[Boost-bugs] [Boost C++ Libraries] #1422: const_iterator does not equate to value_type (or const value_type)

Subject: [Boost-bugs] [Boost C++ Libraries] #1422: const_iterator does not equate to value_type (or const value_type)
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2007-11-08 18:18:52

#1422: const_iterator does not equate to value_type (or const value_type)
----------------------------------------------------+-----------------------
 Reporter:  Bill Buklis <boostuser_at_[hidden]>     |       Owner:  nesotto      
     Type:  Bugs                                    |      Status:  new          
Milestone:  To Be Determined                        |   Component:  ptr_container
  Version:  Boost 1.34.1                            |    Severity:  Problem      
 Keywords:  ptr_map, ptr_container, const_iterator  |  
----------------------------------------------------+-----------------------
 In ptr_map, const_iterator does not represent value_type. Given this map:

 typedef boost::ptr_map<DWORD, int> BOOSTMAP;

 BOOSTMAP::value_type equates to:

 boost::ptr_container_detail::ref_pair<DWORD, int* const>

 BOOSTMAP::iterator does return this, but const_iterator returns:

 boost::ptr_container_detail::ref_pair<DWORD, const int* const> which is
 unlike std::map which represents const value_type for const_iterator.
 Since this is a different structure, it's incompatible with
 BOOSTMAP::value_type.

 The following code works using std::map:


 {{{
 typedef std::map<DWORD, int*> STDMAP;
 int                     sample = 5;
 STDMAP          sm;

 sm.insert( STDMAP::value_type(10,&sample) );

 STDMAP::iterator                sfirst = sm.begin();
 STDMAP::const_iterator          scfirst = sm.begin();
 STDMAP::value_type&             svt = *sfirst;
 const STDMAP::value_type&       scvt = *scfirst;
 }}}

 But, the same fails on the last line with boost::ptr_map

 {{{
 typedef boost::ptr_map<DWORD, int> BOOSTMAP;
 BOOSTMAP        bm;
 DWORD           key = 10;

 bm.insert( key, new int(5) );

 BOOSTMAP::iterator              bfirst = bm.begin();
 BOOSTMAP::const_iterator        bcfirst = bm.begin();
 BOOSTMAP::value_type&           bvt = *bfirst;
 const BOOSTMAP::value_type&     bcvt = *bcfirst;
 }}}

-- 
Ticket URL: <http://svn.boost.org/trac/boost/ticket/1422>
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