C++ Tutorial/template/Template specialization — различия между версиями

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Текущая версия на 10:30, 25 мая 2010

Partial specialization as end criteria

/* 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.
 */
#include <iostream>

// primary template
template <int DIM, typename T>
class DotProduct {
  public:
    static T result (T* a, T* b) {
        return *a * *b  +  DotProduct<DIM-1,T>::result(a+1,b+1);
    }
};
// partial specialization as end criteria
template <typename T>
class DotProduct<1,T> {
  public:
    static T result (T* a, T* b) {
        return *a * *b;
    }
};
// convenience function
template <int DIM, typename T>
inline T dot_product (T* a, T* b)
{
    return DotProduct<DIM,T>::result(a,b);
}
int main()
{
    int a[3] = { 1, 2, 3};
    int b[3] = { 5, 6, 7};
              << "\n";
              << "\n";
}
dot_product<3>(a,b) = 38
dot_product<3>(a,a) = 14

Primary template to compute 3 to the Nth and full specialization to end the recursion

/* 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.
 */
#include <iostream>

// primary template to compute 3 to the Nth
template<int N>
class Pow3 {
  public:
    enum { result = 3 * Pow3<N-1>::result };
};
// full specialization to end the recursion
template<>
class Pow3<0> {
  public:
    enum { result = 1 };
};
int main()
{
    std::cout << "Pow3<7>::result = " << Pow3<7>::result
              << "\n";
}
Pow3<7>::result = 2187

Template specialization

#include <iostream.h>
template <class T>
class MyClass {
    T value1, value2;
  public:
    MyClass (T first, T second)
      {value1=first; value2=second;}
    T module () {return 0;}
};
template <>
class MyClass <int> {
    int value1, value2;
  public:
    MyClass (int first, int second){
        value1 = first; 
        value2 = second;
    }
    int module (){
        return value1value2;
    }
};
int main () {
  MyClass <int> myints (100,75);
  MyClass <float> myfloats (100.0,75.0);
  cout << myints.module() << "\n";
  cout << myfloats.module() << "\n";
  return 0;
}
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Источник — «http://cppe.ru/index.php?title=C%2B%2B_Tutorial/template/Template_specialization&oldid=2602»