code: private void setRecursive(Type type, IAtomContainer mol) {
          switch (type) {
              case RECURSIVE:
                  this.type = type;
                  this.value = 0;
                  this.left = null;
                  this.right = null;
                  this.query = mol;
                  this.ptrn  = null;
                  break;
              default:
                  throw new IllegalArgumentException();
          }
      }
docs: Set the recursive value of this atom expression.
  
  @param type the type of expression
  @param mol  the recursive pattern