proposition: Lemma nat_fun_ev n: Vf nat_fun (Ro n) = (Ro n.+1).
proof: Proof. have rs: (inc (Ro n) (source nat_fun)). rewrite /nat_fun; aw; apply: R_inc. move: (Vf_pr3 (nat_fun_function) rs) => /nat_map_P [u eql]. by rewrite (pr2_def eql) (R_inj (pr1_def eql)). Qed.
imports: mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat)