path proximate(const path& p, error_code& ec);
path proximate(const path& p, const path& base = current_path()); path proximate(const path& p, const path& base, error_code& ec);
weakly_canonical(p).lexically_proximate(weakly_canonical(base));
weakly_canonical(p, ec).lexically_proximate(weakly_canonical(base, ec));