[Boost-bugs] [Boost C++ Libraries] #10393: Add begin/end specialization for optional<T> type

Subject: [Boost-bugs] [Boost C++ Libraries] #10393: Add begin/end specialization for optional<T> type
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2014-08-22 12:26:04

#10393: Add begin/end specialization for optional<T> type
---------------------------------------+-----------------------
 Reporter:  khimru@…                   |      Owner:  fcacciola
     Type:  Feature Requests           |     Status:  new
Milestone:  Boost 1.57.0               |  Component:  optional
  Version:  Boost 1.56.0               |   Severity:  Cosmetic
 Keywords:  optional, for, begin, end  |
---------------------------------------+-----------------------
 optional<T> could be used in many places as if it was just T, but, since
 C++ does not apply two levels of constructions one could not use this
 natural looking construct for optional containers:

 if (opt_container) {
   for (auto& element : opt_container) {
      ...
   }
 }

 Simple specialization of begin()/end() functions could solve this problem:

 namespace std {

 template<class T>
 inline auto
 begin(const boost::optional<T>& opt) -> decltype(opt.get().begin()) {
  return opt.get().begin();
 }

 template<class T>
 inline auto
 begin(boost::optional<T>& opt) -> decltype(opt.get().begin()) {
   return opt.get().begin();
 }

 template<class T>
 inline auto
 end(const boost::optional<T>& opt) -> decltype(opt.get().end()) {
   return opt.get().end();
 }

 template<class T>
 inline auto
 end(boost::optional<T>& opt) -> decltype(opt.get().end()) {
   return opt.get().end();
 }

 }

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/10393>
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