Hi Joel, On Wed, Dec 10, 2008 at 12:19 PM, Joel de Guzman <joel@boost-consulting.com> wrote:
Dean Michael Berris wrote:
On Wed, Dec 10, 2008 at 1:37 AM, David Abrahams <dave@boostpro.com> wrote:
Here:
http://svn.boost.org/svn/boost/branches/zip_iterator_fusion/boost/boost/iter...
Thanks Dave, I'll give this a try.
It needs a little work for fusion still. While fusion is TR1 savvy, it thinks (through Boost TR1 [http://tinyurl.com/5awnzn]) that it *is* TR1. Not any other rendition of it. So, fusion needs to somehow detect which TR1 version you are using (Boost or gcc). In the case of Boost, nothing needs to be done. In the case of GCC's, fusion needs an adapter similar to that of fusion/boost_tuple adapter.
I just took a look at Dave's code, and it does need a few things to get going with the current state of fusion in trunk. I'm trying to hack on it to make it work with the latest fusion and I see that it uses a function 'fusion::generate(...)'. I'm guessing that 'generate' is supposed to turn a view into a 'real' container, but somehow I'm not sure exactly what kind of container is required. I'm guessing it should be converted to make_tuple or make_vector, but I need to dig deeper to figure it out.
Any suggestion on a better way to do the mapping/adapting appreciated. Adapting fusion to any other tuple-like entity is easy (Dean, you might want to give it a try, patch welcome). The tricky part is how to disable the one over the other on availability.
Any thoughts?
About an adapter, it doesn't look like rocket science so I can try it out locally first to see if I can try adapting GCC's TR1 tuple to support tag dispatching on which fusion seems to depend on to "get things right". If only we can overload the assignment operator as a non-member function then this would all be a matter of defining (invalid at the moment): namespace { template <class T0, ... class TN> std::tr1::tuple<T0, ...TN> & operator=( std::tr1::tuple<T0, ... TN> & lhs, boost::fusion::tuple<T0, ... TN> && rhs ) { // assign the values from rhs to lhs // maybe using fusion::for_each return lhs; } template <class T0, ... class TN> std::tr1::tuple<T0, ...TN> & operator=( std::tr1::tuple<T0, ... TN> & lhs, boost::fusion::tuple<T0, ... TN> const & rhs ) { // assign the values from rhs to lhs // maybe using fusion::for_each return lhs; } } Wishful thinking I might think, but would definitely be a welcome addition to C++. Thanks again, and I hope to be able to make progress soon. (In the meantime I just moved away from GCC's TR1 tuple and stuck with Boost.Tuple ;) ). -- Dean Michael C. Berris Software Engineer, Friendster, Inc.