CODEWITHSUNDEEP
unicodeunicode-normalization
Jonas Schäfer
Jonas Schäfer

Reputation: 20718

Why do LATIN SMALL LETTER DOTLESS I, COMBINING DOT ABOVE not get normalized to "i" in NFC form?

Example in Python:

>>> s = 'ı̇'
>>> len(s)
2
>>> list(s)
['ı', '̇']
>>> print(", ".join(map(unicodedata.name, s)))
LATIN SMALL LETTER DOTLESS I, COMBINING DOT ABOVE
>>> normalized = unicodedata.normalize('NFC', s)
>>> print(", ".join(map(unicodedata.name, normalized)))
LATIN SMALL LETTER DOTLESS I, COMBINING DOT ABOVE

As you can see, NFC normalization does not compose the dotless i + a dot to a normal i. Is there a rationale for this? Is this an oversight? Or is it not included because NFC is supposed to be the perfect inverse of NFD (and one wouldn’t want to decompose i to dotless i + dot).

Upvotes: 3

Views: 310

Answers (1)

nwellnhof
nwellnhof

Reputation: 33638

While NFC isn't the "perfect inverse" of NFD, this follows from NFC being defined in terms of the same decomposition mappings as NFD. NFC is basically defined as NFD followed by recomposing certain NFD decomposition pairs. Since there's no decomposition mapping for LATIN SMALL LETTER I, it can never be the result of a recomposition.

Upvotes: 3

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