R/autofun.R

In samuel-rosa/autofun: Automatic Generation of R Functions

#' Automatic Generation of R Functions
#' 
#' Automatically generate an R funtion using source code contained in an R 
#' script.
#' 
#' @param fun.name Name of the function.
#' 
#' @param read.file A connection, or a character string naming the file that
#' contains the R source code that will constitute the body of the
#' function.
#' 
#' @param write.file A connection, or a character string naming the file to 
#' write the function to.
#' 
#' @details
#' The idea behind \code{autofun} is to use a standalone R script to create an
#' R function. This is done parsing the R script and using the returned 
#' expression as the function body.
#' 
#' A function \code{foo} returned by \code{autofun} gets all the arguments from 
#' the working environment. This is done by evaluating the function with 
#' \code{eval(foo())}. Such a function can return several objects.
#' 
#' @author
#' Alessandro Samuel-Rosa \email{alessandrosamuelrosa@@gmail.com}
#' 
#' @seealso \code{\link{base}{parse}}, \code{\link{utils}{capture.output}},
#' \code{\link{base}{eval}}, \code{\link{base}{expression}}
#' 
#' @export
autofun <- 
  function (fun.name, read.file, write.file) {
    
    # Prepare info
    info <- .autofun_info(read.file)

    # Function head, body and tail
    head <- paste(fun.name, "<-function(...){", sep = "")
    body <- capture.output(parse(file = read.file))
    tail <- paste("}")
    
    # Prepare output and write to file
    text <- c(info, head, body, tail, sep = "")
    writeLines(text = text, con = write.file)
  }

# INTERNAL FUNCTION - prepare comments added to the generated R file ###########
.autofun_info <-
  function (read.file) {
    pv <- packageVersion("autofun")
    info <- paste("# Generated by autofun (", pv, "): do not edit by hand!!!\n", 
                  "# Please edit source code in ", read.file, sep = "")
    return (info)
  }