Category "letter"

How to detect letters and theirs upper/lower case format from two characters which need to be compared to each other?

I need to get: If either of the characters is not a letter, return -1 If both characters are the same case, return 1 If both characters are letters, but not the

RealmDB and diacritical letters problem with upper and lower case

I have project where I use RealmDB. When I use search feature with normal string(letters) it work well - upper/lower letters are in mode Case.INSENSITIVE, but i