3.2. Binary operations overload

Any binary operation Å can be defined in two ways: either as a component function with one parameter, or as a global (possibly friendly) function with two parameters. In the first case, x Å y means calling x.operator Å (y) , in the second case - calling operator Å (x, y).

· Operations overloaded within a class can only be overloaded with non-static component functions with parameters. The called class object is automatically taken as the first operand.

· Operations that are reloaded outside the scope of a class must have two operands, one of which must have a class type.

Examples

1) class person {...};

class adresbook

{// contains as component data a set of objects of type // person, represented as a dynamic array, list or tree

...

public:

person & operator [] (int); // access to the i-th object

};

person & adresbook:: operator [] (int i) {. . .}

void main ()

{class adresbook persons;

class person record;

...

record = persons [3];

}

2) class person {...};

class adresbook

{// contains as component data a set of objects of type // person, represented as a dynamic array, list or tree

...

public:

friend person & operator [] (const adresbook &, int); // access to the i-th object

};

person & operator [] (const adresbook & ob, int i) {. . .}

void main ()

{class adresbook persons;

class person record;

...

record = persons [3];

}