type [<Measure>] b
 
type Vec<'a, [<Measure>] 'n> = 
    | V of List<'a>
 
let nil<'a> : Vec<'a, 1> =
    V([])
 
let cons (x : 'a) (V(xs) : Vec<'a,'n>) : Vec<'a,'n b> =
    V(x :: xs)
 
let append (V(xs) : Vec<'a,'n>) (V(ys) : Vec<'a,'m>) : Vec<'a,'n 'm> =
    V(xs @ ys)
 
let zip (V(xs) : Vec<'a,'n>) (V(ys) : Vec<'b,'n>) : Vec<'a * 'b,'n> =
    V(List.zip xs ys)
 
let sum (V(xs) : Vec<int,'n>) : int = 
    List.sum xs
 
let l = cons 1 (cons 2 (cons 3 nil))
let g = zip l l

(*
error FS0001: Type mismatch. Expecting a
    Vec<int,1>    
but given a
    Vec<int,b ^ 3>    
The unit of measure '1' does not match the unit of measure 'b ^ 3' 
*)
//let h = zip l (append l l)
 
printfn "%A" l
printfn "%A" g