Demonstrate ad-hoc polymorphism in F#. It uses inline function with Statically Resolved Type Parameters feature. Try it in [repl.it](https://replit.com/@ruxozheng/F-Ad-hoc-polymorphism)

Program.fs

// From: https://angrydexterous.github.io/typeclassish.html

type Num<'A> =
  abstract member Add: 'A -> 'A -> 'A
  abstract member Subtract: 'A -> 'A -> 'A

[<Struct; NoComparison; NoEquality>]
type TInt =
  interface Num<int> with
    member my.Add x y = x + y
    member my.Subtract x y = x - y
    
[<Struct; NoComparison; NoEquality>]
type TFloat =
  interface Num<float> with
    member my.Add x y = x + y
    member my.Subtract x y = x - y

[<Struct; NoComparison; NoEquality>]
type Num =
  static member inline ($) (_: Num, _: int) = Unchecked.defaultof<TInt>
  static member inline ($) (_: Num, _: float) = Unchecked.defaultof<TFloat>

let inline num (x: 'a) :^m when ^m :> Num<'a> = Unchecked.defaultof<Num> $ x
let inline doubleX x = (num x).Add x x

printfn $"Result = {doubleX 20}"
printfn $"Result = {doubleX 1.23}"