Re: [Boost-users] boost::variant and SGI's compose1 cause constness error

From: Erwin (junkmail.hoefling_at_[hidden])
Date: 2005-07-07 03:25:10

Thanks Peter Dimov!

When I posted the message, the scales fell from my eyes and I realized a  
even simpler workaround: Simply perform the loop myself and use the  
explicit version of apply_visitor:

Replace the for_each construction

     for_each( v.begin(), v.end(),
               compose1(apply_visitor(_dummy), select1st<TPair>() ) );  //  
yields a const error

by the explicit loop

     for( vector<TPair>::iterator it=v.begin(); it!=v.end(); ++it )
         apply_visitor(dummy(), it->first);

This is a little bit less general since we have to know the type of v in  
advance, however, for me it works.

Anyway, I would consider the problem as a bug in boost::visitor. The  
remark in apply_visitor_delayed.hpp about the dead reference doesn't make  
sense to me. As long as apply_visitor is in action, a temporary visitor  
object is alive, isn't it?