Re: [PATCH] Unicode Lisp reader escapes

[Richard Stallman <rms@gnu.org>]

     > Regarding \u: the question is whether an Emacs escape for Unicode
     > characters should be compatible with C string syntax for Unicode
     > characters, or coherent with the Emacs \x escape.

    The thing with the Emacs \x escape is that anyone using it for characters
    outside of ASCII is asking for pain, and always has been. It has only ever
    been clearly defined for that character set; any existing code in the
    repository for other characters, for example, _will definitely_ break with
    the merging of the Unicode branch.

We are miscommunicating.  Whether it is wise to use \x is not the
question.  The issue I am talking about is that of _coherence_
(parallelism of syntax) between \x and \u.

     > I think one relevant question is to what extent the C and Emacs Lisp
     > string syntax are compatible in the first place.  Emacs Lisp string
     > syntax was largely based on C string syntax in 1984, but I don't know
     > how C has developed since 1990.  Can someone report on this question?

    The \u syntax (with a fixed number of digits) came into wide use with Java
    in 1996. The necessity for the \U extension arose with progress towards
    version 3.0 of Unicode and its ~1.1 million available code points. That
    version of the standard was released in 1999; the C99 ISO standard for C of
    the same year included both \u and \U. Various other C-oriented programming
    languages have incorporated the syntax since. 

Thank you, but my question here is not about \u.  Rather, it is about
whether there are OTHER incompatibilities between Emacs Lisp and C
string syntax.

I want to see that information before deciding what to do here.