template<class IntervalT > 
struct continuous_type {
  // types
  typedef IntervalT::domain_type                        domain_type;
  typedef boost::call_traits< domain_type >::param_type DomainP;    

  // public static functions
  static bool open_bound_less_equal(DomainP, DomainP) ;
  static bool open_bound_less(DomainP, DomainP) ;
};