+(*
+Example. Let us consider the item
+
+ (•a + ϵ)((•b)*•a + •b)b
+
+and the two moves w.r.t. the characters a and b.
+For a, we have two possible positions (all other points gets erased); the innermost
+point stops in front of the final b, while the other one broadcast inside (b^*a + b)b,
+so
+
+ move((•a + ϵ)((•b)*•a + •b)b,a) = 〈(a + ϵ)((•b)^*•a + •b)•b, false〉
+
+For b, we have two positions too. The innermost point stops in front of the final b too,
+while the other point reaches the end of b* and must go back through b*a:
+
+ move((•a + ϵ)((•b)*•a + •b)b ,b) = 〈(a + ϵ)((•b)*•a + b)•b, false〉
+
+*)
+