Issue: PATHNAME-EXTENSIONS (Version 1)

[David A. Moon <Moon@STONY-BROOK.SCRC.Symbolics.COM>]

The examples only shed negative illumination for me.  That is,
I'm not sure what precisely "special meaning", "something weird",
not "nice values", and "hairy junk" really mean.  I suspect part of
what you're worried about is wildcard pathnames; wasn't there already
proposed a PATHNAME-WILD-P (or was it WILD-PATHNAME-P?) function for
that?

In one of your examples COMMON-PATHNAME-P seems to mean "this pathname
is acceptable to the host" and in the other example COMMON-PATHNAME-P
seems to mean "this pathname is acceptable to a particular user-written
algorithm".  To me those don't seem to be the same test.  I think the
former test makes sense to codify as a function (although when I try
to articulate precisely what "acceptable" means, I have trouble; can it
be dynamically varying depending on what files and directories currently
exist?), but I don't see that your proposed function does this test.
The latter test seems hard to specify without saying anything about
the user-written algorithm.

I'm not really opposed to this, but I don't think it's defined
specifically enough yet.  I begin to fear that it is inherently
impossible to define it specifically enough.