defproc arbiter (bool a, b, u, v)
{
  bool _u, _v;
  prs {
   [keeper=0]  a &  _v -> _u-
   [keeper=0] ~a  | ~_v  -> _u+
   [keeper=0]  b &  _u -> _v-
   [keeper=0] ~b  | ~_u  -> _v+
   [keeper=0] _u  => u-
   [keeper=0] _v => v-
  }
  spec {
    mk_excllo(_u, _v)
  }
}


arbiter a;
