[Ur] stateful structure?

[Adam Chlipala]

Marc Weber wrote:
> You want this interface instead:
> structure Stateful =
> struct
>    val init : {} ->  transaction counter_id
>    val increment : counter_id ->  transaction xbody
> end
>    

I think a line [type counter_id] should be added to the signature.  
Also, there's a parsing error here; you probably meant [: sig] instead 
of [= struct].  Beside that, this is the approach I had in mind.

Without using the FFI, it is not possible to store [source]s in global 
state.