My hacker rank prelude for F#

hackerrankprelude.fsx

open System
open System.Collections.Generic
let rl = Console.ReadLine
let splsp (s:string) = s.Split([|' '|], StringSplitOptions.RemoveEmptyEntries)
let getTwo (a:_[]) = a.[0], a.[1]
let getThree (a:_[]) = a.[0], a.[1], a.[2]
let callN n action = seq { for i = 1 to n do yield action()} |> Seq.toArray
let iterrl f =
  let rec loop () =
    let l = rl()
    if l = null then () else f l; loop()
  loop()
[<AutoOpen>]
module DictionaryHelper =
    type Dictionary<'TK, 'TV> with
        member this.TryGetValueOpt k =
            match this.TryGetValue k with
            | true, v -> Some v
            | _ -> None
let mkHist s =
    let d = Dictionary<_, int>()
    let add x = defaultArg (d.TryGetValueOpt x) 0 |> fun c -> d.[x] <- c + 1
    Seq.iter add s
    d