Sure. "a" alone is a valid default grapheme cluster. Combining dieresis alone is
a perfectly valid default grapheme cluster. 2 if separate, but one if
concatenated (in the right order). This is similar (though not completely) to
the case of words: "large fisher" contains two words; so does "man is", but when
concatenated they only form 3 words.
Thank you. I was supposing that isolated combining marks were considered in some way defective, much as (at least according to some people) XML is treating them, and so either illegal or deprecated.
Well, I can see that what you have done in ICU/Java is actually more useful, and that is the kind of interface I had in mind.Note that combining dieresis is *very* much different than the case of surrogate code points. D800 has no sensible independent existence: combining dieresis certainly does.
That's one reason why we in ICU / Java chose an iteration interface for entities like this. You can find a boundary, or you can find the next or previous one (or nth). No general guarantees that concatenation will preserve the number -- or relative placement -- of boundaries. That's because the determination of boundaries is context-dependent. The same goes for line boundaries; look at TR#11.
You could conceivably restrict your dream programming language to only
'complete' default grapheme clusters, defined as those where the addition of
previous characters would never change that boundary, but in practice I don't
think your dream language would be particularly useful at, well, actual
programming.
To go back closer to where we started, I would suggest that if people are working with Unicode primarily at that level (of lack of enlightenment concerning implementation details), then they should not be asking questions like "is this string normalised?", and when they ask "how many characters in this string" they should expect an answer in terms of default grapheme clusters rather than code units or code points. They shouldn't hack into lower levels unless they need to. And this is effectively the level at which I was seeing C7-C9 operating re "interpretation".
-- Peter Kirk [EMAIL PROTECTED] (personal) [EMAIL PROTECTED] (work) http://www.qaya.org/
