c++类模板

一、类模板

T可以作为标识符，typename可以用class。

#ifndef STACK1_HPP
#define STACK1_HPP

#include <vector>
#include <stdexcept>

template<typename T>
class Stack {
private:
    std::vector<T> elems;
public:
    void push(T const &);
    void pop();
    T top() const;
    bool empty() const {
        return elems.empty();
    }
};

template<typename T>
void Stack<T>::push(T const& elem)
{
    elems.push_back(elem);
}

template<typename T>
void Stack<T>::pop()
{
    if(elems.empty()) {
        throw std::out_of_range("Stack<>::pop(): empty stack");
    }
    elems.pop_back();
}

template<typename T>
T Stack<T>::top() const
{
    if(elems.empty()) {
        throw std::out_of_range("Stack<>::top(): empty stack");
    }
    return elems.back();
}


#endif // STACK1_HPP

测试用例：

#include <iostream>
#include <string>
#include <cstdlib>
#include "stack1.hpp"

int runTest()
{
    try {
        Stack<int> intStack;
        Stack<std::string> stringStack;
        intStack.push(7);
        std::cout<<intStack.top()<<std::endl;

        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;
    }
}

二、类模板的特例化

#ifndef STACK2_HPP
#define STACK2_HPP

#include <deque>
#include <string>
#include <stdexcept>
#include "stack1.hpp"

template<>
class Stack<std::string> {
private:
    std::deque<std::string> elems;
public:
    void push(std::string const &elem);
    void pop();
    std::string top() const;
    bool empty() const {
        return elems.empty();
    }
};

void Stack<std::string>::push(const std::string &elem)
{
    elems.push_back(elem);
}

void Stack<std::string>::pop()
{
    if(elems.empty()) {
        throw std::out_of_range("Stack<std::string>::pop(): empty stack");
    }
    elems.pop_back();
}

std::string Stack<std::string>::top() const
{
    if(elems.empty()) {
        throw std::out_of_range("Stack<std::string>::top(): empty stack");
    }
    return elems.back();
}


#endif // STACK2_HPP

三、缺省模板实参

#ifndef STACK3_HPP
#define STACK3_HPP

#include <vector>
#include <stdexcept>

template <typename T, typename CONT = std::vector<T> >
class Stack {
private:
    CONT elems;
public:
    void push(T const &elem);
    void pop();
    T top() const;
    bool empty() const {
        return elems.empty();
    }
};

template <typename T, typename CONT>
void Stack<T,CONT>::push(const T &elem)
{
    elems.push_back(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();
}

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();
}

#endif // STACK3_HPP

测试用例：

int runTest3()
{
    try {
        Stack<int> intStack;
        Stack<double, std::deque<double> > dblStack;

        intStack.push(7);
        std::cout<<intStack.top()<<std::endl;

        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;
    }
}