Example of c++17ish Iterator pattern.

iterator_example.cpp

#include <cstdio>

using Bar = int;

class Foo {
public:
    struct Iter {
        Iter& operator++() { ++ptr; return *this; }
        bool operator!=(Iter const& other) const { return ptr != other.ptr; }
        Bar& operator*() { return *ptr; }
        Bar* ptr;
    };
    Iter begin() { return Iter{&array_[0]}; }
    Iter end() { return Iter{&array_[N]}; }

private:
    static constexpr unsigned N = 5;
    Bar array_[N] = {1, 2, 3, 4, 5};
};

int main() {
    for (Bar value : Foo()) {
        printf("%d ", value);
    }
    puts("");
}