Re: Why 17 planes? (was: Re: Why 11 planes?)

On Tuesday 27 November 2012, Philippe Verdy <verdy_p_at_wanadoo.fr> wrote:

> This is not complicate to parse it in the foreward direction, but for the backward direction, it means that when you see the final low surrogate, you still need to rollback to the previous position: it can only be a leading high surrogate of the BMP, **or** (this is would be new) another low surrogate encoding, for which you must still get back to get the leading high surrogate. This requires a test if starting from a random position, but at least it remains possible to know where is the leading high surrogate.

Ah!

Does that mean that similar, or maybe worse, problems could arise with parsing in a reverse direction of the idea in the following post?

http://www.unicode.org/mail-arch/unicode-ml/y2011-m08/0307.html

A possible solution, should the need arise for more planes, would be to define one code point in plane 0 to have a meaning such as EXTRA SURROGATE and then one could have a sequence such as

HIGH SURROGATE, EXTRA SURROGATE, LOW SURROGATE

That mechanism could provide another 16 planes at a cost of one plane 0 code point.

Would that be a satisfactory solution to the problem?

William Overington

27 November 2012
Received on Tue Nov 27 2012 - 10:13:04 CST