Polymorphism without Inheritance

The num_sequence class of Section 4.10 simulates polymorphism. Each class object can be made

into any of the six numerical sequences at any point in the program through the set_sequence()

member function:

The ability to change the sequence type of ns is supported through programming rather than

through direct support of the language. Each class object contains an _isa data member that

identifies the current numeric sequence that it represents:

Running Codes

for (int ix = 1; ix < num_sequence::num_of_sequences(); ++ix)

{

ns.set_sequence(num_sequence::nstype(ix));

int elem_val = ns.elem(pos);

// ...

}

class num_sequence {

public:

// ...

private:

vector *_elem; // addresses current element vector

PtrType _pmf; // addresses current element generator

ns_type _isa; // identifies current sequence type

// ...

};