some very minimal examples of object oriented programming with R

s3example.R

myfun <- function(){
  out <- list()
  out$x <- LETTERS
  out$y <- "hello world"
  class(out) <- "vtable"
  out
} 
print.vtable <- function(x){
  cat("object of class vtable")
  print(str(x$x))
}
"[.vtable" <- function(x, i){
  x$x[i]
}
"$.vtable" <- function(x, i){
  print("used $ operator")
  x
}
z <- myfun()
print(z)
z[6]
z$y

s4example.R

setClass("vtable",  representation(x = "character", y="character"))
x <- new("vtable", x=as.character(1:10), y = "heel")
setMethod("show", "vtable", function(object){
  print("hello")
  print(object@x)
})
x