fact: Fixpoint to_expr (e: regex): expr_(BKA) (fun _ => xH) (fun _ => xH) xH xH := match e with | r_zer => 0 | r_one => 1 | r_pls e f => to_expr e + to_expr f | r_dot e f => to_expr e ⋅ to_expr f | r_str e => (to_expr e)^* | r_var a => e_var a end.
imports: syntax kleene boolean lang lset sums normalisation