Ok will add the note. Yeah I know there might be some overhead involved and I actually was thinking about returning 0 (or non 0) depending on the outcome of parsing.
I decided to throw an Exception instead of returning an error code along with a default constructed AASequence() as I consider the alternative more prone to errors (e.g. if the user forgets to check the error code). Usually, I don't observe parsing errors so I guess it's not a good idea to generally construct a AASequence objects - no matter what comes. But I guess this is also a matter of taste. It's just that I prefer to fail early in the case of an invalid sequence.