On 09:40 Wed 05 Jun     , Ingo Karkat wrote:
> On 05-Jun-2013 09:10 +0200, Christian Brabandt wrote:
> 
> > On Wed, June 5, 2013 08:56, Ingo Karkat wrote:
> >> On 05-Jun-2013 08:03 +0200, Christian Brabandt wrote:
> >>
> >>> [...] the old engine has an long standing bug with \%V ;(
> >>>
> >>> e.g:
> >>>
> >>> vim -u NONE -N
> >>> ifoobar<esc>
> >>> 0ve<esc>
> >>> /\%Vfoobar\%V
> >>>
> >>> I should have probably provided a fix long ago.
> >>
> >> Where is the bug, that there's no match?! That's intended, as the last
> >> \%V matches zero-width _after_ the end of "foobar", but the visual
> >> selection ends on the "r". You'd have to use /\%Vfooba\%Vr here. (The
> >> example at :help \%V is wrong about this corner case, too.)
> > 
> > I am not sure, it is intended. I certainly wouldn't expect this (and
> > the doc is wrong in this regard, as you said). Since
> > \%V is zero-width, I would expect the \%V to still match the end of the
> > visual selection.
> 
> Zero-width means: Matches at the current position, but does not consume
> the character; i.e. the next match is made at the same position.
> What is needed at the final atom is: Matches at the previous position
> (that has already been consumed). I don't know how difficult that is to
> implement in the regular expression engine(s), but I think such a new
> \%<V atom would be helpful.
> 
> In my opinion it is hard to change the existing \%V in a way to fit both
> uses: It just matches anywhere inside a selection, and has no notion of
> start or end of selection. Therefore, it's presumably difficult to
> change its behavior at the end of the selection without introducing
> off-by-one errors elsewhere. I'm already struggling to come up with a
> good and precise documentation for the new behavior; the current one is
> at least simple to grasp (when you understand zero-width matches). And
> it would be a compatibility-breaking change.
> 
> >> The general case is this ugly beast: /\%Vfoobar\%(\%V\|\%(\%V.\)\@<=\).
> > 
> > Yes, very ugly and not easily understandable.
> > 
> >> Since restricting the match to inside the entire selection is such a
> >> common use case (see the related vis.vim plugin), I think it would be
> >> worthwhile to have a special atom (e.g. \%<V) that matches if the
> >> _preceding character_ is inside the selection, allowing this much nicer
> >> pattern: /\%Vfoobar\%<V
> > 
> > I can understand why this happens but nevertheless it is an annoying
> > corner-case to consider when using the \%V atom, so I'd like to have
> > this issue resolved.
> 
> Yes, at least the help should warn about this corner case. I ran into it
> (and came up with the complex correct regexp) in some of my plugins, but
> I think \%V is one of the more obscure atoms few people use. Probably
> more users rely on the vis.vim plugin, which solves the problem in a
> completely different way.
> 
> -- regards, ingo
> 
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And what about this pattern:
/\%Vfooba\%Vr

Thanks I did not know this pattern and it is very handy.  I always felt
that the search commands /, ? should have a range, so that one can limit
the search to part of a text.  What about having two commands :<range>/
and :<range>? for searches limited to the <range> of lines.

Best regards,
Marcin

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