David Abrahams wrote:
Hi,
I have this code that isn't compiling because of the "forwarding problem" limitation of boost::bind:
std::for_each( make_difference_iterator(p->second.begin()) , make_difference_iterator(p->second.end()) , boost::bind(&fu::writeVInt, &prox, _1));
Nice namespace name.
The problem is that an implicit conversion is required between the reference type of the difference_iterator and the argument type of writeVInt.
It seems to me that, since I know that binding to an rvalue is required, we ought to have a way to say "force this to be a const ref". I thought of something like
std::for_each( make_difference_iterator(p->second.begin()) , make_difference_iterator(p->second.end()) , boost::bind(&fu::writeVInt, &prox, boost::cref(_1))); ^^^^^^^^^^^^ ^
I know it's not pretty, but it sorta does what we want. Thoughts?
Have you tried to implement it? ;-) The current bind way to work around the above problem is to use an adaptor that fixes its signature to, for example, void(fu const &). Choices are function<void(fu const &)> and make_adaptable<void, fu const &> (in boost/bind/make_adaptable.hpp). Lambda also provides its own mechanisms.