Use base pipe in examples

[georgestagg]

Update e.g.

purrr/R/keep.R

Lines 64 to 76 in d9ae235

	#' Keep/discard elements based on their name/position
	#'
	#' @inheritParams map_at
	#' @seealso [keep()]/[discard()] to keep/discard elements by value.
	#' @export
	#' @examples
	#' x <- c(a = 1, b = 2, cat = 10, dog = 15, elephant = 5, e = 10)
	#' x %>% keep_at(letters)
	#' x %>% discard_at(letters)
	#'
	#' # Can also use a function
	#' x %>% keep_at(~ nchar(.x) == 3)
	#' x %>% discard_at(~ nchar(.x) == 3)