Convert function into string

You can turn any function into a line-by-line character vector with deparse().

deparse(setNames)
# [1] "function (object = nm, nm) "
# [2] "{"                          
# [3] "    names(object) <- nm"    
# [4] "    object"                 
# [5] "}"  

As of R 4.0, there is also deparse1(). This will return the function as a single string.

f <- function(x) {
  x + 2
}

strf <- deparse1(f)

strf
#> [1] "function (x)  {     x + 2 }"

To get the function string back to a real function, use eval() with str2lang():

f2 <- eval(str2lang(strf))

f2(4)

#> 6