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

Stefan Evert @te|@nML @end|ng |rom co||oc@t|on@@de
Wed Aug 12 15:35:20 CEST 2020


> 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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