The following code example is taken from the book
C++ Templates - The Complete Guide
by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
© Copyright David Vandevoorde and Nicolai M. Josuttis 2002
#include "statichier.hpp"
#include <vector>
// draw any GeoObj
template <typename GeoObj>
void myDraw (GeoObj const& obj)
{
obj.draw(); // call draw() according to type of object
}
// process distance of center of gravity between two GeoObjs
template <typename GeoObj1, typename GeoObj2>
Coord distance (GeoObj1 const& x1, GeoObj2 const& x2)
{
Coord c = x1.center_of_gravity() - x2.center_of_gravity();
return c.abs(); // return coordinates as absolute values
}
// draw homogeneous collection of GeoObjs
template <typename GeoObj>
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<Line>(GeoObj&) => Line::draw()
myDraw(c); // myDraw<Circle>(GeoObj&) => Circle::draw()
distance(c1,c2); // distance<Circle,Circle>(GeoObj1&,GeoObj2&)
distance(l,c); // distance<Line,Circle>(GeoObj1&,GeoObj2&)
// std::vector<GeoObj*> coll; // ERROR: no heterogeneous
// collection possible
std::vector<Line> coll; // OK: homogeneous collection possible
coll.push_back(l); // insert line
drawElems(coll); // draw all lines
}