A202/A598 Introduction to Programming II (4/3 cr.)

Spring Semester 2007

Homework Three: Classes and objects.

Consider the following code:

It should print the value of 5.

def test():
    a = point(3, 0)
    b = point(0, 4)
    print a.distanceTo(b)

Problem One:

Define a class of objects called point that model points in a plane:

A point is a pair of two coordinates (x and y).
Every point can calculate and report its distance to any other point;
the distance is the square root of the sum of the squared differences between the corresponding points' coordinates.

Now consider the following code:

This prints 5 (first) then the square root of 2.

def test():
    u = line(point(3, 0), point(0, 4))
    print u.length()
    v = line(point(-1, 0), point(0, -1))
    print v.length()

Problem Two:

Define a class of objects called line that models lines in 2D.

Every line is a pair of two points.
A point is a pair of two numbers as before.
points should be able to determine their distance to other points (see above).
lines are created by passing two points to the Line constructor.
A line object must be able to report its length;
the length of a line is the distance between its two end points.

Consider the following code:

It prints 6.0 (the area of the triangle).

def test():
    t = triangle(point(0, 3), point(0, 0), point(4, 0))
    print t.area()

Problem Three:

Define a class of objects called triangle that model planar triangles.

A triangle should be a set of three lines
However, a triangle is created by specifying three points
Every triangle should be able to calculate and report its area.
(If the three points are collinear the triangle is extremely flat, its area is 0 (zero), and that should be acceptable.)
Use Heron's formula to calculate the area of any triangle specified as above.

Consider the following code:

def test():
    c = clock("23:56")
    for i in range(10):
        c.tick()

It prints this:

>>> test()
23:57
23:58
23:59
00:00
00:01
00:02
00:03
00:04
00:05
00:06

Problem Four:

Define a class of objects called clock that models a clock.
Enough said.

Consider the following code:

def test():
    t = tigger(12, 34)
    for i in range(10):
        t.bounce()

It produces the following:

>>> test()
Tigger created at  ( 12,  34)
Tigger has just bounced to (  5,  25)
Tigger has just bounced to ( 25,  29)
Tigger has just bounced to ( 29,  85)
Tigger has just bounced to ( 85,  89)
Tigger has just bounced to ( 89, 145)
Tigger has just bounced to (145,  42)
Tigger has just bounced to ( 42,  20)
Tigger has just bounced to ( 20,   4)
Tigger has just bounced to (  4,  16)
Tigger has just bounced to ( 16,  37)
>>>

Problem Five:

Define a class of objects called tigger that can bounce().

tiggers are two-dimensional objects.
when they bounce their x and y coordinates change
the rule by which they change: they become the sum of the squares of their digits

For examples of the transformation rule see the sample run above.

The due date of this assignment will be announced shortly.

It will be something like Feb 7-9 or so.

An official due date will be posted soon on What's Due?

The date listed above is just a ballpark date, to help you plan.

Updated by Adrian German for A202/A598