AMDG Douglas Gregor <dgregor <at> osl.iu.edu> writes:
There are several libraries that have this kind of problem. typeof needs registrations, serialization needs serialize() functions, MPI needs datatype traits, etc. I wonder if we can solve this problem for all of Boost with some kind of automatic scheme that says: if you include header A from one library and header B from another library, you automatically get whatever glue makes A and B work well together.
It's relatively simple to implement this for two headers. In header A you have:
#ifdef HEADER_B_INCLUDED # include <glue_a_and_b.hpp> #endif
In header B you have:
#ifdef HEADER_A_INCLUDED # include <glue_a_and_b.hpp> #endif
For the general case, we would probably want a "glue" subdirectory whose directory mimics the Boost directory structure (like a generalized version of your typeof_registrations suggestion). Each header in "glue" would have a bunch of #ifdef's checking all of the various other library/header names and including the appropriate glue code.
Overall, it's O(N^2) work in the number of data structures/headers/libraries (depending on how we chop it up), but users would get all of the important glue "for free".
- Doug
The work needs to be done anyway! This is just a convenient way to package it. There should probably be some way to automate the process. For example every library that need this feature could have a directory nested directory called auto_include. Then the header boost/typeof/detail/auto_include/ref.hpp e.g. should contain a comment looking like: // boostauto_include: boost/typeof/typeof.hpp boost/ref.hpp This will cause two things to happen: a) The file boost/auto_include/boost/typeof/typeof.hpp will be generated and will look like #ifndef BOOST_AUTO_INCLUDE_BOOST_TYPEOF_TYPEOF_HPP_INCLUDED #define BOOST_AUTO_INCLUDE_BOOST_TYPEOF_TYPEOF_HPP_INCLUDED #endif #ifdef BOOST_AUTO_INCLUDE_BOOST_REF_HPP_INCLUDED #include <boost/typeof/detail/auto_include/ref.hpp> #endif // more stuff involving typeof Similarly, boost/auto_include/boost/ref.hpp will be updated. b) The headers boost/ref.hpp and boost/typeof/typeof.hpp will be checked to verify that they contain #include <boost/auto_include/boost/ref.hpp> and #include <boost/auto_include/boost/typeof/typeof.hpp> respectively. It's probably not a good idea to automatically update these files. I'm willing to write the necessary script if this seems like a good way to go. In Christ, Steven Watanabe