Re: [Boost-bugs] [Boost C++ Libraries] #5991: find_ptr (find wrapper)

Subject: Re: [Boost-bugs] [Boost C++ Libraries] #5991: find_ptr (find wrapper)
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2011-11-04 07:37:07

#5991: find_ptr (find wrapper)
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  Reporter:  Olaf van der Spek <olafvdspek@…>          |       Owner:  joaquin    
      Type:  Feature Requests                          |      Status:  closed     
 Milestone:  To Be Determined                          |   Component:  multi_index
   Version:  Boost 1.47.0                              |    Severity:  Problem    
Resolution:  wontfix                                   |    Keywords:             
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Comment (by joaquin):

 Replying to [comment:7 Olaf van der Spek <olafvdspek@…>]:
 > Replying to [comment:6 joaquin]:
 > > Why a pointer to second?
 >
 > Because the key is known already.
 >
 > > This is not consistent with the semantics of std::map, which returns
 an iterator to the whole element (the key-value pair), not the value
 alone.
 >
 > std::map doesn't have find_ptr().

 Of course, but it has find(), which I understand you're copying semantics
 from, except that you return a pointer (null if no element was found)
 rather than an iterator (pointing to end if no element was found.)

 >
 > > > IMO the wrapper is useful every time you use a map like container.
 > >
 > > In either case, find_ptr can be provided as an (overloaded) function,
 no need to have as a built-in member function. Thus my reluctance to
 address your request.
 >
 > Can it? I can't (easily) select another overload for containers (like
 multi_index) that don't have a pair value_type.

 multi_index_containers don't sport a notion of second_type. But you can
 use the same wrapper as you're currently doing with std::set. Remember
 this conversarion began with your request for a member function returning
 a value_type* (not a pointer to the second part of the value.)

 What problems are you having with defining an overload for
 multi_index_containers?

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/5991#comment:9>
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