Synopsis
Declared in header <boost/url/grammar/optional_rule.hpp>
template<class R_>
constexpr
optional_rule_t<R_>
optional_rule(R_ const& r);
Declared in header <boost/url/grammar/optional_rule.hpp>
template<class R_>
constexpr
optional_rule_t<R_>
optional_rule(R_ const& r);