程序代码：

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//coord.hpp

#include <cstdlib>

class Coord {
  private:
    int x, y;
  public:
    Coord (int i1, int i2) : x(i1), y(i2) {
    }
    friend Coord operator- (Coord const& c1, Coord const& c2) {
        return Coord(c1.x-c2.x, c1.y-c2.y);
    }
    Coord abs() {
        return Coord(std::abs(x),std::abs(y));
    }
};

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//dynahier.hpp
#include "coord.hpp"

// common abstract base class GeoObj for geometric objects
class GeoObj {
  public:
    // draw geometric object:
    virtual void draw() const = 0;
    // return center of gravity of geometric object:
    virtual Coord center_of_gravity() const = 0;
    //...
};

// concrete geometric object class Circle
// - derived from GeoObj
class Circle : public GeoObj {
  public:
    virtual void draw() const;
    virtual Coord center_of_gravity() const;
    //...
};

// concrete geometric object class Line
// - derived from GeoObj
class Line : public GeoObj {
  public:
    virtual void draw() const;
    virtual Coord center_of_gravity() const;
    //...
};
//...

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//dynapoly.cpp

#include "dynahier.hpp"
#include <vector>

// draw any GeoObj
void myDraw (GeoObj const& obj)
{
    obj.draw();            // call draw() according to type of object
}

// process distance of center of gravity between two GeoObjs
Coord distance (GeoObj const& x1, GeoObj const& x2)
{
    Coord c = x1.center_of_gravity() - x2.center_of_gravity();
    return c.abs();        // return coordinates as absolute values
}

// draw heterogeneous collection of GeoObjs
void drawElems (std::vector<GeoObj*> const& elems)
{
    for (unsigned i=0; i<elems.size(); ++i) {
        elems[i]->draw();  // call draw() according to type of element
    }
}

int main()
{
    Line l;
    Circle c, c1, c2;

    myDraw(l);            // myDraw(GeoObj&) => Line::draw()
    myDraw(c);            // myDraw(GeoObj&) => Circle::draw()

    distance(c1,c2);      // distance(GeoObj&,GeoObj&)
    distance(l,c);        // distance(GeoObj&,GeoObj&)

    std::vector<GeoObj*> coll;  // heterogeneous collection
    coll.push_back(&l);         // insert line
    coll.push_back(&c);         // insert circle
    drawElems(coll);            // draw different kinds of GeoObjs
}