sqrt1.hpp

C++ Templates 完全导引范例asics

/* The following code example is taken from the book
 * "C++ Templates - The Complete Guide"
 * by David Vandevoorde and Nicolai M. Josuttis, Addison-Wesley, 2002
 *
 * (C) Copyright David Vandevoorde and Nicolai M. Josuttis 2002.
 * Permission to copy, use, modify, sell and distribute this software
 * is granted provided this copyright notice appears in all copies.
 * This software is provided "as is" without express or implied
 * warranty, and with no claim as to its suitability for any purpose.
 */
#ifndef SQRT_HPP
#define SQRT_HPP

// primary template to compute sqrt(N)
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
    enum { result = (N<mid*mid) ? Sqrt<N,LO,mid-1>::result
                                : Sqrt<N,mid,HI>::result };
};

// partial specialization for the case when LO equals HI
template<int N, int M>
class Sqrt<N,M,M> {
  public:
    enum { result = M };
};

#endif // SQRT_HPP