Ltac flatten_bool :=
  repeat match goal with
           [ id : (_ && _)%bool = true |- _ ] =>  destruct (andb_prop _ _ id); clear id
         |  [ id : (_ || _)%bool = true |- _ ] =>  destruct (orb_prop _ _ id); clear id
         end.Ltac inv H := inversion H ; try subst ; clear H.

Lemma le_neg : forall x, ((0 <= x) -> False) <-> 0 < -x.