+(*
+\ 5h1\ 6Broadcasting points\ 5/h1\ 6
+Intuitively, a regular expression e must be understood as a pointed expression with a single
+point in front of it. Since however we only allow points before symbols, we must broadcast
+this initial point inside e traversing all nullable subexpressions, that essentially corresponds
+to the ϵ-closure operation on automata. We use the notation •(_) to denote such an operation;
+its definition is the expected one: let us start discussing an example.
+
+\ 5b\ 6Example\ 5/b\ 6
+Let us broadcast a point inside (a + ϵ)(b*a + b)b. We start working in parallel on the
+first occurrence of a (where the point stops), and on ϵ that gets traversed. We have hence
+reached the end of a + ϵ and we must pursue broadcasting inside (b*a + b)b. Again, we work in
+parallel on the two additive subterms b^*a and b; the first point is allowed to both enter the
+star, and to traverse it, stopping in front of a; the second point just stops in front of b.
+No point reached that end of b^*a + b hence no further propagation is possible. In conclusion:
+ •((a + ϵ)(b^*a + b)b) = 〈(•a + ϵ)((•b)^*•a + •b)b, false〉
+*)
+
+
include "tutorial/chapter7.ma".
definition lo ≝ λS:DeqSet.λa,b:pre S.〈\fst a + \fst b,\snd a ∨ \snd b〉.
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