1 函式模板

#include <iostream>
using namespace std;

template <typename T>
T square(T a)
{
    return a * a;
}

int main(void)
{
    cout << square<int>(3) << endl;     // 可以顯式告訴編譯器是什麼型別，也可以讓編譯器推斷
    cout << square(3) << endl;
    cout << square<char>(9.3
 
) << endl;    //  結果是Q ，81的ASCII碼
    cout << square<int>(9.3) << endl;     // 結果81
    cout << square(5.5) << endl;         // 30.25 編譯器自己推斷為double
}

2 類模板

#include <iostream>
using namespace std;

template <typename T>
T square(T a)
{
    return a * a;
}

template 
 
<typename T>
class win
{
private:
    T arr[10];
    int size;
public:
    win():size(0) {cout << "creater" << endl; }
    ~win(){};
    int  getSize()const{ return size; }
    T get(int i)const{ return arr[i];}
    void push(T x) { arr[size] = x; size++;}
    void print()const;

};

template 
 
<typename T>
void win<T>::print()const{ 
    for (int i = 0; i < size; i++) {
        cout << arr[i] << endl;
    }
}


template <typename T>
win<T> operator*(const win<T> &left, const win<T> &right)
{
    win<T> ret;
    for( int i = 0 ; i < right.getSize(); i++) {
        ret.push(left.get(i) * right.get(i));
    }
    return ret;
}

int main(void)
{
    win<int> a;
    a.push(1);
    a.push(2);
    a.push(3);
    a.push(4);
    a.push(5);
    a.push(6);
    a.print();
    a = square(a);
    a.print();
}

a = square(a);這處會先呼叫函式模板然後由於定義了類win的乘法，呼叫operator *