Here is the tranformation done by the preprocessor: https://gist.github.com/matt-42/a53cc0b0a8d8f1cf673f

It would be really convenient to have it done by the C preprocessor, but it seems impossible to me to get it with macro only. Am I wrong?

It seems like you could do something like:

    #define IOD_SYM(name) iod_define_symbol(name, _##name);
    #define S(name) s::_##name;

Then use S(test) instead of @test and any files that need these symbols defined could just have IOD_SYM(test) at the top or something.

#define S(name) is a bit dangerous. It would affect any C/C++ function called S.

Actually using [ZLang](https://github.com/pfultz2/ZLang), you could define them like this:

    #define IOD_DEFINE_SYMBOL(name) iod_define_symbol(name, _##name)
    #define IOD_S(name) s::_##name

    #define ZLANG_iod_define (IOD_DEFINE_SYMBOL)
    #define ZLANG_iod_s (IOD_S)

And then compiling with `-DZLANG_NS=iod` you can call it like this:

    // Define symbols
    $(define hello)
    $(define message)

    auto hello_api = make_api(

        // The hello world procedure.
        $(s hello) = [] () { return D($(s message) = "Hello world."); }

    );

Also, ZLang can be supported without a need for a dependency on ZLang.