On Fri, Mar 19, 2010 at 11:24 AM, Nat Goodspeed
Kim Kuen Tang wrote:
Nat Goodspeed schrieb:
I'm a bit surprised not to find existing support for std::vector; presumably that's been done a few times by individuals.
The size of std:::vector is not an mpl integral constant ( not known in compile time). So std::vector is not a sequence in the sense of fusion. See
http://boost-spirit.com/dl_more/fusion_v2/libs/fusion/doc/html/fusion/sequen...
Then maybe boost::fusion::invoke() isn't what I'm looking for.
Nonetheless it comes frustratingly close: the preprocessor iteration to handle various arities is already done.
(In fact handling some number of C++ arities is (re)implemented in a surprising number of different Boost libraries.)
Presumably Boost.Python has internal machinery very like what I want, receiving an arbitrary sequence of Python variant objects and using them to populate the parameter list of some C++ callable. Of course I don't want to start basing production code on an undocumented implementation detail, though.
Still looking for a Boost feature to apply (e.g.) a std::vector of parameter values to a C++ callable... thanks for additional suggestions.
Actually I have done that same kind of thing as what you are wanting with my RPC library using Boost::Fusion. Statically you build up a recursive functor that creates the fusion sequence that matches the function, and dynamically you populate it with the vector elements and invoke it (or throw an exception if you have too many or too few vector elements?). It is actually quite easy and Boost has an example of that in the boost::function_types examples.