AMDG Alexander Nasonov <alnsn <at> yandex.ru> writes:
Wow! I like it. I haven't implemented it yet but the sketch looks absolutely correct.
There's a little problem. How to get the arguments from the opening macro to the closing one without interfering with another local function. I think I've found a solution for that, too. The key is that we need to declare a variable if it has not yet been declared. We can test whether it has been declared by creating a global with the same name and using a sizeof expression. So, now we need some syntax that will be either a declaration or something else depending on a boolean condition. To do this we can take advantage of the ambiguity that requires the ::template syntax for dependent templates. typedef char no; struct yes { no dummy[2]; }; template<bool> struct conditional_declare; struct undeclared {}; template<> struct conditional_declare<true> { template<int> struct apply { void* value; friend void operator>(bool, const apply&) {} }; }; template<> struct conditional_declare<false> { static const int apply = 0; }; template<class T> yes is_declared(const T&); no is_declared(const undeclared&); undeclared local_function_bound_args; #define BOOST_LOCAL_FUNCTION_DECLARE_ARGS() \ conditional_declare<sizeof(is_declared(local_function_bound_args)) == \ sizeof(no)>::apply<0> local_function_bound_args int main() { BOOST_LOCAL_FUNCTION_DECLARE_ARGS(); // declares local_function_bound_args BOOST_LOCAL_FUNCTION_DECLARE_ARGS(); // turns into a pair of comparisons } In Christ, Steven Watanabe