Re: [Boost-users] [preprocessor]:issues with expansion.

Date: Wed, 19 Dec 2012 20:13:23 -0800 From: jeffrey.hellrung@gmail.com To: boost-users@lists.boost.org Subject: Re: [Boost-users] [preprocessor]:issues with expansion.

On Wed, Dec 19, 2012 at 3:58 PM, Littlefield, Tyler mailto:tyler@tysdomain.com> wrote: hello all: I have the following code: #define REGISTER_MODULE(module)(\ #ifdef BOOST_PP_EQUAL(BOOST_PP_LIST_SIZE(MODULES), 0)\ //there are currently no modules in the list. #define MODULES((module), BOOST_PP_NIL) #else BOOST_PP_LIST_APPEND(MODULES, module)\ #endif )

I am somewhat of a newb at preprocessor magic, so any advice would be useful. For whatever reason this translates out to 'module)' when I try to compile it with -E -P. The idea is that it will add to the modules list (assuming the modules list exists) the module to be registered, which should just be a type. Thanks,

Someone can correct me here, but I believe you can't use preprocessor directives (#define, #if, etc.) within a macro definition, and, well, who knows what'll happen if you try :/

- Jeff

Right, and to address your desired use case a little more specifically, I don't think you can store state in the preprocessor in between macro invocations (if I'm wrong, please correct me, I would find such an ability very useful as well). Regards, Nate