R/peek_back-set.rdeque.R

In rstackdeque: Persistent Fast Amortized Stack and Queue Data Structures

#' @export
#' @title Assign to/modify the back of an rdeque
#' 
#' @description Allows modification access to the back of a deque.
#' 
#' @details Runs in \eqn{O(1)} worst case time. Throws an error if the deque is empty.
#' @param d rdeque to modify the back element of.
#' @param value value to assign to the back data element.
#' @param ... additional arguments to be passed to or from methods.
#' @return modified rdeque.
#' @seealso \code{\link{peek_back.rdeque}} for accessing the back element.
#' @examples
#' d <- rdeque()
#' d <- insert_front(d, data.frame(a = 1, b = 1))
#' d <- insert_front(d, data.frame(a = 1, b = 1))
#' 
#' peek_back(d)$a <- 100
#' print(d)
#' 
#' peek_back(d) <- data.frame(a = 100, b = 100)
`peek_back<-.rdeque` <- function(d, ..., value) {
  if(length(d) < 1) {
    stop("cannot assign to the back of an empty deque, try checking with empty() first")
  }
  d$r$head$data <- value
  return(d)
}