+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)