code: private double getDouble( int idx, double defaultValue, CssFormatter formatter ) {
          if( parameters.size() <= idx ) {
              return defaultValue;
          }
          return parameters.get( idx ).doubleValue( formatter );
      }
docs: Get the idx parameter from the parameter list as double.
  
  @param idx
  the index starting with 0
  @param defaultValue
  the result if such a parameter idx does not exists.
  @param formatter
  current formatter
  @return the expression