regex - Why and when to use optional perl parameters in R -


out of curiosity, have general question optional perl parameter in r funtions grep. title says in title, i'd know why , when 1 should use option. general thing if possible?

in addition thought reason of such parameter. must have decided way go , wonder why.

i positive of knows answer.

regular expressions come in multiple flavors. different flavors have different features, supported syntax, or other obscure differences.

perl considered 1 of feature-complete flavor, led develomment of pcre (perl-compatible regular expressions) library, allows use of perl flavor in other languages. there other regex libraries support perl syntax extent.

contrast default regex flavor used in r: posix ere, 1 of least feature-complete.

you can use this site compare flavors.


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