||++ for R

iipp.R

# return a if a is defined and not null, otherwise return b
`%|%` <- function(a, b){
  try({
    if(!is.null(eval(substitute(a))))
      return(a)
    }, silent=TRUE);
  b
}

# assign b to a if a is undefined or null, compare to ruby's ||=
`%<|-%` <- function(a, b){
  # This should generate a <- a %|% b, see http://rpubs.com/hadley/do-call2
  # Use `<-` instead of assign to allow  things like df$a %<|-% 2
  do.call(`<-`,
    list(substitute(a), substitute(a %|% b)),
    envir=parent.frame())
}