constexpr bool operator==(const address_v6& a, const address_v6& b) noexcept;
Returns: a.to_bytes() == b.to_bytes() && a.scope_id() == b.scope_id().
constexpr bool operator!=(const address_v6& a, const address_v6& b) noexcept;
Returns: !(a == b).
constexpr bool operator< (const address_v6& a, const address_v6& b) noexcept;
Returns: tie(a.to_bytes(), a.scope_id()) < tie(b.to_bytes(), b.scope_id()).
constexpr bool operator> (const address_v6& a, const address_v6& b) noexcept;
Returns: b < a.
constexpr bool operator<=(const address_v6& a, const address_v6& b) noexcept;
Returns: !(b < a).
constexpr bool operator>=(const address_v6& a, const address_v6& b) noexcept;
Returns: !(a < b).