code: public static MutableLongTuple multiply(
          LongTuple t0, long factor, MutableLongTuple result)
      {
          return LongTupleFunctions.apply(
              t0, (a)->(a*factor), result);
      }
docs: Multiply the given input tuple with the given factor, and
  store the result in the given result tuple.
  
  @param t0 The input tuple
  @param factor The scaling factor
  @param result The tuple that will store the result
  @return The result tuple
  @throws IllegalArgumentException If the given tuples do not
  have the same {@link Tuple#getSize() size}