tabulators

[Stephen Weeks]

> > signature ITERATE1 =
> >    sig
> >       type 'a t
> >       val iterate: 'a t -> 'a -> unit
> >    end
> 
> It doesn't look like I can do much of anything with that.

Duh!  :-)  That should be

signature ITERATE1 =
  sig
     type 'a t
     val iterate: 'a t -> unit -> 'a
  end