Hi Joel,
I've been reading the docs. This is very clever! I wonder how it applies to expression templates with runtime code or Fusion with runtime components? A simple example would be a template plus function: template <typename A, typename B> auto plus(A const& a, B const& b) -> decltype(a+b) {return a+b;} The typical problem is an error if a+b is not allowed (e.g. a is an int but b is a std::vector). I don't see how your solution will help more than static_assert or better yet, Boost concepts. Regards,
Thank you for checking our solution. The goal of the "compile-time exceptions" is to be able to propagate error messages out from a chain of recursive template metafunction calls. What may be useful for template functions is the following: When you use a static assertion to verify the template arguments of your template function, you can write metafunctions as predicates that "throw" a "compile-time exception" when the condition fails (and return some value otherwise). You should be able to use them as predicates for static assertions: BOOST_MPL_ASSERT((is_exception< your predicate that may throw goes here... >)) This will break the compilation with some error message. If the "exception" that was "thrown" supports some pretty-printing solution (such as http://abel.web.elte.hu/mpllibs/metatest/index.html#_pretty_printing_custom_...) the developer can give the predicate which has issues to a pretty-printer in a separate compilation unit and get a human-readable and useful error message. Concept checking conditions may be pretty printed as well in a similar way. As I said earlier, this solution was originally developed for returning error messages from template metafunctions, they may be useful in template functions as well - I'll play with it and see if they can help there. Regards, Abel