ROP Example

gistfile1.txt

type Customer = {Name:string; Email:string}
type Input = {Customer:Customer; MaxNameLength:int}

type Result<'t> =
| Good of 't
| Bad of string

let bind switchFunction =
    fun twoTrackInput ->
        match twoTrackInput with
        | Good g -> switchFunction g
        | Bad b -> Bad b

let (>>==) twoTrackInput switchFunction =
    bind switchFunction twoTrackInput

let nameNotBlank input =
    if input.Name = "" then Bad "Need Name"
    else Good input

let nameMax maxAmount input =
    if input.Name.Length > maxAmount then Bad "Too Long"
    else Good input

let emailNotBlank input =
    if input.Email = "" then Bad "Need Email"
    else Good input

let validateRequest twoTrackInput =
    twoTrackInput
    >>== nameNotBlank
    >>== nameMax 50
    >>== emailNotBlank

let customer = {Name="Jamie";Email="jamie@aol.com"}
let customerInput = Good customer
validateRequest customerInput