R/faro.R

In RobinHankin/permutations: The Symmetric Group: Permutations of a Finite Set

`faro` <- function(n, out = TRUE) {
  if (out) {
    return(faro_gen(n, 2, p2 = cyc_len(2)))
  } else {
    return(faro_gen(n, 2))
  }
}

`faro_gen` <- function(n, m, p1 = id, p2 = id, interleave = TRUE) { # generalized Faro shuffle
  M <- matrix(seq_len(n * m), n, m)
  p1 <- as.word(p1)
  p2 <- as.word(p2)
  size(p1) <- n
  size(p2) <- m
  M <- M[as.function(p1)(seq_len(n)), as.function(p2)(seq_len(m))]
  if (interleave) {
    M <- t(M)
  }
  as.word(c(M))
}