Ingo Karkat wrote:
> Hello Vim developers,
>
> there's yet another discrepancy between the regular expression engines:
>
> for n in [1,2] | echo match('",abc" in "abc,abc"', '\%#=' . n .
> '\1\@<=,\([a-z]\+\)') | endfor
>
> I actually found this while checking out an example from the help
> (trying to understand why a regexp I use in a plugin didn't work):
>
> ,----[ :help /\@<= ]----
> | The part of the pattern after "\@<=" and "\@<!" are checked for a
> | match first, thus things like "\1" don't work to reference \(\) inside
> | the preceding atom. It does work the other way around:
> | Example matches ~
> | \1\@<=,\([a-z]\+\) ",abc" in "abc,abc"
> `----
>
> The NFA engine somehow doesn't properly handle the backreference
> assertion and finds a match where it shouldn't.
>
> To reproduce, use above scriptlet or the identical attached script:
>
> vim -N -u NONE -S bad-re5.vim
> 14
> 1
>
> This is with a huge build of Vim 7.4.383, running in an Ubuntu 13.10 x64
> VM.
Thanks, I'll add it to the todo list.
Keep in mind that NFA does not actually support backreferences, that it
works at all in Vim is a bit of a miracle :-).
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