Question

On a software project (some old C compiler) we have a lot of variables which have to be saved normal and inverted.

Has somebody a idea how i can make a macro like that?

SET(SomeVariable, 137); 

which will execute

SomeVariable = 137; SomeVariable_inverse = ~137; 

Edit:

The best Solution seems to be:

#define SET(var,value) do { var = (value); var##_inverse = ~(value); } while(0) 

Thanks for the answers

Answer 1

One hazard I haven’t seen mentioned is that the ‘value’ macro argument is evaluated twice in most of the solutions. That can cause problems if someone tries something like this:

int x = 10; SET(myVariable, x++); 

After this call, myVariable would be 10 and myVariable_inverse would be ~11. Oops. A minor change to JaredPar’s solution solves this:

#define SET(var,value) do { var = (value); var##_inverse = ~(var); } while(0)