Using delayedAssign() to use base R equivalents in new versions

Are you aware of this one? Seems to overlap somewhat:
http://cloud.r-project.org/package=stringb

stringb: Convenient Base R String Handling

Base R already ships with string handling capabilities 'out- of-the-box' but lacks streamlined function names and workflow. The 'stringi' ('stringr') package on the other hand has well named functions, extensive Unicode support and allows for a streamlined workflow. On the other hand it adds dependencies and regular expression interpretation between base R functions and 'stringi' functions might differ. This packages aims at providing a solution to the use case of unwanted dependencies on the one hand but the need for streamlined text processing on the other. The packages' functions are solely based on wrapping base R functions into 'stringr'/'stringi' like function names. Along the way it adds one or two extra functions and last but not least provides all functions as generics, therefore allowing for adding methods for other text structures besides plain character vectors.

It would be great to have equivalents for the following stringr functions:

• str_to_upper(string, locale = "en")
• str_to_lower(string, locale = "en")
• str_to_title(string, locale = "en")
• str_to_sentence(string, locale = "en")

For the first two, there are base alternatives (tolower(x) & toupper(x)), but AFAIK nothing direct for the last two.

Something like

str_replace <- function(x, pattern, replace, ...) {
  loc <- gregexpr(pattern, x, perl = TRUE)

  out <- lapply(seq_along(out), function(i) {
    match <- regmatches(x[[i]], loc[[i]])
    transform(match, ...)
  })

  regmatches(x, loc) <- out
  x
}