(** Here's an example of how you could use these lemmas.
    Suppose you have this simple program, [(if a <? 5 then a else 2)],
    and you want to prove that it evaluates to a number smaller than 6.
    You can use [blt_reflect] "by hand": *)
    
Example reflect_example1: forall a, (if a<?5 then a else 2) < 6.(** Our high-tech _boolean destruction_ tactic: *)

Ltac bdestruct X :=
  let H := fresh in let e := fresh "e" in
   evar (e: Prop);
   assert (H: reflect e X); subst e;
    [eauto with bdestruct
    | destruct H as [H|H];
       [ | try first [apply not_lt in H | apply not_le in H]]].(** Here's a brief example of how to use [bdestruct].  There
     are more examples later. *)

Example reflect_example2: forall a, (if a<?5 then a else 2) < 6.(* ================================================================= *)
(** ** [inversion] / [clear] / [subst] *)
(** Coq's [inversion H] tactic is so good at extracting information
    from the hypothesis [H] that [H] becomes completely redundant,
    and one might as well [clear] it from the goal.  Then, since the
    [inversion] typically creates some equality facts, why not then
    [subst] ?   This motivates the following useful tactic, [inv]:  *)

Ltac inv H := inversion H; clear H; subst.

Theorem bogus_subtraction: ~ (forall k:nat, k > k - 3).