Custom comparison

[joshua-light]

Hi!
I'm trying to design a safe type called Nat that represents a natural number (1, 2, 3, etc.). Something like this:

type Nat =
    private | Nat of int
    
    static member One = Nat 1
    
    static member New (x: int) : Nat option =
        if x > 0
        then Some (Nat x)
        else None
        
    static member (+) (Nat a, Nat b) = Nat (a + b)
    static member (-) (Nat a, Nat b) = Nat.New (a - b)
    static member (*) (Nat a, Nat b) = Nat (a * b)
    static member (/) (Nat a, Nat b) = Nat (a / b)

Since this type is a simple int wrapper, it's reasonable to define some operators overloaded for int, for example:

static member (+) (Nat a, b: int)  = Nat.New (a + b)

Now consider you have an object x with field Count: Nat and you simply want to check whether x.Count > 1. It seems like it's impossible (but makes sense) to overload equality or comparison operator:

static member (=) (Nat a, b: int) = a = b // Error

Is there any workaround to do something like that?
This can be solved partially by implementing implicit cast from Nat to int (which is totally reasonable) and then comparing in reverse order (e.g. 1 < x.Count). But it's not readable in the same way as the first option.

Thanks in advance!

P.S. While it's perfectly possible to define a custom operator or a function (e.g. x.Count |> gt 1), it'd be much more convenient to use the same syntax for custom types without additional noise.

[dsyme]

There is no direct way to overload= in F#. You could define your own operator. You might also get some mileage from an op_Implicit. However neither are really that recommended (they make code harder to understand, and you should probably just really accept a tax of an explicit coercion for converting int --> Nat.