JuniorTheoryCommon

What does the program print?

C++

#include <iostream>

int main() {
    int a = 1;
    int b = 2;
    int& r = a;
    int* p = &a;
    r = b;
    p = &b;
    *p = 3;
    std::cout << a << ' ' << b << '\n';
}

2 3

Expecting 1 3: r = b; does not re-bind r to b; it writes the value of b into a, which r still refers to.
Expecting 3 2: unlike a reference, a pointer can be pointed at another variable, so after p = &b; the write *p = 3; changes b.

Why can a pointer be left pointing at nothing, while a reference cannot?
When would you pass a pointer to a function rather than a reference?

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JuniorTheoryCommon

What does the program print?

C++

#include <iostream>

int main() {
    int a = 1;
    int b = 2;
    int& r = a;
    int* p = &a;
    r = b;
    p = &b;
    *p = 3;
    std::cout << a << ' ' << b << '\n';
}

2 3

Expecting 1 3: r = b; does not re-bind r to b; it writes the value of b into a, which r still refers to.
Expecting 3 2: unlike a reference, a pointer can be pointed at another variable, so after p = &b; the write *p = 3; changes b.

Why can a pointer be left pointing at nothing, while a reference cannot?
When would you pass a pointer to a function rather than a reference?

Back to questions Open topic in roadmap →Answer it yourself — Quiz