Comment by esnard

You can find them all with this UnicodeSet query (though the query alone naturally won’t show you the lower and upper forms):

  [[:Changes_When_Lowercased:]&[:Changes_When_Uppercased:]]

It’s a handy way of finding all kinds of things along these lines. Look at the properties of some characters you care about, and see how you can add, subtract and intersect them.

TIL:

Polytonic orthography (from Ancient Greek πολύς (polýs) 'much, many' and τόνος (tónos) 'accent') is the standard system for Ancient Greek and Medieval Greek and includes:

- acute accent (´)

- circumflex accent (ˆ)

- grave accent (`); these 3 accents indicate different kinds of pitch accent

- rough breathing (῾) indicates the presence of the /h/ sound before a letter

- smooth breathing (᾿) indicates the absence of /h/.

Since in Modern Greek the pitch accent has been replaced by a dynamic accent (stress), and /h/ was lost, most polytonic diacritics have no phonetic significance, and merely reveal the underlying Ancient Greek etymology.

(https://en.wikipedia.org/wiki/Greek_diacritics)

The other day I posted similar tables/scripts for related character properties and there was some good discussion: https://news.ycombinator.com/item?id=42014045

- Unicode codepoints that expand or contract when case is changed in UTF-8: https://gist.github.com/rendello/d37552507a389656e248f3255a6...

- Unicode roundtrip-unsafe characters: https://gist.github.com/rendello/4d8266b7c52bf0e98eab2073b38...

For example, if we do uppercase→lower→upper, some characters don't survive the roundtrip:

Ω ω Ω

İ i̇ İ

K k K

Å å Å

ẞ ß SS

ϴ θ Θ

I'm using the scripts to build out a little automated-testing generator library, something like "Tricky Unicode/UTF-8 case-change characters". Any other weird case quirks anyone can think of to put in the generators?

The Unicode names of these 31 chars,

  LATIN CAPITAL LETTER D WITH SMALL LETTER Z WITH CARON

  LATIN CAPITAL LETTER {_} WITH SMALL LETTER {_}
    L,J
    N,J
    D,Z

  GREEK CAPITAL LETTER {ALPHA,ETA,OMEGA} WITH PROSGEGRAMMENI

  GREEK CAPITAL LETTER {ALPHA,ETA,OMEGA} WITH {PSILI,DASIA} AND {_}
    PROSGEGRAMMENI
    VARIA AND PROSGEGRAMMENI
    OXIA AND PROSGEGRAMMENI
    PERISPOMENI AND PROSGEGRAMMENI

What's the difference with letter Ch [0]? When it's capitalized at the beginning of the word, it also looks like uppercase C and lowercase h.

[0]https://en.wikipedia.org/wiki/Ch_(digraph)