1. operators are functions - accept two arguments and return a value

2. int plus(int, int) { . . .} - binary function

3. int negative(int) { . . . } - unary function

1. the syntax is a bit odd, requiring the keyword operator

2. for example bool operator == (hand h1, hand h2) { . . . }

3. the number of operators must match the standard use

   1. wrong - bool operator == (hand h1, hand h2, hand h3) { . . }

4. the types of the arguments may be different, as can the return value

   1. example double operator == (hand h1, int i) { . . . }

   2. fooling with the return value is bad programming

5. one of the argument types must be a class

   1. wrong - int operator / (int i, int j) { . . . }

6. there's two ways to call operator functions

   1. the operator way - hand h1, h2; if (h1 == h2) { . . . }

   2. the function way - hand h1, h2; if (operator ==(h1, h2) { . . . }

7. not all operators can be overloaded - the dot operator

1. the syntax is the same, except for the implicit argument

   1. for example - bool operator == (hand h) { . . . }

2. the calling syntax is the same

   1. the operator way - hand h1, h2; if (h1 == h2) { . . . }

   2. the function way - hand h1, h2; if (h1.operator ==(h2) { . . . }

3. operator overloading is sometimes handy, but

   1. used improperly it can make code difficult to understand

   2. it interacts in strange, subtle, and unfortunate ways with other c++ features

   3. defining overloaded operators correctly requires a lot of work

This page last modified on 25 June 2001.