How to use an array index as an operator?

Question

How to use an array index as an operator?

Such that:

#include

main()
{
    char sign[]={\'+\',\'-\'};
    int a, b;
    a = 12 sign[1] 10         


        

Answer 1

I'd be tempted to use a ternary for this:

a = 12 + (sign[1] == '-' ? -1 : +1) * 10;

Of course this defaults to + but you could introduce earlier checks to guard against that.

You could use this to form a macro:

12 + SIGN(1) 10;

with

#define SIGN(s) (sign[(s)] == '-' ? -1 : +1) *

which recovers the form of the expression in your question excepting the square brackets.