Non-reference class in R with class methods

Class6.R

Class6 <- function(...) {
  structure(list(...), class = "Class6")
}
 
# Methods for the class
Class6_methods <- list(
  sum_xy = function(self) {
    self$x + self$y
  },
  inc_x = function(self, amount = 1) {
    self$x <- self$x + amount
    self
  }
)
 
# Redefine $ so that you can use it to invoke class methods
`$.Class6` <- function(x, name) {
  # This is a little crude, but it works
  if (name %in% names(x)) {
    res <- .subset2(x, name)
    if (is.function(res)) {
      # If it's a function, curry it
      function(...) res(x, ...)
    } else {
      res
    }
  } else if (name %in% names(Class6_methods)) {
    # Return a curried function
    fun <- Class6_methods[[name]]
    function(...) fun(x, ...)
  } else {
    stop('Member and method with name ', name, ' not found.')
  }
}
`[[.Class6` <- `$.Class6`
 
# Create a new object z, which also has an individual method
z <- Class6(
  x=1,
  y=2,
  prod_xy = function(self) self$x * self$y
)
z
z$x
z$sum_xy()
z$inc_x
z$inc_x()$inc_x(4)
z$sum_xy()
z <- z$inc_x()$inc_x(4)
z$sum_xy()
z$prod_xy()