* Re: Bug? RE: Un-patch: new pattern matching code
@ 1999-08-09 8:42 Sven Wischnowsky
1999-08-09 17:29 ` Bart Schaefer
0 siblings, 1 reply; 4+ messages in thread
From: Sven Wischnowsky @ 1999-08-09 8:42 UTC (permalink / raw)
To: zsh-workers
Andrej Borsenkow wrote:
> > Anyone who knows any computer science will probably notice that, while it's
> > pretty much a finite state machine, some states are more finite than
> > others. In particularly, backtracking on excluded matches, where in
> > (foo~bar)rod the `bar' only has to match the `foo' and the `rod' is
> > irrelevant, need some extra state recording, and I have retained the old
> > trick that eliminates infinite loops and prevents exponential behaviour
> > when failing to match against things like `(f#o#)#' (the version of perl
> > here goes into an infinite loop when given `(f*o*)*', so it isn't trivial).
> > This has meant leaving holes for pointers in the compiled expression, which
> > ought to work (I've tried to make sure everything is aligned to pointer
> > size anyway) but is probably the most dubious part of the proceedings.
> >
>
> bor@itsrm2:~%> foo=ab12xy
> bor@itsrm2:~%> print ${foo/[[:digit:]]#}
> abxy
> bor@itsrm2:~%> print ${(S)foo/[[:digit:]]#}
> ab12xy
> bor@itsrm2:~%> print ${foo//[[:digit:]]#}
> abxy
> bor@itsrm2:~%> print ${(S)foo//[[:digit:]]#}
> here zsh hangs completely.
It was repeatedly matching the empty string, of course. This makes
that be handled as a special case, stepping one character forward even
if zero characters were matched.
Maybe Peter will have to decide if this is the right thing to do here.
Bye
Sven
P.S.: At least simple things like ${a#*/}, ${a%/*}, ${a##*/}, and
${a%%/*} seem to be circa three times slower than before for me.
--- os/glob.c Mon Aug 9 10:40:41 1999
+++ Src/glob.c Mon Aug 9 10:33:49 1999
@@ -1971,8 +1971,11 @@
*ptr = sav;
}
}
- if (!--n || (n <= 0 && (fl & SUB_GLOBAL)))
+ if (!--n || (n <= 0 && (fl & SUB_GLOBAL))) {
*sp = get_match_ret(*sp, t-s, mpos-s, fl, replstr);
+ if (mpos == start)
+ mpos++;
+ }
if (!(fl & SUB_GLOBAL)) {
if (n) {
/*
--
Sven Wischnowsky wischnow@informatik.hu-berlin.de
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Bug? RE: Un-patch: new pattern matching code
1999-08-09 8:42 Bug? RE: Un-patch: new pattern matching code Sven Wischnowsky
@ 1999-08-09 17:29 ` Bart Schaefer
0 siblings, 0 replies; 4+ messages in thread
From: Bart Schaefer @ 1999-08-09 17:29 UTC (permalink / raw)
To: zsh-workers
On Aug 9, 10:42am, Sven Wischnowsky wrote:
} Subject: Re: Bug? RE: Un-patch: new pattern matching code
}
} P.S.: At least simple things like ${a#*/}, ${a%/*}, ${a##*/}, and
} ${a%%/*} seem to be circa three times slower than before for me.
(I saw the followup about -O2 eliminating this.) It does appear that a
shell compiled for debugging starts up noticably slower with the new
code (and using my init files). I use a LOT of "case ... exac" tests in
my init files with fairly simple patterns in the labels (often with no
wildcards, occasionally with only (|) alternation).
--
Bart Schaefer Brass Lantern Enterprises
http://www.well.com/user/barts http://www.brasslantern.com
^ permalink raw reply [flat|nested] 4+ messages in thread
* Re: Bug? RE: Un-patch: new pattern matching code
@ 1999-08-09 11:33 Sven Wischnowsky
0 siblings, 0 replies; 4+ messages in thread
From: Sven Wischnowsky @ 1999-08-09 11:33 UTC (permalink / raw)
To: zsh-workers
I wrote:
> P.S.: At least simple things like ${a#*/}, ${a%/*}, ${a##*/}, and
> ${a%%/*} seem to be circa three times slower than before for me.
Sorry for the false alarm. With -O2 they have approximately the same
speed.
Bye
Sven
--
Sven Wischnowsky wischnow@informatik.hu-berlin.de
^ permalink raw reply [flat|nested] 4+ messages in thread
* Bug? RE: Un-patch: new pattern matching code
1999-08-06 15:47 Peter Stephenson
@ 1999-08-09 8:10 ` Andrej Borsenkow
0 siblings, 0 replies; 4+ messages in thread
From: Andrej Borsenkow @ 1999-08-09 8:10 UTC (permalink / raw)
To: Peter Stephenson, Zsh hackers list
> Anyone who knows any computer science will probably notice that, while it's
> pretty much a finite state machine, some states are more finite than
> others. In particularly, backtracking on excluded matches, where in
> (foo~bar)rod the `bar' only has to match the `foo' and the `rod' is
> irrelevant, need some extra state recording, and I have retained the old
> trick that eliminates infinite loops and prevents exponential behaviour
> when failing to match against things like `(f#o#)#' (the version of perl
> here goes into an infinite loop when given `(f*o*)*', so it isn't trivial).
> This has meant leaving holes for pointers in the compiled expression, which
> ought to work (I've tried to make sure everything is aligned to pointer
> size anyway) but is probably the most dubious part of the proceedings.
>
bor@itsrm2:~%> foo=ab12xy
bor@itsrm2:~%> print ${foo/[[:digit:]]#}
abxy
bor@itsrm2:~%> print ${(S)foo/[[:digit:]]#}
ab12xy
bor@itsrm2:~%> print ${foo//[[:digit:]]#}
abxy
bor@itsrm2:~%> print ${(S)foo//[[:digit:]]#}
here zsh hangs completely.
^ permalink raw reply [flat|nested] 4+ messages in thread
end of thread, other threads:[~1999-08-09 17:29 UTC | newest]
Thread overview: 4+ messages (download: mbox.gz / follow: Atom feed)
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1999-08-09 8:42 Bug? RE: Un-patch: new pattern matching code Sven Wischnowsky
1999-08-09 17:29 ` Bart Schaefer
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1999-08-09 11:33 Sven Wischnowsky
1999-08-06 15:47 Peter Stephenson
1999-08-09 8:10 ` Bug? " Andrej Borsenkow
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