Jorgen Schaefer scripsit:

> Just as an example, implementing a string API based on grapheme
> clusters (or abstract characters, which I think most people here
> mean) on top of codepoint vectors is not much of a problem.

The Unicode definition of "abstract character" is vague.  There is an
abstract character corresponding to each Unicode encoded character,
but there's no saying what other abstract characters may or may not
exist.  Consequently, an API based on abstract characters is a purely
abstract API.

Grapheme clusters have a sharp definition:  a grapheme cluster is a
single base character followed by zero or more nonspacing or enclosing
marks, or else a sequence of Hangul jamos constituting a single syllable.

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