double r2 
   (/*args*/  x ,  y ,  z  ) {
    return 
    plus 
  ( power 
  ( x, 2 )
  , power 
  ( y, 2 )
  , power 
  ( z, 2 )
   )
  
  ;} //end of lambda
  


    // test="ci and not(set)"
   
    double  d2  ;
   



class  sphere 
 : public math::Set<math::R3> {
  public:
     
  bool condition ( x, y, z ){
  return eq 
  (  r2  
  ( x, y, z )
  , d2 )
  ;} //end of condition
 
  };
 


 d2 =  2.1  ;
 


    // test="ci and not(set)"
   
math::Set<math::R3>*  mySphere  = new  sphere  ;