Re: Ada grammar rules for names too permissive?

[Jere <jhb.chat@gmail.com>]

On Thursday, January 3, 2019 at 5:05:34 PM UTC-5, Stephen Leake wrote:
> On Wednesday, January 2, 2019 at 12:47:22 PM UTC-8, Dmitry A. Kazakov wrote:
> > On 2019-01-02 20:21, Stephen Leake wrote:
> > > On Tuesday, January 1, 2019 at 12:42:36 PM UTC-8, Dmitry A. Kazakov wrote:
> > >> On 2019-01-01 20:49, Stephen Leake wrote:
> > >>> On Tuesday, January 1, 2019 at 12:44:17 AM UTC-8, Dmitry A. Kazakov wrote:
> > >>>> The grammar as written is never the one actually used for whatever
> > >>>> purpose other than explanation or, maybe, validation. An extreme case
> > >>>> illustrating why, is source code coloring,
> > >>>
> > >>> On the contrary, Emacs Ada mode source code coloring uses a generated parser for the Ada language, with only minimal changes from Annex P.
> > >>
> > >> In which case it should not work with syntactically incorrect programs.
> > > 
> > > No, it has error correction to deal with that.
> > 
> > Ada grammar contains no correction productions.
> 
> True for LRM Annex P, and also for Emacs ada.wy, but irrelevant. For LR parsers, there are error correction algorithms that do not require modifying the grammar. Emacs ada-mode uses the McKenzie algorithm (1); exploration of the parse table near the error location, combined with the redundancy of the Ada language (especially named blocks).
> 
> One of these days I'll have to write a paper on it ...
> 
> Meanwhile, it works quite nicely for me, and I'm waiting to hear from more people on how it works for them (a few positive responses so far, no negative).
> 
> (1) McKenzie, Bruce J., Yeatman, Corey, and De Vere,
>     Lorraine. Error repair in shift reduce parsers. ACM Trans. Prog.
>     Lang. Syst., 17(4):672-689, July 1995.

Is there a guide on how to manually update the Ada mode part of emacs?  I 
have a slightly older version, but it doesn't list ada mode in emacs
when I go through the normal update procedure.  I can't really update emacs
itself due to IT policies but was hoping to test out the newer Ada mode
fixes at some point.  In the version I have, it has trouble with things
like expression functions (situations where you have "is" but no "begin/end"
blocks).