I mean IDL-like, as in valid c++ that is almost as easy to read as an IDL (to me at least) but without losing the ability to dive in to the binding if necessary

I mean IDL-like, as in valid c++ that is almost as easy to read as an IDL (to me at least) but without losing the ability to dive in to the binding if necessary. If you're trying to produce a binding that feels idiomatic in the target language, I'd say this is important, and this is where Swig-like approaches show their weakness. I think the author of Swig shares this sentiment: (http://code.activestate.com/lists/python-dev/109281/ http://code.activestate.com/lists/python-dev/109281/).