:relfileprefix: ../../../../
[#0300D2493EAB6030FCAB34A716B6CA44CF5533A5]

= Friend optional_rule



== Synopsis

Declared in header `</boost/url/grammar/optional_rule.hpp#L76[boost/url/grammar/optional_rule.hpp,window=blank_]>`

[source,cpp,subs="verbatim,macros,-callouts"]
----
template<class R_>
friend
constexpr
xref:boost/urls/grammar/optional_rule_t.adoc[optional_rule_t]<R_>
optional_rule(const R_& r);
----