Skip to Main Content
C++ Cookbook
book

C++ Cookbook

by D. Ryan Stephens, Christopher Diggins, Jonathan Turkanis, Jeff Cogswell
November 2005
Beginner to intermediate content levelBeginner to intermediate
594 pages
16h 23m
English
O'Reilly Media, Inc.
Content preview from C++ Cookbook

8.14. Overloading Arithmetic and Assignment Operators for Intuitive Class Behavior

Problem

You have a class for which some of C++’s unary or binary operators make sense, and you want users of your class to be able to use them when working with objects of your class. For example, if you have a class named Balance that contains, essentially, a floating-point value (i.e., an account balance), it would be convenient if you could use Balance objects with some standard C++ operators, like this:

Balance checking(50.0), savings(100.0);

checking += 12.0;
Balance total = checking + savings;

Solution

Overload the operators you want to use as member functions and standalone functions to allow arguments of various types for which the given operator makes sense, as in Example 8-15.

Example 8-15. Overloading unary and binary operators

#include <iostream> using namespace std; class Balance { // These have to see private data friend const Balance operator+(const Balance& lhs, const Balance& rhs); friend const Balance operator+(double lhs, const Balance& rhs); friend const Balance operator+(const Balance& lhs, double rhs); public: Balance() : val_(0.0) {} Balance(double val) : val_(val) {} ~Balance() {} // Unary operators Balance& operator+=(const Balance& other) { val_ += other.val_; return(*this); } Balance& operator+=(double other) { val_ += other; return(*this); } double getVal() const {return(val_);} private: double val_; }; // Binary operators const Balance operator+(const Balance& lhs, ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Start your free trial

You might also like

C++ System Programming Cookbook

C++ System Programming Cookbook

Onorato Vaticone

Publisher Resources

ISBN: 0596007612Supplemental ContentErrata Page