C++ for Scientists - Technische Universität Dresden

7.5. FROM MONOMORPHIC TO POLYMORPHIC BEHAVIOR 215
class unstructured vertex : public vertex
{
public:
unstructured vertex(int handle, topology∗ topo, int segment) : handle(handle), segment(segment), topo(topo) {}
virtual bool equal(const vertex∗ ve) const
{
const unstructured vertex∗ sv = dynamic cast(ve);
return handle == (( sv→ handle ) && ( topo == sv→ topo) && (segment == sv→ segment));
}
protected:
int handle;
int segment;
topology∗ topo;
};
With this virtual class hierarchy, an algorithm which operates on all different classes derived
from vertex can be written. This is called explicit interface.
void print equal(const vertex∗ ve1, const vertex∗ ve2)
{
std::cout ≪ std::boolalpha ≪ ve1→ equal(ve2) ≪ std::endl;
}
The next code lines present the generic behavior of the algorithm, which operators on both
types derived from vertex.
int main()
{
topology the topo;
vertex∗ the vertex1;
vertex∗ the vertex2;
}
// ∗∗∗ structured
the vertex1 = new structured vertex(12, &the topo);
the vertex2 = new structured vertex(12, &the topo);
print equal(the vertex1, the vertex2);
// ∗∗∗ unstructured
the vertex1 = new unstructured vertex(12, &the topo, 1);
the vertex2 = new unstructured vertex(12, &the topo, 2);
print equal(the vertex1, the vertex2);
return 0;
As can be seen, polymorphic behavior can be achieved, but with major drawbacks. First,