R: Push, Pop, Shift, Unshift

push-pop-shift-unshift.R

# Inspired:
# https://gist.github.com/leeper/d6d085ac86d1e006167e
# http://www.johnmyleswhite.com/notebook/2009/12/07/implementing-push-and-pop-in-r/

push <- function(x, values) {
  assign(as.character(substitute(x)), c(x, values), parent.frame())
  invisible()}

pop <- function(x) {
  if(length(x) == 0) {return(NA)}
  popret <- x[length(x)]
  assign(as.character(substitute(x)), x[-length(x)], parent.frame())
  return(popret)}

unshift <- function(x, values) {
  assign(as.character(substitute(x)), c(values, x), parent.frame())
  invisible()}

shift <- function(x) {
  if(length(x) == 0) {return(NA)}
  shiftret <- x[1]
  assign(as.character(substitute(x)), x[2:(length(x))], parent.frame())
  return(shiftret)}

# z <- letters[1:11]
# z
# 
# pop(z)
# z
# push(z, "v")
# z
# shift(z)
# z
# unshift(z, c("m", "n"))
# z