C++ : 模版

模板类

用模板类定义int string类型的类
用类来实现栈

#include <iostream>
#include <vector>
#include <stdexcept> //throw
//#include <cstdlib> <==> #include <stdlib.h>
using namespace std;
template <class T>
class Stack
{ 
  private: 
    vector<T> elems;      // 元素
  public: 
    void push(T const&);  // 入栈
    void pop();           // 出栈
    T top() const;        // 返回栈顶元素
    bool empty() const    // 如果为空则返回真
    { return elems.empty(); } 
}; 

template <class T>
void Stack<T>::push (T const& elem){
    elems.push_back(elem); // 追加传入元素的副本
} 

template <class T>
void Stack<T>::pop (){
    if (elems.empty()) 
    { throw out_of_range("Stack<>::pop(): empty stack"); }
    elems.pop_back();  // 删除最后一个元素       
} 

template <class T>
T Stack<T>::top () const 
{ 
    if (elems.empty()) 
    { throw out_of_range("Stack<>::top(): empty stack"); }
    return elems.back(); //返回最后一个元素的副本
}
int main() 
{
    try{
        Stack<int> intStack;              // int 类型的栈 
        Stack<string> stringStack;    // string 类型的栈 

        //操作int类型的栈 
        intStack.push(7); 
        cout << intStack.top() <<endl; 
        //操作string类型的栈 
        stringStack.push("hello"); 
        cout << stringStack.top() << std::endl; 
        stringStack.pop(); 
        stringStack.pop(); 
    } 
    catch (exception const& ex){ //catch 异常 of the throw
        cerr << "Exception: " << ex.what() <<endl; 
        return -1;
    } 
}
/* result: 7 hello Exception: Stack<>::pop(): empty stack */

模板函数

用来实现不同类型值的比较

#include <iostream>
#include <string>
using namespace std;
 
template <typename T>
inline T const& Max (T const& a, T const& b){
    return a < b ? b:a; 
} 
int main ()
{
    int i = 39;
    int j = 20;
    cout << "Max(i, j): " << Max(i, j) << endl; 
 
    double f1 = 13.5; 
    double f2 = 20.7; 
    cout << "Max(f1, f2): " << Max(f1, f2) << endl; 
 
    string s1 = "Hello"; 
    string s2 = "World"; 
    cout << "Max(s1, s2): " << Max(s1, s2) << endl; 
 
   return 0;
}

模板类的继承

#include <iostream>
#include <string>
using namespace std;
enum eColor { none = 0, red, white};

class Color{
public:
    Color(eColor color);
    string getStrColor();
protected:
    eColor mColor;
};
Color::Color(eColor _color){
    mColor = _color;
}
string Color::getStrColor(){
    switch (mColor){
        case red:return "red";
        case white:return "white";
    }
}

template <typename T>
class Circle : public Color{
public:
    Circle(T radius, eColor color);
    T area();
protected:
    T radius;//半径r
};
template <typename T>
Circle<T>::Circle(T _radius, eColor _color) : Color(_color){
    radius = _radius;
}
template <typename T>
T Circle<T>::area(){
    return 3.14 * radius * radius;
}

template <typename T>
class Sphere : public Circle<T>{
public:
    Sphere(T radius, eColor color);
    T volume();
};
template <typename T>
Sphere<T>::Sphere(T _radius, eColor _color) : Circle<T>::Circle(_radius, _color){}
template <typename T>
T Sphere<T>::volume(){
    return 4 * 3.14 * this->radius * this->radius * this->radius / 3;
}

int main(int argc, char* argv[]){
    Sphere<double> sphereA(10.0, red);
    cout << "Volume: " << sphereA.volume() << endl;
    cout << "Area: " << sphereA.area() << endl;
    cout << "Color: " << sphereA.getStrColor() << endl;
}