Generic Monadic Map and Join using statically resolved type variables

let inline mapM b f m =       

    let unit x    = (^x: (member Return: ^b -> ^n) b, x)  

    let (>>=) m f = (^x: (member Bind: ^m -> (^a -> ^n) -> ^n) b, m, f)

    m >>= (fun x -> unit (f x))

let inline joinM b m =          

    let (>>=) m f = (^x: (member Bind: ^m -> (^n -> ^n) -> ^n) b, m, f)

    m >>= id