#' First
#'
#' @param x a sequential collection
#'
#' @return first element
#' @export
First <- function(x)
x[[1]]
#' Rest
#'
#' @param x a sequential collection
#'
#' @return collection with first element removed
#' @export
Rest <- function(x)
x[-1]
#' Last
#'
#' @param x a sequential collection
#'
#' @return last element
#' @export
Last <- function(x)
x[[length(x)]]
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