F# Computation Expressions

maybe.fs

open System

let divideBy bottom top =
    if bottom = 0
    then None
    else Some(top/bottom)

type MaybeBuilder() =

    member this.Bind(x, f) = 
        printfn "x: %A, f: %A" x f
        match x with
        | None -> None
        | Some a -> f a

    member this.Return(x) = 
        Some x
   
let maybe = new MaybeBuilder()

let divideByWorkflow init x y z = 
    printfn "x %A" x
    maybe 
        {
        let! a = init |> divideBy x
        let! b = a |> divideBy y
        let! c = b |> divideBy z
        return c
        }  
        
let good = divideByWorkflow 12 3 2 1

let pipeInto (someExpression,lambda) =
   match someExpression with
   | None -> 
       None
   | Some x -> 
       x |> lambda 

let return' c = Some c

let divideByWorkflowPiped x y w z = 
    pipeInto (x |> divideBy y, fun a ->
    pipeInto (a |> divideBy w, fun b ->
    pipeInto (b |> divideBy z, fun c ->
    return' c 
    )))
    
let goodPipe = divideByWorkflowPiped 12 3 2 1