2011/7/19 Edward Diener <eldiener@tropicsoft.com>
On 7/18/2011 4:04 AM, TONGARI wrote:
2011/7/18 Edward Diener <eldiener@tropicsoft.com

   On 7/17/2011 1:29 PM, Edward Diener wrote:

       On 7/17/2011 9:21 AM, TONGARI wrote:


           I'd like to have a macro like:


           which should expand to:

           struct a {};
           struct b: a {};
           struct c: a {};
           struct d: c {};
           struct e: c {};

           Is this possible at all?
           I have tried but with no luck, if this is impossible, please
           tell me so.

       I think you want above:


       This is a tuple with a possible second element as a seq. Each
       element of
       your seq is a tuple with the same rule as the top tuple.

       Following internal logic, perhaps with nested BOOST_PP_WHILEs, you
       should be able to cycle through each tuple and nested tuple
       forming the
       relationships you have created for your structs above. I can not
       guarantee this will be doable but at least you should have some
       idea of
       what to do from the description of what you have.

   I have to correct the above. The syntax for what I described must be:



I think I need the comma since I don't assume variadic macro.

I do not understand what you mean by that, and what some extra comma has to do with variadic macros

Without variadic macro we can just leave the 2nd arg empty (e.g. MACRO(x, ) where MACRO requires 2 args) as no derived classes.
I still do not have the above right. It should be:


IIUC, your surrounding ()s here are automatically packed by what I had:

#define PACK_2A( a1, a2 ) ((a1, a2)) PACK_2B
#define PACK_2B( a1, a2 ) ((a1, a2)) PACK_2A
#define PACK_2A_END
#define PACK_2B_END

and used like: BOOST_PP_CAT(PACK_2A children, _END)

BTW, if variadic macro available, they'd be

#define PACK_A( VARG... ) (( VARG )) PACK_B
#define PACK_B( VARG... ) (( VARG )) PACK_A
#define PACK_A_END
#define PACK_B_END


Just in case you do not know, you can use the Wave trace facility to see how your macros above are expanding when you invoke BUILD_HIERARCHY with your two parameters.

I used to use BOOST_PP_STRINGIZE to show me the result.
It turns out that BOOST_PP_SEQ_FOR_EACH cannot be used recursively.

...and I have to say I must give up on this temporarily, if I have time to back to this again, I'll see if Wave can help me figure out what happened.

Thanks for your patience.