Ptr and ref C++

refptr.cpp

#include <iostream>
using namespace std;

int ma8in() {
    int a = 3, b = 7, c, nums[100] = { 11, 22, 33 };
    int *p1 = &a, *p2 = &b, *p3 = &c, *pn = nums;
    void *p = p1; p3 = (int*)p;
    c = a + b;
    cout << "a="  << a  << ", b="  << b <<  ", c=" << c
       << ", *p1=" << *p1 << ", *p2=" << *p2 << ", *p3=" << *p3 << endl;
    a = 12;
    p1 = p2;
    *p1 = *p3;
    p1 = 0; p2 = NULL; p3 = nullptr;
    if (p1)
        cout << "*p1 points to " << *p1 << endl;
    else
        cout << "p1 is null pointer" << endl;
    cout << "a="  << a  << ", b="  << b <<  ", c=" << c
       << ", *p1=" << *p1 << ", *p2=" << *p2 << ", *p3=" << *p3 << endl;
    for (int i = 0; i < sizeof(nums)/sizeof(nums[0]); i++)
        cout << " " << pn[i];
    cout << endl;
    return 0;
}























/// Задание 1: сделать калькулятор (ввод двух значений и операции) с вычислением
/// в отдельных функциях через ссылки. Операции: +, -, *, /, логарифм, модуль
/// Задание 2: перейти от ссылок к указателям (N.B.: операции &foo и *pfoo)
int add(const int &x, const int &y) { return x + y; }
void transpose(int &x, int &y) { int t = x; x = y; y = t; }
int main() {
    int a = 3, b = 7, c, nums[100] = { 11, 22, 33 };
    int *p1, *p2, *p3, *p = nums;  void *x = p;
    int &ref1 = a, &ref2 = b, &ref3 = c;

    ref3 = add(a, b);
    transpose(a, b);
    cout << "a=" << a << ", b=" << b << ", c=" << c << endl;
    if (p1)
        cout << "p1 points to " << *p1 << endl;
    else
        cout << "p1 is null pointer" << endl;
    *p1 = 123;
    for (int i = 0; i < sizeof(nums)/sizeof(nums[0]); i++)
        cout << " " << p[i];
    cout << endl;
    return 0;
}