需要帮助，将可变参数宏扩展为一系列字符串化名称和值

Question

I know in C++ I can get the name of a macro parameter using the # directive, like so:

#define FOO(value) #value

What I'm trying to figure out is how to convert a list of parameters into a longer list that includes stringified names as well. Given FOO(a, b, a+b) I want to get "a", a, "b", b, "a+b", a+b .

I can do this by creating N macros for potential sequences of up to N parameters, but is there a way to write this with variadic macros?

Answer 1

Yes, you can use BOOST_PP_ENUM to iterate over the variadic data and add commas between each expansion:

#define FOO(...)                                \
    BOOST_PP_ENUM(                              \
        BOOST_PP_VARIADIC_SIZE(__VA_ARGS__),    \
        MACRO,                                  \
        BOOST_PP_VARIADIC_TO_TUPLE(__VA_ARGS__) \
    )

#define MACRO(z, n, data) \
    BOOST_PP_STRINGIZE(BOOST_PP_TUPLE_ELEM(n, data)), BOOST_PP_TUPLE_ELEM(n, data)

FOO(a, b, a+b) //"a", a , "b", b , "a+b", a+b

ENUM takes a count of iterations, a macro, and data to give to the macro. We pass a PP tuple containing the variadic data. The macro then accesses the element with index n . You can see this work here .