Subtract the specified rhs from the value of the specified lhs as described by IEEE-754 and return a reference to this object.
* If rhs is signaling NaN, then store the value of the macro EDOM into errno and return a NaN. * Otherwise if rhs is NaN, then return a NaN. * Otherwise if rhs is infinity, then return infinity. * Otherwise if subtracting rhs from lhs object's value results in an absolute value that is larger than std::numeric_limits<Decimal128>::max() then store the value of the macro ERANGE into errno and return infinity with the same sign as that result. * Otherwise return the result of subtracting the value of rhs from the number lhs.