How can I make a variable always equal to the result of some calculations?

Question

In math, if z = x + y / 2, then z will always change whenever we replace the value of x and y. Can we do that in programming

Answer 1

You can get what you're asking for by using macros:

{
    int x, y;
#define z (x + y)
    /* use x, y, z */
#undef z
}

The #undef is for a little sanity. For more sanity, don't use macros at all, and go with one of the other answers, and deal with the extra verbosity.

Although a class with a custom operator int would work in a lot of cases ... hmm.