Possible bug in formal grammar for extended grapheme cluster

[David P. Kendal via Unicode]

Hi,

It’s possible I’m missing something, but the formal grammar/regular
expression given for extended grapheme clusters appears to have a bug
in it.
<https://unicode.org/reports/tr29/#Table_Combining_Char_Sequences_and_Grapheme_Clusters>

The bug is here:

    RI-Sequence := Regional_Indicator+

If the formal grammar is intended to exactly match the rules given the
the “Grapheme Cluster Boundary Rules” section below it as-is, then
this should be

    RI-Sequence := Regional_Indicator Regional_Indicator

since as given it would cause any number of RI characters to coalesce
into a single grapheme cluster, instead of pairs of characters. That
is, the text U+1F1EC U+1F1E7 U+1F1EA U+1F1FA would represent one
grapheme cluster instead of the correct two.

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dpk (David P. Kendal) · Nassauische Str. 36, 10717 DE · http://dpk.io/
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