Ltac rewrite_refl_id := autorewrite with refl_id.(** Clear the context and goal of equality proofs. *)

Ltac clear_eq_ctx :=
  rewrite_refl_id ; clear_eq_proofs.(** Reapeated elimination of [eq_rect] applications.
   Abstracting equalities makes it run much faster than an naive implementation. *)

Ltac simpl_eqs :=
  repeat (elim_eq_rect ; simpl ; clear_eq_ctx).(** Clear unused reflexivity proofs. *)

Ltac clear_refl_eq :=
  match goal with [ H : ?X = ?X |- _ ] => clear H end.Ltac clear_refl_eqs := repeat clear_refl_eq.(** Clear unused equality proofs. *)

Ltac clear_eq :=
  match goal with [ H : _ = _ |- _ ] => clear H end.Ltac clear_eqs := repeat clear_eq.(** Combine all the tactics to simplify goals containing coercions. *)

Ltac simplify_eqs :=
  simpl ; simpl_eqs ; clear_eq_ctx ; clear_refl_eqs ;
    try subst ; simpl ; repeat simpl_uip ; rewrite_refl_id.(** A tactic that tries to remove trivial equality guards in induction hypotheses coming
   from [dependent induction]/[generalize_eqs] invocations. *)

Ltac simplify_IH_hyps := repeat
  match goal with
    | [ hyp : context [ block _ ] |- _ ] =>
      specialize_eqs hyp
  end.(** We split substitution tactics in the two directions depending on which
   names we want to keep corresponding to the generalization performed by the
   [generalize_eqs] tactic. *)

Ltac subst_left_no_fail :=
  repeat (match goal with
            [ H : ?X = ?Y |- _ ] => subst X
          end).Ltac subst_right_no_fail :=
  repeat (match goal with
            [ H : ?X = ?Y |- _ ] => subst Y
          end).Ltac inject_left H :=
  progress (inversion H ; subst_left_no_fail ; clear_dups) ; clear H.Ltac inject_right H :=
  progress (inversion H ; subst_right_no_fail ; clear_dups) ; clear H.Ltac autoinjections_left := repeat autoinjection ltac:(inject_left).Ltac autoinjections_right := repeat autoinjection ltac:(inject_right).Ltac simpl_depind := subst_no_fail ; autoinjections ; try discriminates ;
  simpl_JMeq ; simpl_existTs ; simplify_IH_hyps.Ltac simpl_depind_l := subst_left_no_fail ; autoinjections_left ; try discriminates ;
  simpl_JMeq ; simpl_existTs ; simplify_IH_hyps.Ltac simpl_depind_r := subst_right_no_fail ; autoinjections_right ; try discriminates ;
  simpl_JMeq ; simpl_existTs ; simplify_IH_hyps.Ltac blocked t := block_goal ; t ; unblock_goal.(** The [DependentEliminationPackage] provides the default dependent elimination principle to
   be used by the [equations] resolver. It is especially useful to register the dependent elimination
   principles for things in [Prop] which are not automatically generated. *)

Class DependentEliminationPackage (A : Type) :=
  { elim_type : Type ; elim : elim_type }.(** The [DependentEliminationPackage] provides the default dependent elimination principle to
   be used by the [equations] resolver. It is especially useful to register the dependent elimination
   principles for things in [Prop] which are not automatically generated. *)

Class DependentEliminationPackage (A : Type) :=
  { elim_type : Type ; elim : elim_type }.(** The [DependentEliminationPackage] provides the default dependent elimination principle to
   be used by the [equations] resolver. It is especially useful to register the dependent elimination
   principles for things in [Prop] which are not automatically generated. *)

Class DependentEliminationPackage (A : Type) :=
  { elim_type : Type ; elim : elim_type }.(** A higher-order tactic to apply a registered eliminator. *)

Ltac elim_tac tac p :=
  let ty := type of p in
  let eliminator := eval simpl in (@elim _ (_ : DependentEliminationPackage ty)) in
    tac p eliminator.(** Specialization to do case analysis or induction.
   Note: the [equations] tactic tries [case] before [elim_case]: there is no need to register
   generated induction principles. *)

Ltac elim_case p := elim_tac ltac:(fun p el => destruct p using el) p.Ltac elim_ind p := elim_tac ltac:(fun p el => induction p using el) p.

Lemma deletion A B (t : A) : B -> (t = t -> B).