Re: On language-dependent defaults for character-folding

[Eli Zaretskii]

> From: Richard Stallman <address@hidden>
> CC: address@hidden, address@hidden, address@hidden
> Date: Tue, 23 Feb 2016 12:43:56 -0500
> 
> That is interesting.  It means we need several levels of folding:
> 
> * Different appearances of the same letter+decorations:
>   as a single code point, or as a composition.
> 
> * Identical-looking distinct code points (Latin a and Cyrillic a).

This one is a very specialized feature needed only in some marginal
use cases (like looking for the so-called "confusables" -- characters
that look the same and could be used for deception, e.g. in URLs).

> * The same letter with different decorations (o and ö in English).
> 
> * Equivalent letters (ö and ø in Swedish).

Not just letters -- sequences of characters.  For example, å vs aa in
Danish, or ffi vs ffi.

> Is there any need, ever, to disable the first level?

One could imagine a use case when you want to find only precomposed
characters, not their decomposed equivalents.  But it should be rare
indeed.

> The other levels are language-specific, and the user might want to
> enable or disable them.

Not all of them are language-specific.  Some are valid in any
language.