[null_driver]

Ocaml also has `@@` which gives `'a -> ('a -> 'b) -> 'b = <fun>` and `|>` for `('a -> 'b) -> 'a -> 'b = <fun>` so you can also do:

```ocaml

  type point = { x: float; y: float};;

  let euclidean a a' =
    let xd = (a'.x -. a.x) in
    let yd = (a'.y -. a.y) in
    sqrt ((xd*.xd) +. (yd*.yd))
  ;;

  let is_in_unit_circle x =
    x <= 1.

  let quadsolve iterations hits =
    ((4. *. hits) /. Float.of_int iterations)

  let estimate iters =
    let origin    = { x = 0.; y = 0. } in
     Array.init iters (fun _ -> { x = (Random.float 1.); y = (Random.float 1.) })
     |> Array.map (euclidean origin)
     |> Array.map is_in_unit_circle
     |> Array.fold_left (fun x y ->  if y then x +. 1. else x ) 0.
     |> quadsolve iters

;;

```

  utop # estimate 1000000;;
  - : float = 3.141432

Edit: formatting

[unsafecast]

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