why I can match "\v" with regex "\v","\\v"and"\\\v”

[sandorDao]

I can't figure out why all of these work the same.

str_extract("\vb", "\v")

str_extract("\vb", "\\v")

str_extract("\vb", "\\\v")

[EliMiller]

Hello sandorDao,
Welcome to the community!
This seems to be a quirk in how R's ICU regex engine is parsing escape characters. Here is some more info on escaping using stringr. In the first case, \v is referring to a vertical tab character. In the second, \\v, the two backslashes are escaped into one so it's looking for \ and a v. The link above will help with the last case. It looks like a sort of recursive escaping is happening in this case.

Hope this helps!