Regex with non-capturing group using stringr in R -

i trying use non-capturing groups str_extract function stringr package. here example:

library(stringr) txt <- "foo" str_extract(txt,"(?:f)(o+)") 

this returns

"foo" 

while expect return only

"oo" 

like in post: https://stackoverflow.com/a/14244553/3750030

how use non-capturing groups in r remove content of groups returned value while using matching?

when using regex (?:f)(o+) won't capture match sure.

what capturing means storing in memory back-referencing, can used repeated match in same string or replacing captured string.

like in post: https://stackoverflow.com/a/14244553/3750030

you misunderstood answer. non-capturing groups doesn't means non-matching. it's captured in $1 ( group 1 ) because there no group prior it.

if wish only match suppose b followed a should use positive lookbehind this.

regex: (?<=f)(o+)

explanation:

• (?<=f) f present behind following token won't match.

• (o+) match , capture group (here in $1)if previous condition true.

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