local({
  previous_options <- options(warn = 2, digits = 8, stringsAsFactors = FALSE)
  on.exit(options(previous_options), add = TRUE)
  visits <- c(8, 12, 10)
  cat("doubled:", paste(visits * 2, collapse = ", "), "\n")
  cat("sequence:", paste(seq(2, 8, by = 2), collapse = ", "), "\n")
  cat("empty length:", length(numeric(0)), "\n")
  invisible(NULL)
})