+
+let rec seq = function
+ (* TODO: Is appending 0 OK? How else can the empty case be handled? *)
+ | [] -> T.EXP (T.CONST 0)
+ | s :: ss -> T.SEQ (s, seq ss)
+
+let cond_stm gen_stm =
+ let t = Temp.Label.gen () in
+ let f = Temp.Label.gen () in
+ let r = Temp.Temp.gen () in
+ let stms =
+ [ T.MOVE (T.TEMP r, T.CONST 1)
+ ; gen_stm (t, f)
+ ; T.LABEL f
+ ; T.MOVE (T.TEMP r, T.CONST 0)
+ ; T.LABEL t
+ ]
+ in
+ (seq stms, T.TEMP r)
+
+let unEx = function
+ | Ex exp -> exp
+ | Nx stm -> T.ESEQ (stm, T.CONST 0)
+ | Cx gen ->
+ let stm, exp = cond_stm gen in
+ T.ESEQ (stm, exp)
+
+let unNx = function
+ | Ex exp -> T.EXP exp
+ | Nx stm -> stm
+ | Cx gen -> fst (cond_stm gen)
+
+let unCx = function
+ (* "should never occur in compiling a well typed Tiger program" p.154 *)
+ | Nx _ -> assert false
+ | Ex e -> fun (_, _) -> T.EXP e (* TODO: Is this right? *)
+ | Cx g -> g
+
+let dummy__FIXME = Ex (T.CONST 0)