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

 
本文地址: http://blog.csdn.net/caroline_wendy/article/details/16918085
 
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