# A little function that just concatenates paths (as strings) 
# to produce a "path" to some file/directory
path_c <- function(path1,  ...,  sep) {
    if (missing(sep)) {
        # Note that the directory separator depends on the OS
        # (e.g. sep = "\\" on Windows)
        sep <- switch(.Platform$OS.type,
                      unix = "/",
                      windows = "\\"
        )
    }
    paste(path1, ..., sep = sep)
}

#
# This one is only useful from within RStudio
# 
editcode <- function(filename, dir, ...){
    if (missing(dir)) dir <- getwd()
    file <- path_c(dir, filename, ...)
    if (file.exists(file)) {
        file.edit(file)
    } else {
        file.choose()
    }
}

#
#  Check that a variable is defined 
#  (from stackoverflow 
#  https://stackoverflow.com/questions/9368900/how-to-check-if-object-variable-is-defined-in-r
#  )
#  
is.defined <- function(sym) {
    sym <- deparse(substitute(sym))
    env <- parent.frame()
    exists(sym, env)
}