[C++] 用Xcode来写C++程序[5] 函数的重载与模板

用Xcode来写C++程序[5] 函数的重载与模板

此节包括函数重载,隐式函数重载,函数模板,带参数函数模板

函数的重载

#include <iostream>
using namespace std;

int operate (int a, int b) {
    return (a * b);
}

double operate (double a, double b) {
    return (a / b);
}

int main ()
{
    int x    = 5;
    int y    = 2;
    double n = 5.0 ;
    double m = 2.0;

    cout << operate (x,y) << ‘\n‘;
    cout << operate (n,m) << ‘\n‘;

    return 0;
}

打印结果

10
2.5
Program ended with exit code: 0

函数模板

#include <iostream>
using namespace std;

// 模板
template <class T>
T sum (T a, T b) {
    T result;
    result = a + b;
    return result;
}

int main () {
    // 值初始化
    int i    = 5;
    int j    = 6;
    int k    = 0;
    double f = 2.0, g = 0.5, h;

    // 使用模板函数
    k = sum<int>(i, j);
    h = sum<double>(f, g);

    // 打印输出
    cout << k << ‘\n‘;
    cout << h << ‘\n‘;

    return 0;
}

打印结果

30
2.5
Program ended with exit code: 0

模板自动匹配

#include <iostream>
using namespace std;

template <class T, class U>
bool are_equal (T a, U b) {
    return (a == b);
}

int main () {

    // 自动模板识别
    if (are_equal(10,10.0))
        cout << "x and y are equal\n";
    else
        cout << "x and y are not equal\n";
    return 0;
}

打印结果

x and y are equal
Program ended with exit code: 0

带参数的模板

#include <iostream>
using namespace std;

template <class T, int N>
T fixed_multiply (T val) {
    return val * N;
}

int main() {
    std::cout << fixed_multiply<int, 2>(10) << ‘\n‘;
    std::cout << fixed_multiply<int, 3>(10) << ‘\n‘;
}

打印结果

20
30
Program ended with exit code: 0