函数指针的应用

#include <iostream>

#define __in
#define __out

using namespace std;

int Add( __in int a, __in int b )
{
    cout << ">>>Add function running..." << endl;
    return a + b;
}

int Substract( __in int a, __in int b )
{
    cout << ">>>Substract function running..." << endl;
    return a - b;
}

int Error( int a, int b )
{
    cout << ">>>Input error!" << endl;
    return 0;
}

int main()
{
    typedef int( * ADD_FUNC )( int, int );
    ADD_FUNC lpfun = NULL;
    for ( int i = 0; i < 5; i++ )
    {
        cout << "\n-------------" << endl;
        cout << "1. Add" << endl;
        cout << "2. Substract" << endl;
        cout << "which action do you want? ";
        int choice = 0;
        cin >> choice;
        switch ( choice )
        {
            case 1: lpfun = Add; break;
            case 2: lpfun = Substract; break;
            default: lpfun = Error;
        }
        lpfun( 3, 5 );
    }

    return 0;
}