New submission from Frédéric Grosshans-André <frederic.grossh...@gmail.com>:
Currently (python 3.8.6, unidata_version 12.1.0) unicodedata.decomposition
outputs an empty string for hangul syllable (codepoints in the AC00..D7A3
range) while the decomposition is not empty: it is always two characters
(either a LV syllable and a T Jamo or a L jamo and a V jamo). This
decomposition is dedicible algorithmically (se §3.12 of Unicode Standard). A
python version of the algorithm is below (I don’t know C, so I can’t propose a
patch).
For each hangul syllable hs, I have used unicodedata.noramize to check that the
NFC of the decomposition is indeed hs, that the decomposition is two codepoints
long, that the NFD of both hs and the decompotsition coincide
def hangulsyllabledecomposition(c):
if not 0xAC00 <= ord(c) <= 0xD7A3 : raise ValueError('only Hangul syllables
allowed')
dLV, T = divmod(ord(c) - 0xAC00, 28)
if T!=0 : #it is a LVT syllable, decomposed into LV:=dLV*19 and T
return f'{0xAC00+dLV*28:04X} {0x11A7+T:04X}'
else : #it is a LVT syllable, decomposed into L , V
L, V = divmod(dLV,21)
return f'{0x1100+L:04X} {0x1161+V:04X}'
# Constants used:
# ==============
# 0xAC00 : first syllable == 1st LV syllable
# NB: there is one LV syllable every 28
codepoints
# 0xD7A3 : last Hangul syllable
# 0x1100 : first L jamo
# 0x1161 : first V jamo
# 0x11A7 : one before the 1st T jamo (0x1148), since T=0 means no trailing
#
# (all number below restricted for modern jamos where this algorithm is
relevant)
# 19 : Number of L jamos (not used here)
# 21 : Number of V jamos
# 28 : Number of T jamos plus one (since no T jamo for LV syllable)
----------
components: Unicode
messages: 391715
nosy: ezio.melotti, frederic.grosshans, vstinner
priority: normal
severity: normal
status: open
title: Add hangul syllables to unicodedata.decomposititon
versions: Python 3.8
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Python tracker <rep...@bugs.python.org>
<https://bugs.python.org/issue43925>
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