CODEWITHSUNDEEP
f#
FZed
FZed

Reputation: 528

Algebraic data types containing class types in F#

Algebraic data types are represented in F# by using Sum (Discriminated Unions) and product (tuples) types. I can then combine these elements as in algebra.

I can also define a tuple of two class types like this :

type MINT (i:int) =
    member x.i = i

type MINTtuple = MINT * MINT

let  v :MINTtuple= MINT(42), MINT(43)

(fst v).i |> printfn "%d" |> ignore

But I cannot seem to define a DU containing class types like this or any other syntax I could think of after looking at some documentation :

type MINTDU = 
    |Positive of MINT
    |Negative of MINT
let w = Positive MINT(45)

My question : if it is not possible, what are the fundamental reasons ? I am very happy with F# features as they are. I only want to better understand what are the tensions between functional types and class types. Thanks.

Upvotes: 0

Views: 189

Answers (1)

Kevin
Kevin

Reputation: 2291

You just need some brackets. Try this:

let createPositiveMint i =
    Positive (MINT i)

If you don't want a separate function as in your sample it would just be

let w = Positive (MINT 45)

Edited as per @kaefer suggestion.

Upvotes: 1

Related Questions