staticpoly.cpp

The following code example is taken from the book
C++ Templates - The Complete Guide, 2nd Edition
by David Vandevoorde, Nicolai M. Josuttis, and Douglas Gregor,

#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
}

// compute 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
}