Definition

friend Nonmember Functions

A class give a nonmember function (or class) access to its nonpublic members by declaring it as a friend within its definition

• friend function is not a class member, but has access privileges as if it were
• friend functions are usually unnecessary if your class includes appropriate “getter” public functions

When to use nonmember and friend

• Member Functions:
  • Operators that modify the object being called on
    • Assignment operator (operator =)
  • “Core” non-operator functionality that is part of the class interface
• Nonmember Functions:
  • Used for commutative operators
    • e.g., so v1 + v2 is invoked as operators+(v1, v2) instead