C++ - 成员函数(member function)模板(template) 详解 及 代码

成员函数(member function)模板(template) 详解 及 代码

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成员模板(member template) 既可以在普通类(ordinary class), 也可以在类模板(class template);
在普通类中, 在使用成员函数时, 不用提供模板参数, 函数可以根据使用的参数,
自动推导(deduce)模板实参(template argument)对应模板形参(template parameter);
在类模板中, 成员函数的模板参数(template parameter)可以和类的模板参数不同, 但在定义(definition)中,
必须添加两个模板参数列表(template parameter list), 第一个为类的, 第二个为成员函数的;
代码如下:

/*   * cppprimer.cpp   *   *  Created on: 2013.11.24   *      Author: Caroline   */    /*eclipse cdt, gcc 4.8.1*/    #include <iostream>  #include <functional>  #include <memory>  #include <algorithm>  #include <string>  #include <vector>  #include <deque>  #include <iterator>    //函数模板默认参数  template <typename T, typename F = std::less<T>>  int compare (const T &v1, const T &v2, F f = F())  {  	if (f(v1, v2)) return -1;  	if (f(v2, v1)) return 1;  	return 0;  }    class DebugDelete {  public:  	DebugDelete (std::ostream &s = std::cerr) : os (s) { }  	template <typename T> void operator() (T *p) const {  		os << "deleting unique_ptr" << std::endl; delete p;  	}  private:  	std::ostream &os;  };    template <typename T> class Blob {  public:  	template <typename It> Blob (It b, It e);  	/*template <typename It> Blob (It b, It e) {  		std::sort(b, e);  	}*/  };    template <typename T>  template <typename It>  Blob<T>::Blob (It b, It e) {  		std::sort(b, e); //容器需要允许被排序  }    int main (void) {    	std::cout << "compare (0, 42) = " << compare (0, 42) << std::endl;    	double* p = new double;  	DebugDelete d;  	d(p); //使用时, 可以自动推倒模板  	int* ip = new int;  	DebugDelete() (ip);  	std::unique_ptr<int, DebugDelete> pi (new int, DebugDelete());  	std::unique_ptr<std::string, DebugDelete> ps (new std::string, DebugDelete());    	int ia[] = {9, 8, 7, 6, 5};  	std::vector<long> vi = {5, 4, 3, 2, 1, 0};  	std::deque<std::string> w = {"lady", "girl", "woman", "now"};    	Blob<int> a1(std::begin(ia), std::end(ia));  	Blob<int> a2(vi.begin(), vi.end());  	Blob<std::string> a3(w.begin(), w.end());    	std::cout << "int ia[] = ";  	for (const auto i : ia) { std::cout << i << " "; }  	std::cout << std::endl;  	std::cout << "std::vector<long> vi = ";  	for (const auto i : vi) { std::cout << i << " "; }  	std::cout << std::endl;  	std::cout << "std::list<const char*> w = ";  	for (const auto i : w) { std::cout << i << " "; }  	std::cout << std::endl;    	return 0;    }

输出:

deleting unique_ptr  deleting unique_ptr  deleting unique_ptr  deleting unique_ptr  compare (0, 42) = -1  int ia[] = 5 6 7 8 9   std::vector<long> vi = 0 1 2 3 4 5   std::list<const char*> w = girl lady now woman

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