code: public Decimal plus(Decimal augend) {
          if ((this == NaN) || (augend == NaN)) {
              return NaN;
          }
          return new Decimal(delegate.add(augend.delegate, MATH_CONTEXT));
      }
docs: Returns a {@code Decimal} whose value is {@code (this + augend)},
  with rounding according to the context settings.
  @param augend value to be added to this {@code Decimal}.
  @return {@code this + augend}, rounded as necessary
  @see BigDecimal#add(java.math.BigDecimal, java.math.MathContext)