C++ Macro Arithmetric
c++, macros
Solution
I haven't tested this, but should work:
#define SUBSTFOO3( a, b1, c1 ) foo1(a, b1, c1)
#define SUBSTFOO5( a, b1, c1, b2, c2 ) foo2(a, b1, c1, b2, c2)
/* ad nauseam */
#define foo( N, ... ) SUBSTFOO ## N ( __VA_ARGS__ )
This might also work:
#define SUBSTFOO3 foo1 /* no arguments needed */
#define SUBSTFOO5 foo2 /* "( __VA_ARGS__)" already the correct substitution */
#define foo( N, ... ) SUBSTFOO ## N ( __VA_ARGS__ )
Problem
I have to do with Macros (it's macros calling macros; so templates are out of the question). Here's what I want: ``` foo(3, a, b1, c1) --> foo1(a, b1, c1); foo(5, a, b1, c1, b2, c2) -> foo2(a, b1, c1, b2, c2); foo(7, a, b1, c1, b2, c2, b3, c3) -> foo3(a, b1, c1, b2, c2, b3, c3); ``` So basically, what I want is to be able to execute the "function" n -> (n-1)/2 at macro expansion time. Is this possible? [PS, if you dislike my questions; I support your right to downvote; my worst question so far is only -17, so maybe we can break that record; however, please let me know why my question is technically invalid.] EDIT: Foo takes a variable # of arguments, of the form: ``` foo(N, a1, b1, a2, b2, ... a_N, b_N) -> foo##N(a1, b1, a2, b2, ... a_N, b_N); ``` EDIT: To all the closers. This is a very different question. The former is about "how do I count the # of arguments in a Macro." (to which there was a good response on the mailing list). This question is a matter of: given I've counted the # of arguments, how do I dispatch on it?