Q: Why isn't \\b in gsubfn in R working for me? I have a string like this:
vect <- c("Thin lines are not great, I am in !!! AND You shouldn't be late OR you loose")

I want to replace, "in" to %in%", "AND" to "&", "OR" to "|".
I know this can be done using gsub like below:
gsub("\\bin\\b","%in%", vect),

but I need three different lines for each of the replacement, hence I choose to use gsubfn.
so I tried,
gsubfn("\\bin\\b|\\bAND\\b|\\bOR\\b", list("in"="%in%", "AND"= "&", "OR"="|"), vect)

but It returns a string with nothing changed, for some reason \\b is not working for the string. However, \\b does work great with gsub and I am able to replace all the three strings in by piping together using gsub.
My question is, why \\b is not working inside gsubfn. what I am missing inside my regex?
Please help.
Output should be:
"Thin lines are not great, I am %in% !!! & You shouldn't be late | you loose"

This works:
gsubfn("\\w+", list("in"="%in%", "AND"= "&", "OR"="|"), vect)


A: By default, Tcl regex engine is used, see gsubfn docs:

If the R installation has tcltk capability then the
  tcl engine is used unless FUN is a proto object or perl=TRUE in which case the "R" engine is used (regardless of the setting of this argument).

So, word boundaries are defined with \y:
> gsubfn("\\y(in|AND|OR)\\y", list("in"="%in%", "AND"= "&", "OR"="|"), vect)
[1] "Thin lines are not great, I am %in% !!! & You shouldn't be late | you loose"

Ainother way is by using \m as leading word boundary and \M for a trailing word boundary:
> gsubfn("\\m(in|AND|OR)\\M", list("in"="%in%", "AND"= "&", "OR"="|"), vect)
[1] "Thin lines are not great, I am %in% !!! & You shouldn't be late | you loose"

You may pass perl=TRUE and use \b:
> gsubfn("\\b(in|AND|OR)\\b", list("in"="%in%", "AND"= "&", "OR"="|"), vect, perl=TRUE)
[1] "Thin lines are not great, I am %in% !!! & You shouldn't be late | you loose"


A: Add perl = T that should do it.
gsubfn("\\bin\\b|\\bAND\\b|\\bOR\\b", list("in"="%in%", "AND"= "&", "OR"="|"), vect, perl =T)

Output
[1] "Thin lines are not great, I am %in% !!! & You shouldn't be late | you loose"


From gsub documentation

The POSIX 1003.2 mode of gsub and gregexpr does not work correctly with repeated word-boundaries (e.g., pattern = "\b"). Use perl = TRUE for such matches (but that may not work as expected with non-ASCII inputs, as the meaning of 'word' is system-dependent).

And gsubfn documentation

...   Other gsub arguments.

Doesn't explain why gsub works fine without the perl argument, but to do gsubfn it needs the perl=T
