[NNTP] wildmat-exact

[Charles Lindsey]

In <1gw5yas.10gs6ua41nlw0M%pmrobinson at gmx.net> pmrobinson at gmx.net (Peter Robinson) writes:

>Charles Lindsey said:
>> In <20050505085035.GE57289 at finch-staff-1.thus.net>
>> "Clive D.W. Feather" <clive at demon.net> writes:
>> 
>> >Charles Lindsey said:
>> >> In draft26.pre-1.txt I find
>> >> 
>> >>      wildmat = wildmat-pattern *("," ["!"] wildmat-pattern)
>> >>      wildmat-pattern = 1*wildmat-item
>> >>        ; must not begin with "!" if not immediately preceded by "!"
>> >>      wildmat-item = wildmat-exact / wildmat-wild
>> >>      wildmat-exact = %x21-29 / %x2B / %x2D-3E / %x40-5A / %x5E-7E /
>> >>           UTF8-non-ascii ; exclude * , ? [ \ ]
>> >>      wildmat-wild = "*" / "?"
>> >> and
>> >>      newsgroup-name = 1*wildmat-exact

>> Suppose, for the sake of argument, that '!' were a permitted character in
>> newsgroup-names (despite prohibitions to the contrary in RFC 1036 and
>> Usefor). Then the following newsgroup-names could legitimately exist.
>> 
>> 
>> So the wildmat "!foo.bar" matches "!foo.bar", "foo.baz" and "bar.foo", and
>> "!!foo.bar" matches "foo.bar", "foo.baz" and "bar.foo". You can have great
>> fun working out other interesting effects.

>Actually, assuming the disambiguating comment was normative, neither of
>those are valid wildmats according to this spec.  You'd have to have
>something like "a,!foo.bar" and "a,!!foo.bar".  Is there a good reason
>why we don't have the following: ?

>        wildmat = ["!"] wildmat-pattern *("," ["!"] wildmat-pattern)
>                  ^^^^^

I believe the disambigating comment was intended to be normative (and if
it wasn't and if it stays, then that would need to be fixed).

You are right about my examples being invalid, but similar absurdities
would arise with the forms "a,!foo.bar" and "a,!!foo.bar", and it is still
not possible to write a wildmat that would accept just the single group
"!foo.bar".

As to allowing a '!' before the first comma, the intention was evidently
to establish the universe within which the exclusions were then to be
made. It fails to do so, of course, because if you want the effect of "all
non-comp.* groups", you can still write "*,!comp.*", even if you cannot
write "!comp.*". However, the former makes it clearer to the human reader
what you are trying to do, so I have no wish to change it.

>As things stand (wildmat as it is, the comment just a comment) I'd say
>both your examples are legal and unambiguous but don't mean what you
>wanted them to mean (they match exactly 1 and 0 groups respectively).


>> Life would be simpler if '!' was simply excluded from wildmat-exact.

>I agree.

OK, that makes two of us. But we need some more players ...

-- 
Charles H. Lindsey ---------At Home, doing my own thing------------------------
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