[Boost-bugs] [Boost C++ Libraries] #3881: Make BOOST_FOREACH auto (using BOOST_AUTO) aware

Subject: [Boost-bugs] [Boost C++ Libraries] #3881: Make BOOST_FOREACH auto (using BOOST_AUTO) aware
From: Boost C++ Libraries (noreply_at_[hidden])
Date: 2010-01-29 23:37:17

#3881: Make BOOST_FOREACH auto (using BOOST_AUTO) aware
--------------------------+-------------------------------------------------
 Reporter:  Mark          |       Owner:  eric_niebler  
     Type:  Patches       |      Status:  new           
Milestone:  Boost 1.42.0  |   Component:  foreach       
  Version:  Boost 1.41.0  |    Severity:  Not Applicable
 Keywords:                |  
--------------------------+-------------------------------------------------
 Hi,

 I was playing with BOOST_FOREACH and disliked the need for a typedef to be
 able to use value_type so i tried to find a solution that didn't require a
 typedef or a seperate std::pair<something, something> iterator; The first
 solution was using BOOST_TYPEOF(something)::value_type but i wasn't happy
 with that way. Then the people in the #boost channel made me aware of the
 "auto" keyword for the new C++0x revision (and i had no clue what auto
 would mean). Following that someone tole me that i probably needed a
 BOOST_FOREACH function that is auto (BOOST_AUTO) aware but it wasn't made
 and i never made or edited a macro before.

 By now you probably guess it. I made a BOOST_FOREACH that is auto aware!
 And i hereby share that code with you. At the moment it's a little hard
 for me to make a diff file so please forgive me for "just" adding it in
 here. The following 2 macros need to be added to the "foreach.hpp" file at
 the very end of it:

 {{{
 #define BOOST_FOREACH_AUTO(VAR, COL)
 \
     BOOST_FOREACH_PREAMBLE()
 \
     if (boost::foreach_detail_::auto_any_t BOOST_FOREACH_ID(_foreach_col)
 = BOOST_FOREACH_CONTAIN(COL)) {} else   \
     if (boost::foreach_detail_::auto_any_t BOOST_FOREACH_ID(_foreach_cur)
 = BOOST_FOREACH_BEGIN(COL)) {} else     \
     if (boost::foreach_detail_::auto_any_t BOOST_FOREACH_ID(_foreach_end)
 = BOOST_FOREACH_END(COL)) {} else       \
     for (bool BOOST_FOREACH_ID(_foreach_continue) = true;
 \
               BOOST_FOREACH_ID(_foreach_continue) &&
 !BOOST_FOREACH_DONE(COL);                                    \
               BOOST_FOREACH_ID(_foreach_continue) ?
 BOOST_FOREACH_NEXT(COL) : (void)0)                            \
         if
 (boost::foreach_detail_::set_false(BOOST_FOREACH_ID(_foreach_continue)))
 {} else                      \
         for (BOOST_AUTO(VAR, BOOST_FOREACH_DEREF(COL));
 !BOOST_FOREACH_ID(_foreach_continue); BOOST_FOREACH_ID(_foreach_continue)
 = true)

 #define BOOST_REVERSE_FOREACH_AUTO(VAR, COL)
 \
     BOOST_FOREACH_PREAMBLE()
 \
     if (boost::foreach_detail_::auto_any_t BOOST_FOREACH_ID(_foreach_col)
 = BOOST_FOREACH_CONTAIN(COL)) {} else   \
     if (boost::foreach_detail_::auto_any_t BOOST_FOREACH_ID(_foreach_cur)
 = BOOST_FOREACH_RBEGIN(COL)) {} else    \
     if (boost::foreach_detail_::auto_any_t BOOST_FOREACH_ID(_foreach_end)
 = BOOST_FOREACH_REND(COL)) {} else      \
     for (bool BOOST_FOREACH_ID(_foreach_continue) = true;
 \
               BOOST_FOREACH_ID(_foreach_continue) &&
 !BOOST_FOREACH_RDONE(COL);                                   \
               BOOST_FOREACH_ID(_foreach_continue) ?
 BOOST_FOREACH_RNEXT(COL) : (void)0)                           \
         if
 (boost::foreach_detail_::set_false(BOOST_FOREACH_ID(_foreach_continue)))
 {} else                      \
         for (BOOST_AUTO(VAR, BOOST_FOREACH_DEREF(COL));
 !BOOST_FOREACH_ID(_foreach_continue); BOOST_FOREACH_ID(_foreach_continue)
 = true)
 }}}

 Mention me in the release notes (as markg85) for the next version if this
 gets added ^_^

 Bye,
 Mark

-- 
Ticket URL: <https://svn.boost.org/trac/boost/ticket/3881>
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