On May 25, Jonathan Scott Duff said:
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.
But that's not even the point. The ! in <!after ...> is not what makes
<!after ...> a zero-width assertion, it's the 'after' that does that. All
the ! does is negate the boolean sense of the assertion, which seems like
a useful thing to have.
Hrm, but I think I see the problem. How does one define "negation" for an
arbitrary assertion? Is <!foo> saying "if <foo> matches, fail"? Because
then <!prop X> doesn't make mean the same as <-prop X>. We don't want
negation, we want complement.
I guess '!' is only well-defined for zero-width assertions. When you want
to say <!foo>, I guess <!before <foo>> or <!after <foo>> is the proper way
to go.
--
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
