From: Philippe Verdy (email@example.com)
Date: Tue May 13 2008 - 12:52:49 CDT
Russ Stygall wrote:
> From UnicodeData.txt, 'prosgegrammeni' is equated to 'small letter iota',
Note: Unicode does not "equate" characters, it defines canonical and
compatibilty equivalence mappings and string canonicalization processes;
canonical equivalence is based on those mappings, but it does not mean that
the characters are "equal".
> 1FBE;GREEK PROSGEGRAMMENI;Ll;0;L;03B9;;;;N;;;0399;;0399
> 03B9;GREEK SMALL LETTER IOTA;Ll;0;L;;;;;N;;;0399;;0399
> From the Greek Extended table, see below, the following three characters
> to ALPHA/ETA/OMEGA plus 0345, not plus 1FBE or even 03B9!
> 1FBC;GREEK CAPITAL LETTER ALPHA WITH PROSGEGRAMMENI;Lt;0;L;0391
> 1FCC;GREEK CAPITAL LETTER ETA WITH PROSGEGRAMMENI;Lt;0;L;0397
> 1FFC;GREEK CAPITAL LETTER OMEGA WITH PROSGEGRAMMENI;Lt;0;L;03A9
> Why is 'iota subscript' (below) used as a substitute for 'iota adscript'
in the above cases?
> 0345;COMBINING GREEK YPOGEGRAMMENI;Mn;240;NSM;;;;;N;*;;0399;;0399
Both U+1FBE and U+03B9 are spacing characters, not combining characters, the
equivalence between them considers this because U+1FBE is effectively an
adscript, and definitely not a subscript; the letters with iota subscripts
are different; Note that the iota adscript is not necessarily below the
baseline, in fact in many texts it appares on the baseline as well and when
capitalized it is treated like a standard iota and still becomes a capital
U+1FBE is then just a minor graphic variant of a regular iota letter and not
even guaranteed to be different. On the opposite the combining subscript
does not change when the text is capitalized.
What can be said is that U+1FBE (the iota adscript) is a compatibility
character provided only for roundtrip compatibility with other encodings;
the name may be misleading, for you but "ypogegrammeni" (the combining
subscript iota) is NOT equivalent to "prosgegrammeni" (the non-combining
small letter iota that normally follows another letter but may be treated as
a plain letter itself).
The character names for U+1FBC, U+1FCC and U+1FFC are misleading you, but
this does not change the encoding and expected properties which look
correct; the confusion may be the result of the evolution of the Greek
orthography, where the distinctive subscripts have become adscripts over
time (that are no longer distinctable from plain letters). But such
evolution of orthography does not make these iota equivalent: a nchange of
orthography is still considered as a significant distinction.
> The character 1FBE, in the Greek Extended table of Unicode 5.0, is
> below the base line, and appears as if it is 0020+0345
U+1FBE prosgegrammeni is not necessarily below the baseline (this is a
possible graphic distinction, but it is not mandatory); however, in any
case, it will never be below another letter or other character.
It is definitely not equivalent to space+ypogegrammeni, and can appear in
the middle of words like a normal letter without being considered as a
symbol and without introducing any word break opportunity.
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