I am doing some template meta programming, mostly just writing my own compile time list, but I also have some preprocessor magic which I want to use to make things easier if possible.
What I am trying to do is create a compile time list of functors. That part is done, but the macros to ease creation (and add to the list) are not.
An example in brief:
template<typename Functor, typename Tail>
struct node {
typedef Functor head;
typedef Tail tail;
};
template <typename Functor, typename Tail>
struct push_back {
typedef node<Functor, Tail> list;
};
struct unit0 {};
#define AUTO_FUNCTION(name) struct test_functor_##name { \
static void run_test(); \
}; \
typedef push_back< \
test_functor_##name, \
CONCAT(unit, PP_DEC(__COUNTER__)) \
>::list CONCAT(unit, __COUNTER__); \
void test_functor_##name::run_test()
AUTO_FUNCTION(hello) {
...
}
Now, this works because I have created a large set of preprocessor macros for PP_DEC, ie:
#define PP_DEC(x) PP_DEC_I(x)
#define PP_DEC_I(x) PP_DEC_ ## x
#define PP_DEC_1 0
#define PP_DEC_2 1
...
#define PP_DEC_N N
That's the part I really want to avoid and the reason I am asking this question. Does anyone have a suggestion on how I can use COUNTER without increasing its value, or some other way I can accomplish a counting pattern similar to:
0 1
1 2
2 3
...
Suggestions that change the semantics of push_back, etc. are of course also welcome :).
PS. This is not meant for production, only for fun. So GCC specific extensions are welcomed.
PPS. I am trying to avoid external dependencies, such as boost, as I want to understand everything I am doing (the whole point of this project).
