ce.fs

module James

open System

let strToInt str =
  try
    Some (Int32.Parse(str))
  with
    | _ -> None

type OptionBuilder () = 
  member this.Return x = Some(x)
  member this.Bind(e, f) = match e with
    | Some(x) -> f x
    | None    -> None


let myWorkflow = new OptionBuilder()

let stringAddition x y z =
  myWorkflow
    {
      let! a = strToInt x
      let! b = strToInt y
      let! c = strToInt z
      return a + b + c
    }

stringAddition "3" "2" "1"
stringAddition "99" "abc" "1"

let strAdd str i =
  match strToInt str with
    | Some(x) -> Some(i + x)
    | None    -> None

let (>>=) m f = Option.bind f m

let y = strToInt "1" >>= strAdd "100" >>= strAdd "33"

let y = strToInt "1" >>= strAdd "n00" >>= strAdd "33"