proposition: Lemma eval_If e : let ev := qf_eval e in ev If = (if ev pred_f then ev then_f else ev else_f).
proof: Proof. by rewrite /=; case: ifP => _; rewrite ?orbF. Qed.
imports: HB(structures) mathcomp(ssreflect ssrfun ssrbool eqtype ssrnat div seq) mathcomp(choice fintype finfun bigop prime binomial)