Synopsis

Declared in header </boost/url/grammar/parse.hpp#L113[boost/url/grammar/parse.hpp,window=blank_]>

template<class Rule>
constexpr
enable_if<is_rule<Rule>::value && !std::is_same<Rule, detail::rule_ref<Rule>>::value, rule_ref<Rule>>::type
ref(const Rule& r) noexcept;