Implementation of `NonEmpty` in F# with `map`, `concat` and `bind`.

NonEmpty.fs

type 'a NonEmpty = NonEmpty of 'a * 'a list

let inline (&|) head tail = NonEmpty (head, tail)
let inline (|&|) head = NonEmpty (head, [])
let toList = function NonEmpty (head, xs) -> head :: xs

let mapNonEmpty f = function 
  NonEmpty (head, xs) -> NonEmpty (f head, List.map f xs)

let bindNonEmpty (f: 'a -> 'b NonEmpty) = function
  | NonEmpty (head, xs) ->
    match f head with
      | NonEmpty (b, bs) ->
         let bs' = xs |> List.collect (f >> toList)
         b &| (List.append bs bs')

let concatNonEmpty = function
  | NonEmpty (NonEmpty (head, rest), remaining) ->
      NonEmpty (head, List.append rest <| List.collect toList remaining)

let bindNonEmpty' (f: 'a -> 'b NonEmpty) =
  mapNonEmpty f >> concatNonEmpty

let example = 1 &| [2]

let addOne = (+) 1
let nextTwo i = i + 1 &| [i + 2]

[
  mapNonEmpty addOne
  bindNonEmpty nextTwo
  bindNonEmpty' nextTwo
]
|> List.iter (fun f -> f example |> printfn "%A")