Step 1 of 5

Making a class iterable

You've used range-for on vectors, strings, maps and arrays. Your own classes can join in, and it's easier than it looks, because range-for is just shorthand. The compiler rewrites it into iterator calls:

for (auto& x : c) { ... }
// becomes roughly:
for (auto it = c.begin(), end = c.end(); it != end; ++it) { auto& x = *it; ... }

So any type with begin() and end() members works with range-for, and with every standard algorithm. If your class stores its data in a plain array, pointers are perfectly good iterators: they already support *, ++ and !=.

#include <algorithm>
#include <iostream>

class Week {
public:
    void set(int day, double hours) { hours_[day] = hours; }
    double* begin() { return hours_; }
    double* end() { return hours_ + 7; }               // one past the last day
    const double* begin() const { return hours_; }
    const double* end() const { return hours_ + 7; }

private:
    double hours_[7] = {};
};

double total(const Week& w) {
    double t = 0;
    for (double h : w) t += h;                          // uses the const versions
    return t;
}

int main() {
    Week w;
    w.set(0, 8);
    w.set(2, 6.5);
    for (double& h : w) h += 0.5;                       // non-const: modify in place
    std::cout << total(w) << "\n";
    std::cout << *std::max_element(w.begin(), w.end()) << "\n";
}

18
8.5

Why two versions?

• total receives a const Week&. On a const object, only const member functions can be called, so it needs begin() const and end() const. Those return const double*, so the loop can read but not change.
• The loop in main modifies the hours through double&, which needs the non-const versions returning double*.

Providing both is the standard pattern for every container.

Your task: only the filled part

Scoreboard has room for 8 scores but only count_ are real. So end() is scores_ + count_, not scores_ + 8. Then range-for and algorithms automatically see only the scores that were added.

Your turn: give Scoreboard begin() and end() (both a non-const and a const version) that return pointers into its fixed array, covering only the count_ scores that were added.

Next: Writing an iterator class