code: public static ScalarOperation<Double> doubleMultiplicationOp() {
  		return new ScalarOperation<Double>(new ScalarFunction<Double>() {
  
  			@Override
  			public Double scale(Double a, double b) {
  				return a * b;
  			}
  
  		}, 1d);
  	}
docs: Builds the scaling operation for Doubles, that is the multiplying
  operation for the factor.
  
  @return {@link ScalarOperation} for Double