Parameterless lambda expressions in F#

Question

I am looking for a way to define Parameterless lambda expressions in F#, much like the following C# example.

var task = () => {
                     int x = 3;
                     DoSomething(x);
                 }

I tried the following

let task = fun _ -> 
              let x = 3
              doSomething x

It compiles but it gives me task : ('a -> unit) what I am actually looking for is task : (unit -> unit)

The MSDN Documentation does not talk about this. What am I missing here ?

Answer 1

it's just

let task = fun () -> // whatever you need

you example would be:

let task = fun () ->
              let x = 3
              DoSomething(3)

assuming DoSomething is of type int -> unit - if it returns something else you need

let task = fun () ->
              let x = 3
              DoSomething(3) |> ignore

to get type unit -> unit

Remark: Usually you don't write let task = fun () -> ... but just let task() = ...

The thing you missed: if you write fun _ -> () you are saying you want to take some parameter that you don't mind about - so F# will take the most general (being named 'a here) - this would include unit! () is the only value of type unit (more or less void from C# ... but a true type in F#)