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Overloading +
OO in C++ - beyond the basics example from a Well House Consultants training course
More on OO in C++ - beyond the basics [link]
Source code: shapes_03.cpp Module: C233
#include <iostream>
using namespace std; /* An extension of the demonstration of a polymorphic array of various types of shape on the heap, adding in addition opeators showing how we can overload "+" for one / each of our object types. The demonstration also defines a method called "add" on Circles, which illustrates what's really going on in the method definition for "+", and then calls it up using the standard OO notation rather than the icing provided by the use of the language's operator. */ class Shape { public: float width; float height; // bool cached; Later ;-) virtual float getarea() {} ; }; class Circle: public Shape { public: Circle(float radius); float getarea() ; Circle operator+(Circle); Circle add(Circle); }; class Rectangle: public Shape { public: Rectangle(float width, float height); float getarea() ; }; class Square: public Rectangle { public: Square(float size); }; Square::Square (float size) : Rectangle(size, size) { } Rectangle::Rectangle(float width, float height) { this->width = width; this->height = height; } Circle::Circle (float radius) { this->width = this->height = radius * 2.0; } float Circle::getarea() { return width * width * 3.14159265 / 4.0; } float Rectangle::getarea() { return width * height ; } Circle Circle::operator+(Circle that) { return(Circle((this->width + that.width)/2.0)); } Circle Circle::add(Circle that) { return(Circle((this->width + that.width)/2.0)); } int main (int argc, char **argv) { Shape * papers[5]; // Put the objects on the heap papers[0] = new Circle(15.0); papers[1] = new Rectangle(34.0,2.0); papers[2] = new Circle(2.3) ; papers[3] = new Square(3.33); papers[4] = new Rectangle(5.61,7.92); for (int k=0; k<5; k++) { Shape * current = papers[k]; cout << "Area is " << current->getarea() << endl; } Circle * left = new Circle(12.5); Circle * right = new Circle(16.6); // Circle all = (*left).operator+(*right); // Above is a nasty thing to try to write, so ... Circle all = *left + *right; cout << "ADDED to get " << all.getarea() << endl; // Same thing ... with an "add" method rather than operator+ Circle eall = (*left).add(*right); cout << "ADDED to get " << eall.getarea() << endl; } /* Sample Output munchkin:c5 grahamellis$ ./shapes_03 Area is 706.858 Area is 68 Area is 16.619 Area is 11.0889 Area is 44.4312 ADDED to get 2660.33 ADDED to get 2660.33 munchkin:c5 grahamellis$ */ Learn about this subject
This module and example are covered on the following public courses:
* Learning to program in C and C++ * C++ for C Programmers * C and C++ Programming * Learning to program in C and C++ * C and C++ Programming Also available on on site courses for larger groups Books covering this topic
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