On Nov 8, 2006, at 1:42 AM, Sebastian Weber wrote:
Hi Stuart!
Try this -
boost::function< double (std::size_t) > wf = (sIndex < m_maxIndex +1) ? boost::function< double (std::size_t) >( boost::lambda::bind(boost::ref(m_cf), sDeg, boost::lambda::_1) ) ) : ( boost::ref(*m_wf) );
i.e. make sure the first expression is explicitly a boost::function< double (std::size_t) >, as the second is convertible to that.
Cool, this works! But why is this explicit cast necessary in this case?
It follows from the language rules of the ? : operator. Roughly, the branches have to have same types, or one convertible to another. The types of the expressions in the branches in your example look something like this: lambda_functor< some long template mess here > lambda_functor< some long template mess here, but different than the one in the other branch> These types are not convertible. Best, Jaakko Järvi