(** The [apply_binds_dom_contradiction] tactic solves a goal by
      applying the [binds_dom_contradiction] lemma.  The tactic
      succeeds only if the the hypotheses of the lemma are immediately
      satisfied. *)

  Ltac apply_binds_dom_contradiction :=
    match goal with
      | H : binds ?x ?a ?E, J : ?x `notin` (dom ?E) |- _ =>
        assert False by apply (@binds_dom_contradiction _ _ _ _ H J);
        intuition
      | H : binds ?x ?a ?E, J : ?x `in` (dom ?E) -> False |- _ =>
        assert False by apply (@binds_dom_contradiction _ _ _ _ H J);
        intuition
    end.(** The [solve_binds] tactic attempts to solve goals about [binds].
      Given its definition, it's likely to work only when the
      hypotheses in the goal already contain all the relevant [binds]
      propositions.  Thus, the tactic may not be generally useful.  It
      is useful, however, for proving facts about [binds] such as the
      ones below. *)

  Ltac solve_binds :=
    simpl_asnlist in *;
    autorewrite with rewr_binds in *;
    intuition (auto || fsetdec || apply_binds_dom_contradiction)
    || fail.(** The tactics [analyze_binds] and [analyze_binds_uniq] tactics
      take as an argument a hypotheses about [binds] and perform a
      case analysis based on the structure of the association list.
      In the case of [analyze_binds_uniq], the analysis is performed
      assuming that the association list is [uniq].  The lemmas
      [binds_app] and [binds_app_uniq] are examples of such case
      analysis.

      Implementation notes:

        - The initial calls to [simpl_asnlist] put the relevant
          association lists into normal form.
        - In the case of [binds_app_uniq], we assert that the
          association list is [uniq].  This enables the [autorewrite]
          step to succeed.
        - Rather than work on [H] itself, we copy it and work on the
          copy.  Thus, in instances where the analysis leaves unsolved
          subgoals, it is still possible to see the original
          hypothesis.
        - The rest of the tactic breaks apart the copy of H and tries
          several simple means for solving the resulting subgoals. *)

  Ltac analyze_binds H :=
    simpl_asnlist;
    simpl_asnlist in H;
    match type of H with
      | binds ?x ?a ?E =>
        let J := fresh in
        pose proof H as J;
        autorewrite with rewr_binds in J;
        simpl_asnlist in J;
        try (progress decompose [and or] J; clear J);
        try solve [trivial | discriminate | intuition | fsetdec]
    end.Ltac analyze_binds_uniq H :=
    simpl_asnlist;
    simpl_asnlist in H;
    match type of H with
      | binds ?x ?a ?E =>
        match goal with
          | H : uniq ?E |- _ => idtac
          | _ => assert (uniq E); [ try solve_uniq | ]
        end;
        let J := fresh in
        pose proof H as J;
        autorewrite with rewr_binds_uniq in J;
        simpl_asnlist in J;
        try (progress decompose [and or] J; clear J);
        try solve [trivial | discriminate | intuition | fsetdec]
    end.

Lemma binds_weaken : binds x a (E ++ G) -> binds x a (E ++ F ++ G).