c++boostboost-preprocessor

Use Boost Preprocessor to Parse sequence of elements


I have a macro defined which is

#define TYPES (height,int,10)(width,int,20)

How to expand this macro using Boost Preprocessor something like this?

int height = 10;
int width = 20;

at most i am able to get is height,int,10 and width,int,20 as string but can't parse individual element.


Solution

  • Using BOOST_PP_VARIADIC_SEQ_TO_SEQ to turn TYPES into ((height,int,10))((width,int,20)) before processing, so that BOOST_PP_SEQ_FOR_EACH doesn't choke on it:

    #define MAKE_ONE_VARIABLE(r, data, elem) \
        BOOST_PP_TUPLE_ELEM(1, elem) BOOST_PP_TUPLE_ELEM(0, elem) = BOOST_PP_TUPLE_ELEM(2, elem);
    
    #define MAKE_VARIABLES(seq) \
        BOOST_PP_SEQ_FOR_EACH(MAKE_ONE_VARIABLE, ~, BOOST_PP_VARIADIC_SEQ_TO_SEQ(seq))
    

    Usage:

    #define TYPES (height,int,10)(width,int,20)
    
    int main() {
        MAKE_VARIABLES(TYPES)
    }
    

    Is preprocessed into:

    int main() {
        int height = 10; int width = 20;
    }
    

    See it live on Coliru