Re: Corrigendum #9

From: Asmus Freytag <>
Date: Sat, 31 May 2014 19:15:52 -0700

On 5/31/2014 12:36 PM, Philippe Verdy wrote:
> May be; but there's real doubt that a regular expression that would
> need this property would be severely broken if that property was
> corrected. There are many other properties that are more useful (and
> mich more used) whose associated set of codepoints changes regularly
> across versions.

we have learned that there are always more implementations of a feature
than we might have predicted. That has been true, for Unicode, from day one.

More importantly, while a regex that uses an expression that is
equivalent to "IsInArabiPresentation(x)" may or may not be well-defined,
there is no reason to break it by splitting the block.

As blocks cannot be discontiguous (unlike other properties), some Arabic
Presentation forms would have to be put into a new block (Arabic
Presentation Forms C). This is what would break such expressions - it
has, in fact, nothing to do with the status of the noncharacters.

There's no reason to contemplate breaking changes of any kind at this point.


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