That won't work because preprocessing is performed in a single pass. For example, consider the next code :
#define MYDEFINEWEIRD #define
MYDEFINEWEIRD N 6
int main() {
return 0;
}
After preprocessing, your code will looks like :
#define N 6
int main() {
return 0;
}
and "#define" is not a valid syntax on C or C++. Also, since the resulting preprocessor directive is not going to be processed, it won't resolve subsequent references to the "N" macro in your code.
Just for fun, you can call the preprocesor twice from the command line using g++/gcc. Consider the next code (define.cpp) :
#include <iostream>
#define MYDEFINEWEIRD #define
MYDEFINEWEIRD N 6
using namespace std;
int main() {
cout << N << endl;
return 0;
}
Then you can do:
$ g++ -E define.cpp | g++ -o define -x c++ - && ./define
and will output:
6