"hellohello" "hello hello" 5 ['h', 'e', 'l', 'l', 'o'] ['α', 'β'] [] ['α', 'β', 'γ'] "αβγ" "αβγ" "αβγ" { byteIdx := 2 } ['α', 'β'] "αβa" "α α-" 'A' "aβγ" "abγ" "abc" "cbγ" "0bc" "01c" "012" "21c" "λbc" "abc-bc" "abc" "a\x00bb" 4 false true false false true true false true false "βγ" "γ" "αβγδ".toSubstring "abcd".toSubstring "abcd".toSubstring ["abc".toSubstring, "αβγ".toSubstring, "123".toSubstring, "".toSubstring] ["abc".toSubstring, "αβγ".toSubstring, "123".toSubstring, "".toSubstring] 'α' 'β' { byteIdx := 4 }