Alternate version of Private DU constructor

A different way of expressing private DU constructors.

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module Email =
    type EmailAddress =
        private
        | ValidEmail of string
        | InvalidEmail of string
    
    let ofString = function
        | "validEmail" -> ValidEmail "validEmail"
        | invalid -> InvalidEmail invalid 
    
    let (|ValidEmail|InvalidEmail|) = function
        | ValidEmail email -> ValidEmail email
        | InvalidEmail email -> InvalidEmail email

open Email

let invalid = Email.ofString "invalid"
let valid = Email.ofString "validEmail"

match invalid with
| InvalidEmail invalid -> printfn "invalid was InvalidEmail %s" invalid
| ValidEmail valid -> printfn "invalid was ValidEmail %s" valid

match valid with
| InvalidEmail invalid -> printfn "valid was InvalidEmail %s" invalid
| ValidEmail valid -> printfn "valid was ValidEmail %s" valid

type EmailAddress =
private | ValidEmail of string
| InvalidEmail of string

Full name: Script.Email.EmailAddress

union case EmailAddress.ValidEmail: string -> EmailAddress

Multiple items
val string : value:'T -> string

Full name: Microsoft.FSharp.Core.Operators.string

--------------------
type string = System.String

Full name: Microsoft.FSharp.Core.string

union case EmailAddress.InvalidEmail: string -> EmailAddress

val ofString : _arg1:string -> EmailAddress

Full name: Script.Email.ofString

val invalid : string

val email : string

module Email

from Script

val invalid : EmailAddress

Full name: Script.invalid

val valid : EmailAddress

Full name: Script.valid

active recognizer InvalidEmail: EmailAddress -> Choice<string,string>

Full name: Script.Email.( |ValidEmail|InvalidEmail| )

val printfn : format:Printf.TextWriterFormat<'T> -> 'T

Full name: Microsoft.FSharp.Core.ExtraTopLevelOperators.printfn

active recognizer ValidEmail: EmailAddress -> Choice<string,string>

Full name: Script.Email.( |ValidEmail|InvalidEmail| )

val valid : string

Raw view Test code New version

More information

Link:	http://fssnip.net/ma
Posted:	10 years ago
Author:	iceypoi
Tags:	language