CS 202留学生辅导、讲解Java程序、辅导Programming Systems、讲解Java编程

Programming Assignment #3

CS 202 Programming Systems

***This program is about operator overloading ***

Primary Goal for program #3:

The primary goal for program #3 is to experience operator overloading in an object

oriented environment. We want to correctly create classes that properly support

the copy constructor, destructor, and now the assignment operator when dynamic

memory is involved. Remember that copy constructors in a hierarchy require the

use of initialization lists to cause the base class copy constructor to be invoked.

Every class that manages dynamic memory must have a copy constructor,

destructor, and assignment operator.

Your primary goal with program #3 is to apply the functionality of the operators,

the appropriate arguments (operand data types) and returned types (residual

values for the operators) to the following problem. Think about how the operators

are used and try to mimic the behavior in your own classes. How is the returned

type used? Who controls the memory of the residual value? The client program

(lvalue) or the operator (rvalue). Make sure to pass (and return) by reference

whenever possible!

Remember OOP:

With OOP the key idea is to break down the problem outlined (below) into small

pieces and assign those responsibilities to individual classes. For each assignment,

your job will be to create an OO design and program that shows how Object

Oriented constructs could be used to solve a real-world problem. You will want to

focus on how to design classes that are well structured, efficient, that work

together, and where each class has a specific “job”. This time you are adding

operator overloading as the new syntax for your solution!

Before you design this program, take a look back at your first two programs. Did

you tie the data structures into the midst of your OO designs? Did the designs

really become all about the data structure and not so much about the problem at

hand? The key to OOP in my opinion is to create the design based on the problem

prior to applying the data structure. The data structures are about how we handle

the data – not necessarily the key to OOP. For this assignment, your application

will be the OOP portion of the assignment. Then, implement the data structures.

CS201 Fall 2018 Program #3

Program #3 – The Problem

We are entering the holiday season. Do you like to get together with friends or

family members? My sister always puts on some great feasts for us. Of course

many of us need to consider what foods we can or should actually eat. Are there

nuts? Gluten? Are there non-alcoholic choices for beverages? Many of us have

dietary restrictions needing gluten free, or needing to know about the contents of

nuts as well as many others. We also might need to select dishes based on their

known caloric or sugar values (it is not a pretty sight when my family has too

much sugar!). So, we want to develop an application that will allow a host to

communicate to others what options are available.

The Data: Your job for program #3 is to create a Food data type that allows users

to enter in specifics about that item in terms of common dietary restrictions. You

are to support at least three different types of food items that are similar yet

different (e.g., main_course, desert, beverages, etc.); the three types may be of your

selection but they should have similar but yet different characteristics. At least two

of your classes must support dynamically allocated data as part of the class (e.g.,

the name as a char *). Please have fun with these cclasses and come up with some

of your own characteristics.

Making it OO: We will use this concept to develop an OO application. You will

want to develop at least five classes, as normal. Make sure to use single inheritance

in your design. To break down the problem, think about what is similar or

different about different kinds of food characteristics. Use inheritance to push up

the common elements to the base class! Then, have the derived classes handle the

differences. Remember to avoid getters as much as possible with these classes –

instead implement the functions that actually work ON the data IN the classes that

own the data!! This is where you will get the most benefit of OOP.

Searching and the Data structure: Our data structure will be a TREE of food items

that are part of the hosts planned menu. You have an option with this – the TREE

can either be implemented as a Binary Search Tree (BST) or it can be implemented

as a 2-3-4 balanced tree. If you select a BST, then a balanced tree will be assigned

to you for Program #4 (in Java). *** If you are implementing a balanced tree, you

will not be expected to implement an individual removal operation (we will not

be removing individual characteristics in a balanced tree!). You can have three

different data structures for the three different types of food, or you may use dynamic

binding with upcasting, using just one data structure.

CS201 Fall 2018 Program #3

Operator Overloading: The key part of this assignment is to implement a complete

set of operators. The operators to support must include: =, +, +=, ==, !=, the

relational/equality operators, and the ability to input/output data. I imagine the []

would be useful as well for searching for a match. As you decide how to apply the

operators, make sure to stay within the rules of how the operators are expected to

behave.

All of the aforementioned operators NEED to be implemented. But, they do not

need to be implemented in the same class. OPERATORS DO NOT COUNT if

they are only implemented for a ‘string-like’ class. Although you MAY write

your own STRING data type, it can’t be the only place you use operator

overloading (since the code is in topic #6!).

Of course, the = operator needs to be implemented in all classes that manage

dynamic memory – and don’t forget your copy constructors!!!!

Questions to ask…about operator overloading

When using operator overloading, remember to ask yourself the following

questions:

a) What should be the residual value (and what data type is this)?

- Never have a void returning operator!

b) Should the result be a modifiable lvalue or an rvalue?

- Lvalues are returned by reference, most rvalues are returned by value.

c) What are the data types of the operator’s operands?

- If the operand isn’t changed, then make it a const

- Remember to pass as a constant reference whenever possible.

d) Is the first operand always an object of class?

- If so, then it could be a member function.

e) Can the operator be used with constant operands?

- If the first operand can be a constant, and IF it is a member function, then

it should be a constant member function.