Method add

gecode/int/view-val-graph/bi-link.hpp:58–62

  }

  forceinline void
  BiLink::add(BiLink* l) {
    l->_prev = this; l->_next = _next;
    _next->_prev = l; _next = l;
  }
  forceinline void
  BiLink::unlink(void) {
    BiLink* p = _prev; BiLink* n = _next;