Re: [precis] Applying the rules three times to get a stable output string?

William Fisher <william.w.fisher@gmail.com> Sat, 09 December 2017 19:34 UTC

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From: William Fisher <william.w.fisher@gmail.com>
Date: Sat, 9 Dec 2017 12:34:02 -0700
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To: Christian Schudt <christian.schudt@gmx.de>
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Subject: Re: [precis] Applying the rules three times to get a stable output string?
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Where it makes a difference for NicknameCaseMapped:

"\u210c"
"\u20a8"

Where it makes a difference for Nickname due to spaces:

"\u00a8"
"\u02dc"


On Sat, Dec 9, 2017 at 8:37 AM, Christian Schudt
<christian.schudt@gmx.de> wrote:
> Hi,
>
> RFC 8264 introduced these new sentences:
>
>    under certain circumstances, such as when Unicode
>    Normalization Form KC is used, performing Unicode normalization after
>    case mapping can still yield uppercase characters for certain code
>    points
>
>    Therefore, an implementation SHOULD apply the rules
>    repeatedly until the output string is stable
>
>
> I could imagine these sentences refer to code points of the „Unstable“ category, but this category is unused.
>
> Are there any concrete code points or input strings which show this unstable behaviour?
> I am asking for some test vectors, i.e. an input string, which doesn’t have the expected output string after the first rule application, but after the second one.
>
> Thanks,
> — Christian
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