c2?
   L = [c, c2]                    type of L?
   m = L[0]                       type of m?
   y = L[1].getCenter().getY()    type of y?
   answer = helper(test, check)   type of test?  type of answer (from above code)?