Boolean Expressions

De Morgan's rules
Convert expression into range membership
Disjunctive expression:
                if (i <= 0 || i > 256) {

conversion into conjunction:
    i <= 0 || i > 256  <=>
    !(!(i <= 0) && !(i > 256)) <=>
    !(i > 0 && i <= 256) <=>
    !(0 < i && i <= 256) <=>
Short-circuit evaluation
- Conjunction:
  if (t != NULL && t->type != TEOF && interactive && really_exit)
  really_exit = 0;
- Disjunction:
  if (argv == NULL || argv[1] == NULL || argv[2] == NULL)
  return -1;