C++模板

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原来...C++ template1.自定义Stack模板类#include <vector>#include <stdexcept>template <typename T>class Stack {  private:    std::vector<T> elems;     // elements  public:    void push(T const&);      // push element    void pop();               // pop element    T top() const;            // return top element    bool empty() const {      // return whether the stack is empty        return elems.empty();    }};template <typename T>void Stack<T>::push (T const& elem){    elems.push_back(elem);    // append copy of passed elem}template<typename T>void Stack<T>::pop (){    if (elems.empty()) {        throw std::out_of_range("Stack<>::pop(): empty stack");    }    elems.pop_back();         // remove last element}template <typename T>T Stack<T>::top () const{    if (elems.empty()) {        throw std::out_of_range("Stack<>::top(): empty stack");    }    return elems.back();      // return copy of last element}测试#include <iostream>#include <string>#include <cstdlib>#include "stack1.hpp"int main(){    try {        Stack<int>         intStack;       // stack of ints        Stack<std::string> stringStack;    // stack of strings        // manipulate int stack        intStack.push(7);        std::cout << intStack.top() << std::endl;        // manipulate string stack        stringStack.push("hello");        std::cout << stringStack.top() << std::endl;         stringStack.pop();        stringStack.pop();    }    catch (std::exception const& ex) {        std::cerr << "Exception: " << ex.what() << std::endl;        return EXIT_FAILURE;  // exit program with ERROR status    }}由于多掉了一次pop所以报错2.用typdef产生一个特定模板类别名比如Stack<int>typedef Stack<int> IntStack;int main(){    IntStack intStack;    intStack.push(7);    std::cout << intStack.top() << std::endl;}3.模板类的特化#include <deque>#include <string>#include <stdexcept>#include "stack1.hpp"template<>class Stack<std::string> {  private:    std::deque<std::string> elems;  // elements  public:    void push(std::string const&);  // push element    void pop();                     // pop element    std::string top() const;        // return top element    bool empty() const {            // return whether the stack is empty        return elems.empty();    }};void Stack<std::string>::push (std::string const& elem){    elems.push_back(elem);    // append copy of passed elem}void Stack<std::string>::pop (){    if (elems.empty()) {        throw std::out_of_range                ("Stack<std::string>::pop(): empty stack");    }    elems.pop_back();         // remove last element}std::string Stack<std::string>::top () const{    if (elems.empty()) {        throw std::out_of_range                ("Stack<std::string>::top(): empty stack");    }    return elems.back();      // return copy of last element}基于模板类之上，对于特定类型进行重新实现，比如上面就是一个对std:: string的特例实现,内部用deque实现测试#include <iostream>#include <string>#include <cstdlib>#include "stack2.hpp"int main(){    try {        Stack<int>         intStack;       // stack of ints        Stack<std::string> stringStack;    // stack of strings        // manipulate int stack        intStack.push(7);        std::cout << intStack.top() << std::endl;        intStack.pop();        // manipulate string stack        stringStack.push("hello");        std::cout << stringStack.top() << std::endl;         stringStack.pop();        stringStack.pop();    }    catch (std::exception const& ex) {        std::cerr << "Exception: " << ex.what() << std::endl;        return EXIT_FAILURE;  // exit program with ERROR status    }}上面Stack<std::string>使用了特化的类4.局部特化若模板类有两个参数，那么确定其中一个参数,另一个未确定的话，则可以说是局部特化template <typename T1, typename T2>class MyClass {...};//偏特化：两个template parameter相同template <typename T>class MyClass<T, T> {...};//偏特化：第二个参数为inttemplate <typename T>class MyClass<T, int> {...};这些概念与c#的泛型是相同的.5.预设模板与局部特化概念差不多,但保留了参数，给参数设置了一个默认的类型#include <vector>#include <stdexcept>template <typename T, typename CONT = std::vector<T> >class Stack {  private:    CONT elems;               // elements  public:    void push(T const&);      // push element    void pop();               // pop element    T top() const;            // return top element    bool empty() const {      // return whether the stack is empty        return elems.empty();    }};template <typename T, typename CONT>void Stack<T,CONT>::push (T const& elem){    elems.push_back(elem);    // append copy of passed elem}template <typename T, typename CONT>void Stack<T,CONT>::pop (){    if (elems.empty()) {        throw std::out_of_range("Stack<>::pop(): empty stack");    }    elems.pop_back();         // remove last element}template <typename T, typename CONT>T Stack<T,CONT>::top () const{    if (elems.empty()) {        throw std::out_of_range("Stack<>::top(): empty stack");    }    return elems.back();      // return copy of last element}示例:这样如果用默认的类型，就可以少指定一个模板类的类型#include <iostream>#include <deque>#include <cstdlib>#include "stack3.hpp"int main(){    try {        // stack of ints:        Stack<int> intStack;        // stack of doubles which uses a std::deque<> to manage the elements        Stack<double,std::deque<double> > dblStack;        // manipulate int stack        intStack.push(7);        std::cout << intStack.top() << std::endl;        intStack.pop();        // manipulate double stack        dblStack.push(42.42);        std::cout << dblStack.top() << std::endl;         dblStack.pop();        dblStack.pop();    }    catch (std::exception const& ex) {        std::cerr << "Exception: " << ex.what() << std::endl;        return EXIT_FAILURE;  // exit program with ERROR status    }}
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