类模板

示例 加法

类外实现函数时，必须使用显示指定模板

#include<iostream>
using namespace std;
template<class T>
class A {
private:
    T first;
    T second;
public:
    A(T a, T b): first(a), second(b) {};
    void add();
};
template<class T>
void A<T>::add() {
    cout << first + second<<endl;
}
void testA() {
    A<int> a(1, 2);
    a.add();
    A<double> b(2.5,3);
    b.add();
}
int main() {
    testA();
}

示例2 封装Stack

#include<iostream>
#include<vector>
using namespace std;
template<class T>
class Stack {
private:
    vector<T> elems;
public:
    void push(T const&);
    void pop();
    T top() const;
    bool empty() const { return elems.empty(); }
};
template<class T>
void Stack<T>::push(T const& elem) {
    elems.push_back(elem);
}
template<class T>
void Stack<T>::pop() {
    if (elems.empty()) {
        throw out_of_range("Stack<>::pop(): empty stack");
    }
    elems.pop_back();
}
template<class T>
T Stack<T>::top() const {
    if (elems.empty()) {
        throw out_of_range("Stack<>::top(): empty stack");
    }
    return elems.back();
}
void testStack() {
    Stack<int> intStack;
    intStack.push(10);
    intStack.push(20);
    intStack.push(30);
    cout << intStack.top() << endl;
    intStack.pop();
    cout << intStack.top() << endl;
    intStack.pop();
    cout << intStack.top() << endl;
    intStack.pop();
}
int main() {
    testStack();
    try {
        Stack<string> strStack;
        strStack.push("Hello,world");
        strStack.push("Hello,C++");
        cout << strStack.top() << endl;
        strStack.pop();
        cout << strStack.top() << endl;
        strStack.pop();
        strStack.pop();
    }
    catch (exception const& ex) {
        cout << ex.what() << endl;
        return 1;
    }
    return 0;
}