Lecture Notes on 11 Sep 2020

def test_cases ():
  assert encrypt ('a') == 'a'
  assert encrypt ('ab') == 'ab'
  assert encrypt ('abc') == 'cab'
  assert encrypt ('abcd') == 'cadb'

import math

class Point (object):
  # constructor
  def __init__ (self, x = 0, y = 0):
    self.x = x
    self.y = y

  # get the distance to another Point object
  def dist (self, other):
    return math.hypot (self.x - other.x, self.y - other.y)

  # string representation of a Point
  def __str__ (self):
    return '(' + str(self.x) + ', ' + str(self.y) + ')'

  # test for equality of two Point objects
  def __eq__ (self, other):
    tol = 1.0e-6
    return ((abs(self.x - other.x) < tol) and (abs(self.y - other.y) < tol))

class Circle (object):
  # constructor 
  def __init__ (self, radius = 1, x = 0, y = 0):
    self.radius = radius
    self.center = Point (x, y)

  # compute the circumference
  def circumference (self):
    return 2 * math.pi * self.radius

  # compute the area
  def area (self):
    return math.pi * self.radius * self.radius

  # determine if a Point p is strictly inside the circle
  def point_inside (self, p):
    return self.center.dist(p) < self.radius

  # determine if a Circle c is strictly inside this circle
  def circle_inside (self, c):
    dist_centers = self.center.dist (c.center)
    return (dist_centers + c.radius) < self.radius

  # determine if a Circle c intersects this circle
  # Circle c has non-zero area inside and 
  # non-zero area outside this circle
  def circle_intersects (self, c):
    dist_centers = self.center.dist (c.center)
    is_inside = (dist_centers + c.radius) < self.radius
    is_outside = dist_centers > (self.radius + c.radius)
    return (not is_inside) and (not is_outside)

def main():

  # create Point objects
  a = Point (3, 4)
  b = Point (3, 4)

  # print the Point objects
  print (a)
  print (b)

  # get distances
  print (a.dist(b))
  print (b.dist(a))

  # test for equality
  print (a == b)

main()