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c-cube/perms.ml

Last active August 3, 2016 14:18
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permutations using Sequence
Raw
perms.ml
#require "sequence";;
open Sequence.Infix;;
let rec perms = function
| [] -> Sequence.return []
| x :: tail -> perms tail >>= insert x
and insert x l = match l with
| [] -> Sequence.return [x]
| y :: tail ->
Sequence.cons (x :: l) (insert x tail >|= fun tail' -> y :: tail')
;;
perms [1;2;3;4] |> Sequence.to_list;;
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