- range() : begin_(), end_() {}
- range(T begin, T end) : begin_(std::move(begin)), end_(std::move(end)) {}
- range(T value) : begin_(value), end_(value + 1) {}
+ Range() : begin_(), end_() {}
+ Range(T begin, T end) : begin_(std::move(begin)), end_(std::move(end)) {}
+ explicit Range(T value) : begin_(value), end_(value + 1) {}