| Let(d, e2) -> (match d with
                    | [] -> eval e2
                    | dec1::decs -> (match dec1 with
                        | Val (ex,na) -> eval (Let(decs, subst (eval ex, na) e2))
                        | ByName (ex,na) -> eval (Let(decs, subst (ex,na) e2))
                        | Valtuple (Tuple (ex), nList) -> eval (Let (decs, substList (zip (evalList ex) nList) e2))
                        | Valtuple (_,_) -> raise (Stuck "Bad expression for a ValTuple") ))