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 "ifthenelse.hpp"
// primary template for main recursive step
template<int N, int LO=1, int HI=N>
class Sqrt {
public:
// compute the midpoint, rounded up
enum { mid = (LO+HI+1)/2 };
// search a not too large value in a halved interval
typedef typename IfThenElse<(N<mid*mid),
Sqrt<N,LO,mid-1>,
Sqrt<N,mid,HI> >::ResultT
SubT;
enum { result = SubT::result };
};
// partial specialization for end of recursion criterion
template<int N, int S>
class Sqrt<N, S, S> {
public:
enum { result = S };
};