Description

Pure Virtual Functions & Abstract Classes

An abstract class is a class with a virtual function declaration only, i.e., no function implementation. In the example of Lab 13-3, Shape has the virtual function output(). In many cases, we actually do not need to use any object of Shape class, since we either use Rectangle or Triangledirectly instead of Shape. Therefore, we do not need to implement the output() function for Shape. We can use the following function delcaration

virtual void output() = 0;

in Shape's class definition. This means there is no function implementation and therefore we cannot define an object of Shape class any more. output() is a pure virtual function and Shape is an abstract class.

What You Need to Do

1. In the class Shape: (1) modify output() to be a pure virtual function. (2) Define another pure virtual function area() which returns a double.
2. In the class Rectangle: (1) Add two protected data members: width and height, both are of type double. (2) Modify all member functions accordingly and implement area().
3. In the class Triangle: (1) Add two protected data members: base and height, both are of type double. (2) Modify all member functions accordingly and implement area().
4. Define another derived class Circle from Shape that has one protected data member radius of type double and three member functions output(), area(), and a constructor. Use the following macro for the constant π

#define PI 3.14159

main() is given. Do no make any changes, otherwise you may get penalty points.

int main() {
    double a, b;
    int x, y; // location of the shape
    string str;
    cin >> a >> b >> x >> y >> str;
    Rectangle rec(a, b, x, y, str);

    cin >> a >> b >> x >> y >> str;
    Triangle  tri(a, b, x, y, str);
    
    cin >> a >> x >> y >> str;
    Circle cir(a, x, y, str);
    
    // polymorphism using pointer
    Shape *ptr = &rec;
    ptr->output();
    cout << ptr->area() << endl;
    ptr = &tri;
    ptr->output();
    cout << ptr->area() << endl;

    // polymorphism using reference
    Shape &s1 = cir;
    s1.output();
    cout << s1.area() << endl;
    
    return 0;
}

Input

3.54 2.7 10 7 blue
8.22 7.14 10 5 black
7.333 64 3 green

Output

blue Rectangle at (10,7)
9.558
black Triangle at (10,5)
29.3454
green Circle at (64,3)
168.932

Sample Input  Download

Sample Output  Download

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Description

Templates and Generic Programing

You are going to implement a simple function GetMax that returns the bigger object of two. It works for any types/class that can be compared by a > or < operator. Check out function templates for its syntax.

main() is given. Do no make any changes, otherwise you may get penalty points.

int main () { // DO NOT CHANGE MAIN!!
    int i, j;
    double l, m;
    string s1, s2;
    cin >> i >> j >> l >> m >> s1 >> s2;
    cout << GetMax(i, j) << endl << GetMax(l, m) << endl
         << GetMax<string>(s1, s2) << endl;
    return 0;
}

Input

4 53 2.2 993.548 oh my!

Output

53
993.548
oh

Sample Input  Download

Sample Output  Download

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