Enum-like arguments in R

Question

I\'m new to R and I\'m currently trying to supply the enumeration-like argument to the R function (or the RC/R6 class method), I currently use character vector plus ma

Answer 1

I like to use environments as replacement for enums because you can lock them to prevent any changes after creation. I define my creation function like this:

Enum <- function(...) {

  ## EDIT: use solution provided in comments to capture the arguments
  values <- sapply(match.call(expand.dots = TRUE)[-1L], deparse)

  stopifnot(identical(unique(values), values))

  res <- setNames(seq_along(values), values)
  res <- as.environment(as.list(res))
  lockEnvironment(res, bindings = TRUE)
  res
}

Create a new enum like this:

FRUITS <- Enum(APPLE, BANANA, MELON)

We can the access the values:

FRUITS$APPLE

But we cannot modify them or create new ones:

FRUITS$APPLE <- 99  # gives error
FRUITS$NEW <- 88  # gives error