code: public VarDef addValue( VarValueDef value)
      {
      assert value != null;
  
      if( findValue( value.getName()) >= 0)
        {
        throw new IllegalStateException( "Value=" + value.getName() + " already defined for variable=" + getPathName());
        }
  
      values_.add( value);
      return this;
      }
docs: Adds a value definition for this variable.