RE: :, ::, :::, and :::: in P6REs
> > Is that the "soon to be released" E5? > > No, that's the "to be released today" E5. > > ;-) Yy!!
Re: :, ::, :::, and :::: in P6REs
[EMAIL PROTECTED] (Paul Marquess) writes: > Is that the "soon to be released" E5? Sometime today, all being well. -- I often think I'd get better throughput yelling at the modem.
Re: :, ::, :::, and :::: in P6REs
Paul Marquess wrote: > Is that the "soon to be released" E5? No, that's the "to be released today" E5. ;-) Damian
Re: :, ::, :::, and :::: in P6REs
Simon Cozens wrote:
> While I'm messing about with REs, is it specified how :any and hypotheticals
> interoperate?
>
>"ab" =~ rx:any / $match := (\w) /;
>print $match;
>
> Can that be undefined behaviour? Please? :)
I don't think so.
It would probably result in $0 containing an array of match objects,
one for each possible match. Each of those second tier match
objects would then have a 'match' key in its hash attribute.
Hence, to see the individual hypotheticals one might write:
for @$0 -> $possible_match {
print $possible_match{match}, "\n";
}
A more intriguing possibility is that the top-level match object ($0 itself)
would *also* have a 'match' key...whose value contained a superposition of all
the possible hypotheticals. So you could also just write:
print egs( $0{match} _ "\n" );
Bwah-ha-ha-ha-hah!!
Damian
RE: :, ::, :::, and :::: in P6REs
> The behaviour is explained quite well in E5 I think. Is that the "soon to be released" E5? Paul
Re: :, ::, :::, and :::: in P6REs
[EMAIL PROTECTED] (Damian Conway) writes: > It's not an exception, but you could certainly *implement* it that way. I would argue that it is in some sense, if not an Official Perl 6 Exception, since it jumps out of several levels of a match. But yeah, I'm probably just looking at this from an implementor's viewpoint. > It gives up tracktracking the immediately preceding atom. > The behaviour is explained quite well in E5 I think. Aha! Got it, thank you. While I'm messing about with REs, is it specified how :any and hypotheticals interoperate? "ab" =~ rx:any / $match := (\w) /; print $match; Can that be undefined behaviour? Please? :) -- DEC diagnostics would run on a dead whale. -- Mel Ferentz
Re: :, ::, :::, and :::: in P6REs
> I think I can distinguish :: from ::: - :: fails the current branch point, > whereas ::: fails the entire rule. Correct. > I think I can distinguish between ::: and ; the implementation > is a bit tricky, because ::: fails the current match - easy enough - > whereas has to specify to all upper-level matches that they > failed too. Is it reasonable for failing a to be an exception? It's not an exception, but you could certainly *implement* it that way. > I don't think I can distinguish between : and ::. Essentially, how many > nodes does each commit to? I would expect the following > > [ a+ : b | c+ : d | e+ : f ] > > to do precisely the same as > > [ a+ :: b | c+ :: d | e+ :: f ] It doesn't. The first says: [ # Non-capturingly... a+#Match 1+ a's : #And never backtrack to match fewer a's b #Then match a b | # Or if that failed... c+#Match 1+ c's : #And never backtrack to match fewer c's d #Then match a d | # Or if that failed... e+#Match 1+ e's : #And never backtrack to match fewer e's f #Then match an ] whereas the second says: [ # Non-capturingly... a+#Match 1+ a's ::#And if you ever have to backtrack, # then immediately fail the entire surrounding group b #Then match a b | # Or if that failed... c+#Match 1+ c's ::#And if you ever have to backtrack, # then immediately fail the entire surrounding group d #Then match a d | # Or if that failed... e+#Match 1+ e's ::#And if you ever have to backtrack, # then immediately fail the entire surrounding group f #Then match an f ] So a single colon has the same effect as the Perl 5 (?>...) metasyntax. > I don't see why Larry describes one as "if-then", but not the other. > Basically, I don't think I'm sure what : "gives up". It gives up tracktracking the immediately preceding atom. The behaviour is explained quite well in E5 I think. Damian
:, ::, :::, and :::: in P6REs
I don't usually have problems with commitment... I think I can distinguish :: from ::: - :: fails the current branch point, whereas ::: fails the entire rule. I can do ::: trivially. I think I can distinguish between ::: and ; the implementation is a bit tricky, because ::: fails the current match - easy enough - whereas has to specify to all upper-level matches that they failed too. Is it reasonable for failing a to be an exception? This would save passing "hard" and "soft" failure codes around. is just with a couple of knobs on. I don't think I can distinguish between : and ::. Essentially, how many nodes does each commit to? I would expect the following [ a+ : b | c+ : d | e+ : f ] to do precisely the same as [ a+ :: b | c+ :: d | e+ :: f ] I don't see why Larry describes one as "if-then", but not the other. Basically, I don't think I'm sure what : "gives up". (Apologies if this doesn't sound as lucid as normal, it's 5:31am and I have been hacking too long.) -- Um. There is no David conspiracy. Definitely not. No Kate conspiracy either. No. No, there is definitely not any sort of David conspiracy, and we are definitely *not* in league with the Kate conspiracy. Who doesn't exist. And nor does the David conspiracy. No. No conspiracies here. - Thorfinn, ASR
