[Boost-bugs] [Boost C++ Libraries] #6357: Resolve ambiguity for unqualified call to begin/end

Subject: [Boost-bugs] [Boost C++ Libraries] #6357: Resolve ambiguity for unqualified call to begin/end
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2012-01-04 14:58:38

#6357: Resolve ambiguity for unqualified call to begin/end
------------------------------+---------------------------------------------
 Reporter:  theller           |       Owner:  theller
     Type:  Bugs              |      Status:  new    
Milestone:  To Be Determined  |   Component:  phoenix
  Version:  Boost 1.48.0      |    Severity:  Problem
 Keywords:                    |  
------------------------------+---------------------------------------------
 On 12/16/2011 10:44 AM, Nathan Ridge wrote:
 >
 > Hello,
 >
 > I am running into a problem where an unqualified call to begin()
 > on a range type whose template parameters include a Boost.Phoenix
 > type (for examle filtered_range<Pred, R>  where Pred is a phoenix
 > function) is ambiguous because, in addition to the intended
 > std::begin, phoenix::begin is being found by ADL.
 >
 > What can be done about this? There exists precedent for placing
 > boost::xxx::begin/end functions in ADL barrier namespaces because
 > C++11 encourages unqualified calls to begin/end (specifically,
 > this was done for boost::range::begin/end). Should the same thing
 > be done for Phoenix?
 >
 > Here is a minimal example that reproduces the problem:

 {{{
 #include<iterator>

 #include<boost/range/adaptor/filtered.hpp>
 #include<boost/phoenix/phoenix.hpp>

 using std::begin;

 {{{
 int main()
 {
      using boost::phoenix::arg_names::arg1;
      using boost::adaptors::filtered;

      int v[5];
      const auto&  f = v | filtered(arg1<  0);
      begin(f);
 }
 }}}

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/6357>
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