[R] gsub regexp question

[Jeff Newmiller]

I believe the backslash is not considered an escape character by the extended RE library used by R (perl=FALSE), so it is being treated as a literal. This means that the last ] is outside the character class and is the atom that the * applies to.

 gsub("^([[:alnum:]\\[\\]]*).*", "\\1", "a]]]rray[n] <- 10", perl=FALSE)

yields

"a]]]"

(Using F in place of FALSE is bad form.)
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Sent from my phone. Please excuse my brevity.

On October 15, 2014 4:42:00 AM PDT, ALBERTO VIEIRA FERREIRA MONTEIRO <albmont at centroin.com.br> wrote:
>I just found a curious behaviour of regexp and I'd like to share with
>y'all.
>
>gsub("^([[:alnum:]\\[\\]]*).*", "\\1", "array[n] <- 10", perl=T) #
>works as expected ("array[n]")
>
>gsub("^([[:alnum:]\\[\\]]*).*", "\\1", "array[n] <- 10", perl=F) #
>doesn't work ("a")
>
>I didn't find anything in the documentation explain what's going on,
>and why the second gsub doesn't work.
>
>Alberto Monteiro
>
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