getsetattr(x, which, value)

setattr(x, which, value)

setattributes(x, attributes)

x <- as.single(runif(10))
  attr(x, "Csingle")

  f <- function(x)attr(x, "Csingle") <- NULL
  g <- function(x)setattr(x, "Csingle", NULL)

  f(x)
  x
  g(x)
  x

 ## Not run: 

  # restart R
  library(bit)

  mysingle <- function(length = 0){
    ret <- double(length)
    setattr(ret, "Csingle", TRUE)
    ret
  }

  # show that mysinge gives exactly the same result as single
  identical(single(10), mysingle(10))

  # look at the speedup and memory-savings of mysingle compared to single
  system.time(mysingle(1e7))
  memory.size(max=TRUE)
  system.time(single(1e7))
  memory.size(max=TRUE)

  # look at the memory limits
  # on my win32 machine the first line fails beause of not enough RAM, the second works
  x <- single(1e8)
  x <- mysingle(1e8)

  # .g. performance with factors
  x <- rep(factor(letters), length.out=1e7)
  x[1:10]
  # look how fast one can do this
  system.time(setattr(x, "levels", rev(letters)))
  x[1:10]
  # look at the performance loss in time caused by the non-needed copying
  system.time(levels(x) <- letters)
  x[1:10]


  # restart R
  library(bit)

  simplefactor <- function(n){
    factor(rep(1:2, length.out=n))
  }

  mysimplefactor <- function(n){
    ret <- rep(1:2, length.out=n)
    setattr(ret, "levels", as.character(1:2))
    setattr(ret, "class", "factor")
    ret
  }

  identical(simplefactor(10), mysimplefactor(10))

  system.time(x <- mysimplefactor(1e7))
  memory.size(max=TRUE)
  system.time(setattr(x, "levels", c("a","b")))
  memory.size(max=TRUE)
  x[1:4]
  memory.size(max=TRUE)
  rm(x)
  gc()

  system.time(x <- simplefactor(1e7))
  memory.size(max=TRUE)
  system.time(levels(x) <- c("x","y"))
  memory.size(max=TRUE)
  x[1:4]
  memory.size(max=TRUE)
  rm(x)
  gc()


## End(Not run)