random2.ml

(* From Elm 0.19 *)
let rec get_by_weight : float * 'a -> (float * 'a) list -> float -> 'a =
	fun (weight, value) others countdown ->
    match others with
      | [] ->
          value

      | second :: other_others ->
          if countdown <= abs_float weight then
            value
          else
            get_by_weight second other_others (countdown -. abs_float weight)

(* From Elm 0.19 *)
let weighted : float * 'a -> (float * 'a) list -> 'a =
  fun first others ->
    let normalize (weight, _) =
      abs_float weight
    in
    let total =
      normalize first +. List2.fsum (List.map normalize others)
    in
    get_by_weight
      first
      others
      (Random.float total)

let rec sample_unique_helper :
 'a list -> (int * (unit -> 'a)) list -> 'a list =
  fun acc info ->
    match info with
      | [] ->
          acc

      | (size, gen) :: rest_info ->
          if List.length acc >= size then
            sample_unique_helper acc rest_info
          else
            let x =
              gen ()
            in
            if Option.is_some (List.find_opt ((=) x) acc) then
              sample_unique_helper acc info
            else
              sample_unique_helper (x :: acc) info

let sample_unique : (int * (unit -> 'a)) list -> 'a list =
  fun info ->
    sample_unique_helper [] info
      |> List.rev