> [I sent this message a few weeks ago but did not get a response.
> Could we get the discussion moving again?]
>
>     > I am not sure whether that relates to the suggestion I made:
>
>     >> I think that if we wrote a separate regexp for each kind of grep,
>     >> all together they would match a lot fewer different strings than the
>     >> current regexp does, and they would be much easier to understand.
>
>     Indeed, the two do not conflict.  I.e. I think there's no problem with
>     compile.el's current behavior in this regard and I believe your suggestion
>     w.r.t grep.el should work just fine.
>
> Would someone like to try implementing this?
> (Please respond to this message, if so.)

Perhaps what is needed to start with is to ask people to send output
examples of different kinds of grep.  We could put these example in a
new file etc/grep.txt similarly to etc/compilation.txt.

I've collected a few examples in the file attached below.  The section
`grep ???' contains examples deduced from regexps in `grep-regexp-alist'.
Could someone recognize what grep produces them?

Also you can see that with recent changes in GNU grep CVS it produces
escape sequences not handled by grep.el.  This requires a separate rule
in `grep-regexp-alist'.