C++ Primer, Fifth Edition

Assignment and Compound Assignment Operators

Assignment operators should behave analogously to the synthesized operators: After an assignment, the values in the left-hand and right-hand operands should have the same value, and the operator should return a reference to its left-hand operand. Overloaded assignment should generalize the built-in meaning of assignment, not circumvent it.

Caution: Use Operator Overloading Judiciously

Each operator has an associated meaning from its use on the built-in types. Binary +, for example, is strongly identified with addition. Mapping binary + to an analogous operation for a class type can provide a convenient notational shorthand. For example, the library string type, following a convention common to many ...