+
+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 => raise Fail ("Bad format for environment variable " ^ name)
+ | SOME v => v
+