JuniorTheoryCommon

Which line of this program does not compile?

C++

int main() {
    int count = 3;
    const int total = count + 1;
    constexpr int kLimit = 2 * 5;
    int copy = total;
    copy = kLimit;
    total = kLimit;
    return total + copy;
}

total = kLimit;: a const variable cannot get a new value

Expecting const to need a constant: that rule is constexpr's; a const takes any value once, count + 1 included, and forbids only later changes.
Expecting copy to inherit const: const belongs to a variable, not to its value, so a plain int copy of total can change.

Why can kLimit be declared constexpr, while total cannot?
When should a variable be const rather than constexpr?

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JuniorTheoryCommon

Which line of this program does not compile?

C++

int main() {
    int count = 3;
    const int total = count + 1;
    constexpr int kLimit = 2 * 5;
    int copy = total;
    copy = kLimit;
    total = kLimit;
    return total + copy;
}

total = kLimit;: a const variable cannot get a new value

Expecting const to need a constant: that rule is constexpr's; a const takes any value once, count + 1 included, and forbids only later changes.
Expecting copy to inherit const: const belongs to a variable, not to its value, so a plain int copy of total can change.

Why can kLimit be declared constexpr, while total cannot?
When should a variable be const rather than constexpr?

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