From: Tanaka Akira <akr@...>
Date: 2013-07-18T18:07:26+09:00
Subject: [ruby-core:56073] Re: [ruby-trunk - Bug #8653][Open] Unexpected result of String#succ with utf-16 and utf-32 string.

2013/7/18 phasis68 (Heesob Park) <phasis@gmail.com>:
> Bug #8653: Unexpected result of String#succ with utf-16 and utf-32 string.
> https://bugs.ruby-lang.org/issues/8653

> I found the result of String#succ of UTF-16LE encoded string is incorrect.
>
> As a result, Range of UTF-16LE encoded string show some unexpected behavior.

I don't say the bahavior is incorrect.

  % ruby -e 'p "A".encode("UTF-16LE").force_encoding("ASCII-8BIT")'
  "A\x00"
  % ruby -e 'p "A".encode("UTF-16LE").succ.force_encoding("ASCII-8BIT")'
  "A\x01"
  % ruby -e 'p "B".encode("UTF-16LE").force_encoding("ASCII-8BIT")'
  "B\x00"
  % ruby -e 'p "B".encode("UTF-16LE").succ.force_encoding("ASCII-8BIT")'
  "B\x01"

String#succ generates the bytewise lexicographicaly next characters
successfully.

I agree that is not intuitive.
But it is very difficult to define String#succ in encoding neutral way.
-- 
Tanaka Akira