Are there raw strings in R for regular expressions?

Question

In Python you can use raw strings:

import re
re.sub(r"\\", ":", "back\\slash")  # r"\\" instead of "\\\\"

Does this exist in R as well? For example, here is an equivalent code snippet without raw strings in R:

library(stringr)
str_replace("back\\slash", "\\\\", ":")

I would love to be able to do this:

str_replace("back\\slash", raw("\\"), ":")

Does this functionality already exist, or should I just implement my own function raw()?

Answer 1

For your example a R < 4.0.0 alternative would be the other way round to use a function that automatically escapes special characters. Here the stringi package is helpful.

library(stringr)
library(stringi)
str_replace("back\\slash", stri_escape_unicode("\\"), ":")

Since this is very verbose defining r <- stri_escape_unicode would come close to your desired functionality (r("\\")).

The stringi package also has a function to reverse escaping stri_unescape_unicode which is useful in a shiny apps, where user inputs are automatically escaped.

Answer 2

As of R 4.0.0 this is available.

Raw character constants are also available using a syntax similar to the one used in C++: r"(...)" with ... any character sequence, except that it must not contain the closing sequence )". The delimiter pairs [] and {} [c]an also be used. For additional flexibility, a number of dashes can be placed between the opening quote and the opening delimiter, as long as the same number of dashes appear between the closing delimiter and the closing quote.

From the example in ?Quotes:

r"{(\1\2)}"
## [1] "(\\1\\2)"

(note, the double-backslashes are R's printed representation of backslashes: cat() on this object will print (\1\2))