> i don't know if you're trying to be funny... > > but what's between the definition of N1 and the undef of A may be a very > complex. it's just simplified for demonstration.
It's not good programming practice to have a macro (in this case A) have two different values, with an #undef between then. There are very few good reasons to use #undef, but that's not one of them. The reason is that when you look at the usage of the macro and want to find how it's defined, a search for the definition may come up with the wrong one.
