I've run into a little theoretical problem. In a piece of code I'm maintaining there's a set of macros like
#define MAX_OF_2(a, b) (a) > (b) ? (a) : (b)
#define MAX_OF_3(a, b, c) MAX_OF_2(MAX_OF_2(a, b), c)
#define MAX_OF_4(a, b, c, d) MAX_OF_2(MAX_OF_3(a, b, c), d)
...etc up to MAX_OF_8
What I'd like to do is replace them with something like this:
/* Base case #1, single input */
#define MAX_OF_N(x) (x)
/* Base case #2, two inputs */
#define MAX_OF_N(x, y) (x) > (y) ? (x) : (y)
/* Recursive definition, arbitrary number of inputs */
#define MAX_OF_N(x, ...) MAX_OF_N(x, MAX_OF_N(__VA_ARGS__))
...which, of course, is not valid preprocessor code.
Ignoring that this particular case should probably be solved using a function rather than a preprocessor macro, is it possible to define a variadic MAX_OF_N() macro?
Just for clarity, the end result should be a single macro that takes an arbitrary number of parameters and evaluates to the largest of them. I've got an odd feeling that this should be possible, but I'm not seeing how.