Pretty printing R function

Question

I am working on some text with embedded R code. I am using Sweave to produce PDF documents. I'd like to print the functions as written into my PDF, but print(f) where f is an arbitrary function eliminates some of the key aspects, like the function name. For instance:

f <- function(x, y = 2) {
  return(x^y)
}

print(f)

yields this:

> source('~/.active-rstudio-document')
function(x, y = 2) {
  return(x^y)
}

Is there some version of print or some similar function that would print something I can cut and paste directly back into R, preserving the function declaration (the f <- part)? Also, and this is kind of an after thought, is there a way to set the maximum width in characters?

Answer 1

There's probably a better way but something like this would work:

f <- function(x, y = 2) {
  return(x^y)
}

pretty <- function(fun){
    captured <- capture.output(fun)
    captured[1] <- paste(as.character(substitute(fun)), "<-", captured[1])

    cat(paste(captured, collapse="\n"))
}

pretty(f)

## f <- function(x, y = 2) {
##   return(x^y)
## }