lec11prob5.py

# lec11prob5.py
#
# Lecture 11 - Classes
# Problem 5
#
# edX MITx 6.00.1x
# Introduction to Computer Science and Programming Using Python

'''
Consider the following code from the last lecture video.
Your task is to define the following two methods for the intSet class:

    1. Define an intersect method that returns a new intSet containing elements
    that appear in both sets. In other words,

        s1.intersect(s2)

    would return a new intSet of integers that appear in both s1 and s2. Think
    carefully - what should happen if s1 and s2 have no elements in common?


    2. Add the appropriate method(s) so that len(s) returns the number of
    elements in s.

    Hint: look through the Python docs to figure out what you'll need to solve
    this problem.

    http://docs.python.org/release/2.7.3/reference/datamodel.html
'''


class intSet(object):
    """An intSet is a set of integers
    The value is represented by a list of ints, self.vals.
    Each int in the set occurs in self.vals exactly once."""

    def __init__(self):
        """Create an empty set of integers"""
        self.vals = []

    def insert(self, e):
        """Assumes e is an integer and inserts e into self"""
        if not e in self.vals:
            self.vals.append(e)

    def member(self, e):
        """Assumes e is an integer
        Returns True if e is in self, and False otherwise"""
        return e in self.vals

    def remove(self, e):
        """Assumes e is an integer and removes e from self
        Raises ValueError if e is not in self"""
        try:
            self.vals.remove(e)
        except:
            raise ValueError(str(e) + ' not found')

    def __str__(self):
        """Returns a string representation of self"""
        self.vals.sort()
        return '{' + ','.join([str(e) for e in self.vals]) + '}'

    def intersect(self, other):
        """ Returns a new IntSet that contains of integers in both s1 & s2 """

        # create a new intSet
        commonVals = intSet()

        for x in self.vals:
            if other.member(x):
                commonVals.insert(x)
        return commonVals

    def __len__(self):
        return len(self)
        # return len(self.vals)



# s = intSet()
# print s
# s.insert(3)
# s.insert(4)
# s.insert(3)
# print s
# s.member(3)
# s.member(5)
# s.insert(6)
# print s
# s.remove(3)
# print s
# s.remove(3)