《C++ Primer》学习 之 函数指针相关用法

/*
　　函数指针相关用法
*/

#define _CRT_SECURE_NO_WARNINGS
#define HOME
//#define NDEBUG
#include <iostream>
#include <stdexcept>
#include <cassert>
#include <ctype.h>
#include <locale>
#include <iterator>
#include <cmath>
#include <string>
#include <vector>
#include <initializer_list>
#include <ctime>
using namespace std;
using ptrFun = int(*)(int, int);

int myAdd(int x, int y)
{
    return (x + y);
}
int mySub(int x, int y)
{
    return (x - y);
}

int myMul(int x, int y)
{
    return (x * y);
}

int myDiv(int x, int y)
{
    if (0 == y)
    {
        std::cerr << "error : 除以0" << endl;
        return -1;
    }
    else
    {
        return (x / y);
    }
}

void Compute(int x, int y, int (*p)(int, int))
{
    cout << p(x, y) << endl;
}


int main(int argc, char **argv)
{
#ifdef HOME
    //freopen("in", "r", stdin);
    //freopen("out", "w", stdout);
#endif

    cout << "方法一：" << endl;
    // 以下两种声明方式也是可以的
    //vector<int(*)(int, int)> vecFunc;
    //vector<ptrFun> vecFunc;
    vector<decltype(myAdd)*> vecFunc;
    vecFunc.push_back(myAdd);
    vecFunc.push_back(mySub);
    vecFunc.push_back(myMul);
    vecFunc.push_back(myDiv);
    for (int i = 0; i < vecFunc.size(); ++i)
    {
        cout << vecFunc[i](6, 3) << endl;
        cout << (*vecFunc[i])(6, 3) << endl;
        Compute(6, 3, vecFunc[i]);
    }

    cout << endl << "方法二：" << endl;
    decltype(myAdd) *p1 = myAdd, *p2 = mySub, *p3 = myMul, *p4 = myDiv;
    vector<decltype(myAdd)*> vec1Func = { p1, p2, p3, p4 };
    for (int i = 0; i < vec1Func.size(); ++i)
    {
        cout << vec1Func[i](6, 3) << endl;
        cout << (*vec1Func[i])(6, 3) << endl;
        Compute(6, 3, vec1Func[i]);
    }

#ifdef HOME
    std::cerr << "Time elapsed: " << clock() / CLOCKS_PER_SEC << " ms" << endl
        << "message: " << __FILE__ << endl
        << "        : in function " << __func__
        << " at line " << __LINE__ << endl
        << "          Compiled on " << __DATE__
        << " at " << __TIME__ << endl;
#endif
    return 0;
}