[R] Question about PERL lookahead construct in regex's

[Bert Gunter]

Thank you.
That indeed dispels my brain fog!

Best,
Bert


Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )


On Wed, Aug 12, 2020 at 6:35 AM Stefan Evert <stefanML using collocations.de>
wrote:

>
> > On 10 Aug 2020, at 18:36, Bert Gunter <bgunter.4567 using gmail.com> wrote:
> >
> > But this appears to be imprecise (it confused me, anyway). The usual
> sense
> > of "matching" in regex's is "match the pattern somewhere in the string
> > going forward." But in the perl lookahead construct it apparently must
> > **exactly** match *everything* in the string that follows.
> >
> > Questions:
> > Am I correct about this? If not, what do I misunderstand?
>
> I think you're confused about the terminology.  To _match_ a regular
> expression is to find a substring described by the regexp at a given
> starting point; what you have in mind is to _search_ a string for matches
> of a regular expression.
>
> Python uses this terminology in its regexp matching functions, and from
> what you cited in the documentation so do Perl and PCRE in their docs.
>
> Best,
> Stefan
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