Convert rex-style regexes to normal/conventional form regexes

[debajyoti7]

For eg.
Convert rex-style [[:alpha:]](?:(?:[[:digit:]]){1,2}(?:[[:alpha:]]){1,2})(?:(?:[[:digit:]]){6,7})
to conventional style [A-Za-z](?:(?:[\d]){1,2}(?:[A-Za-z]){1,2})(?:(?:[\d]){6,7})
so they can be plugged into external (non-R) models directly.

[jimhester]

The [:alpha:] is a POSIX character classes and are actually widely used outside of R. If your language does not support them there is a table in the above link that supplies conversions. You could convert the regular expressions by defining a map and a call to gsub().

convert <- function(x) {
  map <- c("\\[:alpha:\\]" = "a-zA-Z", "\\[:digit:\\]" = "0-9")
  for (i in seq_along(map)) {
    x <- gsub(names(map)[[i]], map[[i]], x)
  }
  x
}
convert("[[:alpha:]](?:(?:[[:digit:]]){1,2}(?:[[:alpha:]]){1,2})(?:(?:[[:digit:]]){6,7})")
#> [1] "[a-zA-Z](?:(?:[0-9]){1,2}(?:[a-zA-Z]){1,2})(?:(?:[0-9]){6,7})"

[debajyoti7]

@jimhester Thank you.
That's actually how I'm handling it right now and supplying the outputs to Watson Knowledge Studio. The easy check for me is to make it compliant to this web platform.
I opened the issue as suggested by @kevinushey via Twitter.

[kevinushey]

It might be worth considering allowing:

1. Different 'modes' for rex to operate in, defining how it generates regular expressions,
2. Some kind of user hook that defines what replacement is used for a particular rex construct.

... although this is unlikely to happen in the short-term.