Re: Simple case mapping and normalization

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Tim Greenwood asked:

> I see from section 5.18 of TUS that normalization, and in particular
> NFC is not guaranteed to be preserved after a case conversion
> operation. Is this still true if only the simple uppercase or simple
> lowercase from UnicodeData.txt is used instead of the full case
> mapping?

Yes.

> If not can someone provide an example.

I assume you mean "If so..."

Here is an example:

<004A, 030C> is in NFC. (Capital letter J with a combining hacek)

If I use a simple lowercase transform on that I get:

<006A, 030C> That is not in NFC, because NFC(<006A, 030C>) --> 01F0

I think you can also get into trouble with combining marks
applied to capital Greek rho (cf. 1FE4) and possibly the
Latin long-s, too.

In other words, there are a few edge cases where there are
not completely symmetrical one-to-one simple case mappings between
some precomposed characters with diacritics.

--Ken

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