Unicode equivalence: Difference between revisions

Revision as of 21:05, 25 April 2023

Revision as of 17:02, 29 August 2023

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The normal forms are not [[closure (mathematics)|closed]] under string [[concatenation]].<ref> Per [http://www.unicode.org/faq/normalization.html#5 What should be done about concatenation]</ref> For defective Unicode strings starting with a Hangul vowel or trailing [[Hangul Jamo (Unicode block)|conjoining jamo]], concatenation can break Composition.

However, they are not [[injective function|injective]] (they map different original glyphs and sequences to the same normalized sequence) and thus also not [[bijection|bijective]] (can'tcannot be restored). For example, the distinct Unicode strings "U+212B" (the angstrom sign "Å") and "U+00C5" (the Swedish letter "Å") are both expanded by NFD (or NFKD) into the sequence "U+0041 U+030A" (Latin letter "A" and combining [[ring above]] "°") which is then reduced by NFC (or NFKC) to "U+00C5" (the Swedish letter "Å").

A single character (other than a Hangul syllable block) that will get replaced by another under normalization can be identified in the Unicode tables for having a non-empty compatibility field but lacking a compatibility tag.