Comment.

demos/brz/Brzozowski.ml

@@ -249,6 +249,10 @@ let (&&&) e1 e2 =
 
 (* Negation. *)
 
+(* One could systematically push negation down through conjunction (turning it
+   into a disjunction) and through disjunction (turning into a conjunction). It
+   is done here only in the case of empty conjunctions and disjunctions. *)
+
 let neg (e : regexp) : regexp =
   match skeleton e with
   | ENeg e ->