anchor.diff:  //IN F*: type atom : Type0 =
   type atom = //JUST FSHARP
     | Var of var
  -  | Type of universe
  +  | Type of universe //Zoe: Not sure why this need to be an atom, just following the paper
  +  | Inductive of fv
     | Match of t * (* the scutinee *)
                (t -> t) (* the closure that pattern matches the scrutiny *) 
     | Rec of letbinding * list<t> (* Danel: This wraps a unary F* rec. def. as a thunk in F# *)
  
positive.code:     | Tm_bvar db -> //de Bruijn
        List.nth bs db.index
  
      //| Tm_fvar _ -> debug_term e; failwith "Tm_fvar: Not yet implemented"
  
      | Tm_uinst _ -> debug_term e; failwith "Tm_uinst: Not yet implemented"
  
      | Tm_type u -> mkAccTyp u
  
negative.code: open FStar
  open FStar.TypeChecker
  open FStar.Syntax.Syntax
  open FStar.Ident
    
  module S = FStar.Syntax.Syntax
  module SS = FStar.Syntax.Subst
  module Range = FStar.Range
  