develooper Front page | perl.perl6.language | Postings from May 2005

Re: comprehensive list of perl6 rule tokens

Thread Previous | Thread Next
From:
Jeff 'japhy' Pinyan
Date:
May 25, 2005 07:56
Subject:
Re: comprehensive list of perl6 rule tokens
Message ID:
Pine.LNX.4.61.0505251052280.14648@perlmonk.org
On May 25, Mark A. Biggar said:

> Jonathan Scott Duff wrote:
>> On Tue, May 24, 2005 at 11:24:50PM -0400, Jeff 'japhy' Pinyan wrote:
>> 
>>> I wish <!prop X> was allowed.  I don't see why <!...> has to be confined to 
>>> zero-width assertions.
>> 
>> I don't either actually. One thing that occurred to me while responding
>> to your original email was that <!foo> might have slightly wrong
>> huffmanization.  Is zero-width the common case?  If not, we could use
>> character doubling for emphasis:  <!foo> consumes, while <!!foo> is
>> zero-width. 
>
> Now <prop X> is a character class just like <+digit> and so
> under the new character class syntax, would probably be written
> <+prop X> or if the white space is a problem, then maybe <+prop:X>
> (or <+prop(X)> as Larry gets the colon :-), but that is a pretty
> adverbial case so ':' maybe okay) with the complemented case being
> <-prop:X>.  Actually the 'prop' may be unnecessary at all, as we know
> we're in the character class sub-language because we saw the '<+', '<-'
> or '<[', so we could just define the various Unicode character property
> codes (I.e., Lu, Ll, Zs, etc) as pre-defined character class names just
> like 'digit' or 'letter'.

Yeah, that was going to be my next step, except that the unknowing person 
might make a sub-rule of their own called, say, "Zs", and then which would 
take precedence?  Perhaps <prop:X> is a good way of writing it.

> BTW, as a matter of terminology, <-digit> should probably be called the
> complement of <+digit> instead of the negation so as not to confuse it with 
> the <!...> negative zero-width assertion case.

Yeah, I just wrote that in my recent reply to Scott.  I realized the 
nomenclature would be a point of confusion.

-- 
Jeff "japhy" Pinyan         %  How can we ever be the sold short or
RPI Acacia Brother #734     %  the cheated, we who for every service
http://japhy.perlmonk.org/  %  have long ago been overpaid?
http://www.perlmonks.org/   %    -- Meister Eckhart

Thread Previous | Thread Next


nntp.perl.org: Perl Programming lists via nntp and http.
Comments to Ask Bjørn Hansen at ask@perl.org | Group listing | About