tonyg

      ws = *(
              %x20 /              ; Space
              %x09 /              ; Horizontal tab
              %x0A /              ; Line feed or New line
              %x0D )              ; Carriage return

  struct nonzero_t {
    int is_negative;
    unsigned int one_less_than_the_absolute_value;
  };

  data Nat = Z | S Nat
  data NonZeroNat = OnePlus Nat
  data NonZeroInt = Negative NonZeroNat | Positive NonZeroNat