On 10/02/11 15:59, Lorenzo Caminiti wrote:
On Mon, Feb 7, 2011 at 11:08 AM, Lorenzo Caminiti <lorcaminiti@gmail.com> wrote:
On Sun, Feb 6, 2011 at 10:26 AM, Vicente Botet <vicente.botet@wanadoo.fr> wrote:
The fact that you can not use variadic macros at work doesn't means that your library can not provide in addition variadic macros on compilers supporting them. I have no idea the work that this suppose, but if the interface could be more appealing your library will have much more people interested in.
Have you an idea of how the interface could be simplified if variadic macros were used?
Hello all,
Based on some prototyping that I have done so far, I think I can simplify the local function macro syntax as follows using C99 variadics:
void BOOST_LOCAL_FUNCTION_PARAMS(int x, double y, // [1] bind a, bind& b, const bind c, const bind& d) { ... } BOOST_LOCLA_FUNCTION_NAME(f) f(1, 1.23);
** Note that there are NO extra parenthesis!! :-)) ** What do you think? Is this simple enough?
Amazing! (I might argue that the parentheses around "f" are extra, but that would be churlish ;)) <snip>
The above macros have the important advantage of using NO extra parenthesis on C99 but they also have the following (small?) limitations:
1) They do not allow the local function to recursively call itself (because the function name is not specified until after the body is programmed so it is not available within the body for recursive calls). 2) They always require the use of Boost.Typeof to deduce the function result type (the library already requires Boost.Typeof for variable binding anyways).
You shouldn't need to use Typeof if you extract the return type in the manner Steven Watanabe suggested: #include <boost/mpl/assert.hpp> #include <boost/type_traits/function_traits.hpp> #include <boost/type_traits/is_same.hpp> #define EXTRACT_TYPE_BEFORE \ deduce_result(); \ typedef boost::function_traits< \ typeof(deduce_result)>::result_type result_type; int main() { void EXTRACT_TYPE_BEFORE BOOST_MPL_ASSERT((boost::is_same<result_type, void>)); } It even gives a (relatively) nice error when the user forgets the return type (on gcc 4.4): ‘deduce_result’ was not declared in this scope I share your hope that this syntax is enough to satisfy most of the objectors! Do check how they respond when misused, though; a little effort to improve error messages might go a long way. John