pfds 2.1 suffixes sml

2.1.suffixes.sml

(* use "suffix.sml"; *)

(* input   = output *)
(* [1,2,3] = [[1,2,3], [2,3], [3], []] *)


(* std recursion *)

fun suffixes ([]) = [[]]
  | suffixes (xs) = xs :: suffixes (tl xs);


(* iterative / tail-recursive version *)

local
  fun helper ([], rs) = rs
    | helper (xs, rs) = helper (tl xs, rs @ [xs])
in
  fun isuffixes (xs) = helper (xs, []) @ [[]]
end;