#!/usr/bin/env python

# -*- coding:utf-8 -*-

# Author:Lijunjie

"""

File: baginterface.py

Author: Lijunjie

"""

class BagInterface( object ):

    """Interface for all bag types."""

    #Constructor

    def __init__( self, sourceCollection = None ):

        """Sets the initial state of self, which includes the contents

        of sourceCollection, if it's present."""

        pass

    #Accessor methods

    def isEmpty( self ):

        """Return True if len( self ) == 0, or False otherwise."""

        return True

    def __len__( self ):

        """Returns the number of items in self."""

        return 0

    def __str__( self ):

        """Return the string representation of self."""

        return ""

    def __iter__( self ):

        """Supports iteration over a view of self."""

        return None

    def __add__( self, other ):

        """Return a new bag containing the contents of self and other"""

        return None

    def __eq__( self, other ):

        """Return True if self equals other, otherwise False."""

        return False

    #Mutator methods

    def clear( self ):

        """Makes self become empty."""

        pass

    def add( self, item ):

        """Adds item to self."""

        pass

    def remove( self, item ):

        """

        Precondition: item is in self.

        Raise: KeyError if item is not in self.

        Postcondition: item is removed form self.

        """

        pass

#!/usr/bin/env python

# -*- coding:utf-8 -*-

# Author:Lijunjie

"""

File: arraybag.py

Author: Lijunjie

"""

from arrays import Array

class ArrayBag( object ):

    """An array-based bag implementation."""

    #Class variable

    DEFAULT_CAPACTIY = 10

    #Constructor

    def __init__( self, sourceCollection = None ):

        """Sets the initial state of self, which includes the contents

        of sourceCollection, if it's present."""

        self._items = Array( ArrayBag.DEFAULT_CAPACTIY )

        self._size = 0

        if sourceCollection:

            for item in sourceCollection:

                self.add( item )