+fun registerPre f =
+ let
+ val old = !pr
+ in
+ pr := (fn () => (old (); f ()))
+ end
+fun pre () = !pr ()
+
+end
+
+local
+ val pst = ref (fn () => ())
+in
+
+fun registerPost f =
+ let
+ val old = !pst
+ in
+ pst := (fn () => (old (); f ()))
+ end
+fun post () = !pst ()
+
+end
+
+local
+ val pr = ref (fn () => ())
+in
+
+fun registerPreTycheck f =
+ let
+ val old = !pr
+ in
+ pr := (fn () => (old (); f ()))
+ end
+fun preTycheck () = !pr ()
+
+end
+
+fun badArgs (name, args) =
+ (print ("Invalid arguments to " ^ name ^ "\n");
+ app (fn arg => Print.preface ("Argument: ", Print.p_exp arg)) args;
+ raise Domain)
+fun badArg (func, arg, v) =
+ (print ("Invalid " ^ arg ^ " argument to " ^ func ^ "\n");
+ Print.preface ("Argument: ", Print.p_exp v);
+ raise Domain)
+
+type 'a arg = exp -> 'a option
+
+fun int (EInt n, _) = SOME n
+ | int _ = NONE
+
+fun string (EString s, _) = SOME s
+ | string _ = NONE
+
+fun bool (EVar "false", _) = SOME false
+ | bool (EVar "true", _) = SOME true
+ | bool _ = NONE
+
+fun mapFail f [] = SOME []
+ | mapFail f (h :: t) =
+ case f h of
+ NONE => NONE
+ | SOME h' =>
+ case mapFail f t of
+ NONE => NONE
+ | SOME t' => SOME (h' :: t')
+
+fun list f (EList ls, _) = mapFail f ls
+ | list _ _ = NONE
+
+fun none func f (_, []) = (f ();
+ SM.empty)
+ | none func _ (_, es) = badArgs (func, es)
+
+fun one func (name, arg) f (_, [e]) =
+ (case arg e of
+ NONE => badArg (func, name, e)
+ | SOME v => (f v;
+ SM.empty))
+ | one func _ _ (_, es) = badArgs (func, es)
+
+fun two func (name1, arg1, name2, arg2) f (_, [e1, e2]) =
+ (case (arg1 e1, arg2 e2) of
+ (NONE, _) => badArg (func, name1, e1)
+ | (_, NONE) => badArg (func, name2, e2)
+ | (SOME v1, SOME v2) => (f (v1, v2);
+ SM.empty))
+ | two func _ _ (_, es) = badArgs (func, es)
+
+fun three func (name1, arg1, name2, arg2, name3, arg3) f (_, [e1, e2, e3]) =
+ (case (arg1 e1, arg2 e2, arg3 e3) of
+ (NONE, _, _) => badArg (func, name1, e1)
+ | (_, NONE, _) => badArg (func, name2, e2)
+ | (_, _, NONE) => badArg (func, name3, e3)
+ | (SOME v1, SOME v2, SOME v3) => (f (v1, v2, v3);
+ SM.empty))
+ | three func _ _ (_, es) = badArgs (func, es)
+
+fun oneV func (name, arg) f (evs, [e]) =
+ (case arg e of
+ NONE => badArg (func, name, e)
+ | SOME v => (f (evs, v);
+ SM.empty))
+ | oneV func _ _ (_, es) = badArgs (func, es)
+
+fun twoV func (name1, arg1, name2, arg2) f (evs, [e1, e2]) =
+ (case (arg1 e1, arg2 e2) of
+ (NONE, _) => badArg (func, name1, e1)
+ | (_, NONE) => badArg (func, name2, e2)
+ | (SOME v1, SOME v2) => (f (evs, v1, v2);
+ SM.empty))
+ | twoV func _ _ (_, es) = badArgs (func, es)
+
+
+fun env arg (evs, name) =
+ case SM.find (evs, name) of
+ NONE => raise Fail ("Unavailable environment variable " ^ name)
+ | SOME e =>
+ case arg e of
+ NONE => (Print.preface ("Unexpected value for " ^ name ^ ":",
+ Print.p_exp e);
+ raise Fail ("Bad format for environment variable " ^ name))
+ | SOME v => v
+
+fun type_one func arg f =
+ registerType (func, fn e =>
+ case arg e of
+ NONE => false
+ | SOME v => f v)
+
+fun action_none name f = registerAction (name, none name f)
+fun action_one name args f = registerAction (name, one name args f)
+fun action_two name args f = registerAction (name, two name args f)
+fun action_three name args f = registerAction (name, three name args f)
+
+fun actionV_none name f = registerAction (name, fn (env, _) => (f env; env))
+fun actionV_one name args f = registerAction (name, oneV name args f)
+fun actionV_two name args f = registerAction (name, twoV name args f)
+
+fun container_none name (f, g) = registerContainer (name, none name f, g)
+fun container_one name args (f, g) = registerContainer (name, one name args f, g)
+
+fun containerV_one name args (f, g) = registerContainer (name, oneV name args f, g)
+
+type env = SS.set * (typ * exp option) SM.map * SS.set
+val empty : env = (SS.empty, SM.empty, SS.empty)
+
+fun lookupType (ts, _, _) name = SS.member (ts, name)
+fun lookupVal (_, vs, _) name =