Library AAC_tactics.AAC


Theory file for the aac_rewrite tactic

We define several base classes to package associative and possibly commutative operators, and define a data-type for reified (or quoted) expressions (with morphisms).
We then define a reflexive decision procedure to decide the equality of reified terms: first normalise reified terms, then compare them. This allows us to close transitivity steps automatically, in the aac_rewrite tactic.
We restrict ourselves to the case where all symbols operate on a single fixed type. In particular, this means that we cannot handle situations like
H: ∀ x y, nat_of_pos (pos_of_nat (x) + y) + x = ....
where one occurrence of + operates on nat while the other one operates on positive.

Require Import Arith NArith.
Require Import List.
Require Import FMapPositive FMapFacts.
Require Import RelationClasses Equality.
Require Export Morphisms.

From AAC_tactics
Require Import Utils.

Set Implicit Arguments.
Set Asymmetric Patterns.

Local Open Scope signature_scope.

Environments for the reification process: we use positive maps to index elements


Section sigma.
  Definition sigma := PositiveMap.t.
  Definition sigma_get A (null : A) (map : sigma A) (n : positive) : A :=
    match PositiveMap.find n map with
      | None ⇒ null
      | Some x ⇒ x
    end.
  Definition sigma_add := @PositiveMap.add.
  Definition sigma_empty := @PositiveMap.empty.
End sigma.

Classes for properties of operators


Class Associative (X:Type) (R:relation X) (dot: X → X → X) :=
  law_assoc : ∀ x y z, R (dot x (dot y z)) (dot (dot x y) z).
Class Commutative (X:Type) (R: relation X) (plus: X → X → X) :=
  law_comm: ∀ x y, R (plus x y) (plus y x).
Class Unit (X:Type) (R:relation X) (op : X → X → X) (unit:X) := {
  law_neutral_left: ∀ x, R (op unit x) x;
  law_neutral_right: ∀ x, R (op x unit) x
}.

Class used to find the equivalence relation on which operations are A or AC, starting from the relation appearing in the goal

Class AAC_lift X (R: relation X) (E : relation X) := {
  aac_lift_equivalence : Equivalence E;
  aac_list_proper : Proper (E ==> E ==> iff) R
}.

simple instances, when we have a subrelation, or an equivalence

Instance aac_lift_subrelation {X} {R} {E} {HE: Equivalence E}
  {HR: @Transitive X R} {HER: subrelation E R}: AAC_lift R E | 3.
Proof.
  constructor; trivial.
  intros ? ? H ? ? H'. split; intro G.
   rewrite <- H, G. apply HER, H'.
   rewrite H, G. apply HER. symmetry. apply H'.
Qed.

Instance aac_lift_proper {X} {R : relation X} {E} {HE: Equivalence E}
  {HR: Proper (E==>E==>iff) R}: AAC_lift R E | 4 := {}.

Module Internal.

Utilities for the evaluation function


Section copy.

  Context {X} {R} {HR: @Equivalence X R} {plus}
   (op: Associative R plus) (op': Commutative R plus) (po: Proper (R ==> R ==> R) plus).

  Fixpoint copy' n x := match n with
                         | xH ⇒ x
                         | xI n ⇒ let xn := copy' n x in plus (plus xn xn) x
                         | xO n ⇒ let xn := copy' n x in (plus xn xn)
                       end.
  Definition copy n x := Prect (fun _ ⇒ X) x (fun _ xn ⇒ plus x xn) n.

  Lemma copy_plus : ∀ n m x, R (copy (n+m) x) (plus (copy n x) (copy m x)).
  Proof.
    unfold copy.
    induction n using Pind; intros m x.
     rewrite Prect_base. rewrite <- Pplus_one_succ_l. rewrite Prect_succ. reflexivity.
     rewrite Pplus_succ_permute_l. rewrite 2Prect_succ. rewrite IHn. apply op.
  Qed.
  Lemma copy_xH : ∀ x, R (copy 1 x) x.
  Proof. intros; unfold copy; rewrite Prect_base. reflexivity. Qed.
  Lemma copy_Psucc : ∀ n x, R (copy (Pos.succ n) x) (plus x (copy n x)).
  Proof. intros; unfold copy; rewrite Prect_succ. reflexivity. Qed.

  Global Instance copy_compat n: Proper (R ==> R) (copy n).
  Proof.
    unfold copy.
    induction n using Pind; intros x y H.
     rewrite 2Prect_base. assumption.
     rewrite 2Prect_succ. apply po; auto.
  Qed.

End copy.

Packaging structures

free symbols


Module Sym.
  Section t.
    Context {X} {R : relation X} .

type of an arity
    Fixpoint type_of (n: nat) :=
      match n with
        | O ⇒ X
        | S n ⇒ X → type_of n
      end.

relation to be preserved at an arity
    Fixpoint rel_of n : relation (type_of n) :=
      match n with
        | O ⇒ R
      | S n ⇒ respectful R (rel_of n)
      end.

a symbol package contains an arity, a value of the corresponding type, and a proof that the value is a proper morphism
  Record pack : Type := mkPack {
    ar : nat;
    value :> type_of ar;
    morph : Proper (rel_of ar) value
  }.

helper to build default values, when filling reification environments
  Definition null: pack := mkPack 1 (fun x ⇒ x) (fun _ _ H ⇒ H).

  End t.

End Sym.

binary operations


Module Bin.
  Section t.
    Context {X} {R: relation X}.

    Record pack := mk_pack {
      value:> X → X → X;
      compat: Proper (R ==> R ==> R) value;
      assoc: Associative R value;
      comm: option (Commutative R value)
    }.
  End t.

End Bin.

Reification, normalisation, and decision


Section s.
  Context {X} {R: relation X} {E: @Equivalence X R}.
  Infix "==" := R (at level 80).


  Variable e_sym: idx → @Sym.pack X R.
  Variable e_bin: idx → @Bin.pack X R.


packaging units (depends on e_bin)

  Record unit_of u := mk_unit_for {
    uf_idx: idx;
    uf_desc: Unit R (Bin.value (e_bin uf_idx)) u
  }.

  Record unit_pack := mk_unit_pack {
    u_value:> X;
    u_desc: list (unit_of u_value)
  }.
  Variable e_unit: positive → unit_pack.

  Hint Resolve e_bin e_unit: typeclass_instances.

Almost normalised syntax

a term in T is in normal form if:
  • sums do not contain sums
  • products do not contain products
  • there are no unary sums or products
  • lists and msets are lexicographically sorted according to the order we define below
vT n denotes the set of term vectors of size n (the mutual dependency could be removed),
Note that T and vT depend on the e_sym environment (which contains, among other things, the arity of symbols)

  Inductive T: Type :=
  | sum: idx → mset T → T
  | prd: idx → nelist T → T
  | sym: ∀ i, vT (Sym.ar (e_sym i)) → T
  | unit : idx → T
  with vT: nat → Type :=
  | vnil: vT O
  | vcons: ∀ n, T → vT n → vT (S n).

lexicographic rpo over the normalised syntax
  Fixpoint compare (u v: T) :=
    match u,v with
      | sum i l, sum j vs ⇒ lex (idx_compare i j) (mset_compare compare l vs)
      | prd i l, prd j vs ⇒ lex (idx_compare i j) (list_compare compare l vs)
      | sym i l, sym j vs ⇒ lex (idx_compare i j) (vcompare l vs)
      | unit i , unit j ⇒ idx_compare i j
      | unit _ , _ ⇒ Lt
      | _ , unit _ ⇒ Gt
      | sum _ _, _ ⇒ Lt
      | _ , sum _ _ ⇒ Gt
      | prd _ _, _ ⇒ Lt
      | _ , prd _ _ ⇒ Gt

    end
  with vcompare i j (us: vT i) (vs: vT j) :=
    match us,vs with
      | vnil, vnil ⇒ Eq
      | vnil, _ ⇒ Lt
      | _, vnil ⇒ Gt
      | vcons _ u us, vcons _ v vs ⇒ lex (compare u v) (vcompare us vs)
    end.

Evaluation from syntax to the abstract domain


  Fixpoint eval u: X :=
    match u with
      | sum i l ⇒ let o := Bin.value (e_bin i) in
        fold_map (fun un ⇒ let '(u,n):=un in @copy _ o n (eval u)) o l
      | prd i l ⇒ fold_map eval (Bin.value (e_bin i)) l
      | sym i v ⇒ eval_aux v (Sym.value (e_sym i))
      | unit i ⇒ e_unit i
    end
  with eval_aux i (v: vT i): Sym.type_of i → X :=
    match v with
      | vnil ⇒ fun f ⇒ f
      | vcons _ u v ⇒ fun f ⇒ eval_aux v (f (eval u))
    end.

we need to show that compare reflects equality (this is because we work with msets rather than lists with arities)
  Lemma tcompare_weak_spec: ∀ (u v : T), compare_weak_spec u v (compare u v)
  with vcompare_reflect_eqdep: ∀ i us j vs (H: i=j), vcompare us vs = Eq → cast vT H us = vs.
  Proof.
    induction u.
     destruct v; simpl; try constructor.
      case (pos_compare_weak_spec p p0); intros; try constructor.
      case (mset_compare_weak_spec compare tcompare_weak_spec m m0); intros; try constructor.
     destruct v; simpl; try constructor.
      case (pos_compare_weak_spec p p0); intros; try constructor.
      case (list_compare_weak_spec compare tcompare_weak_spec n n0); intros; try constructor.
     destruct v0; simpl; try constructor.
      case_eq (idx_compare i i0); intro Hi; try constructor.
      apply idx_compare_reflect_eq in Hi. symmetry in Hi. subst.       case_eq (vcompare v v0); intro Hv; try constructor.
      rewrite <- (vcompare_reflect_eqdep _ _ _ _ eq_refl Hv). constructor.
     destruct v; simpl; try constructor.
      case_eq (idx_compare p p0); intro Hi; try constructor.
      apply idx_compare_reflect_eq in Hi. symmetry in Hi. subst. constructor.

    induction us; destruct vs; simpl; intros H Huv; try discriminate.
     apply cast_eq, eq_nat_dec.
     injection H; intro Hn.
     revert Huv; case (tcompare_weak_spec t t0); intros; try discriminate.
     symmetry in Hn. subst.      rewrite <- (IHus _ _ eq_refl Huv).
     apply cast_eq, eq_nat_dec.
  Qed.

  Instance eval_aux_compat i (l: vT i): Proper (@Sym.rel_of X R i ==> R) (eval_aux l).
  Proof.
    induction l; simpl; repeat intro.
     assumption.
     apply IHl, H. reflexivity.
  Qed.


  Definition is_unit_of j i :=
    List.existsb (fun p ⇒ eq_idx_bool j (uf_idx p)) (u_desc (e_unit i)).

  Definition is_commutative i :=
    match Bin.comm (e_bin i) with Some _ ⇒ true | None ⇒ false end.

Normalisation


  Inductive discr {A} : Type :=
  | Is_op : A → discr
  | Is_unit : idx → discr
  | Is_nothing : discr .

  Inductive m {A} {B} :=
  | left : A → m
  | right : B → m.

  Definition comp A B (merge : B → B → B) (l : B) (l' : @m A B) : @m A B :=
    match l' with
      | left _ ⇒ right l
      | right l' ⇒ right (merge l l')
    end.

auxiliary functions, to clean up sums

  Section sums.
    Variable i : idx.
    Variable is_unit : idx → bool.

    Definition sum' (u: mset T): T :=
      match u with
        | nil (u,xH) ⇒ u
        | _ ⇒ sum i u
      end.

    Definition is_sum (u: T) : @discr (mset T) :=
    match u with
      | sum j l ⇒ if eq_idx_bool j i then Is_op l else Is_nothing
      | unit j ⇒ if is_unit j then Is_unit j else Is_nothing
      | u ⇒ Is_nothing
    end.

    Definition copy_mset n (l: mset T): mset T :=
      match n with
        | xH ⇒ l
        | _ ⇒ nelist_map (fun vm ⇒ let '(v,m):=vm in (v,Pmult n m)) l
      end.

    Definition return_sum u n :=
      match is_sum u with
        | Is_nothing ⇒ right (nil (u,n))
        | Is_op l' ⇒ right (copy_mset n l')
        | Is_unit j ⇒ left j
      end.

    Definition add_to_sum u n (l : @m idx (mset T)) :=
      match is_sum u with
        | Is_nothing ⇒ comp (merge_msets compare) (nil (u,n)) l
        | Is_op l' ⇒ comp (merge_msets compare) (copy_mset n l') l
        | Is_unit _ ⇒ l
    end.

    Definition norm_msets_ norm (l: mset T) :=
    fold_map'
    (fun un ⇒ let '(u,n) := un in return_sum (norm u) n)
    (fun un l ⇒ let '(u,n) := un in add_to_sum (norm u) n l) l.

  End sums.

similar functions for products

  Section prds.

    Variable i : idx.
    Variable is_unit : idx → bool.
    Definition prd' (u: nelist T): T :=
    match u with
      | nil u ⇒ u
      | _ ⇒ prd i u
    end.

    Definition is_prd (u: T) : @discr (nelist T) :=
    match u with
      | prd j l ⇒ if eq_idx_bool j i then Is_op l else Is_nothing
      | unit j ⇒ if is_unit j then Is_unit j else Is_nothing
      | u ⇒ Is_nothing
    end.


    Definition return_prd u :=
      match is_prd u with
        | Is_nothing ⇒ right (nil (u))
        | Is_op l' ⇒ right (l')
        | Is_unit j ⇒ left j
      end.

    Definition add_to_prd u (l : @m idx (nelist T)) :=
      match is_prd u with
        | Is_nothing ⇒ comp (@appne T) (nil (u)) l
        | Is_op l' ⇒ comp (@appne T) (l') l
        | Is_unit _ ⇒ l
      end.

    Definition norm_lists_ norm (l : nelist T) :=
    fold_map'
    (fun u ⇒ return_prd (norm u))
    (fun u l ⇒ add_to_prd (norm u) l) l.

  End prds.

  Definition run_list x := match x with
                        | left n ⇒ nil (unit n)
                        | right l ⇒ l
                      end.

  Definition norm_lists norm i l :=
    let is_unit := is_unit_of i in
      run_list (norm_lists_ i is_unit norm l).

  Definition run_msets x := match x with
                        | left n ⇒ nil (unit n, xH)
                        | right l ⇒ l
                      end.

  Definition norm_msets norm i l :=
    let is_unit := is_unit_of i in
      run_msets (norm_msets_ i is_unit norm l).

  Fixpoint norm u {struct u}:=
    match u with
      | sum i l ⇒ if is_commutative i then sum' i (norm_msets norm i l) else u
      | prd i l ⇒ prd' i (norm_lists norm i l)
      | sym i l ⇒ sym i (vnorm l)
      | unit i ⇒ unit i
    end
  with vnorm i (l: vT i): vT i :=
    match l with
      | vnil ⇒ vnil
      | vcons _ u l ⇒ vcons (norm u) (vnorm l)
    end.

Correctness


  Lemma is_unit_of_Unit : ∀ i j : idx,
   is_unit_of i j = true → Unit R (Bin.value (e_bin i)) (eval (unit j)).
  Proof.
    intros. unfold is_unit_of in H.
    rewrite existsb_exists in H.
    destruct H as [x [H H']].
    revert H' ; case (eq_idx_spec); [intros H' _ ; subst| intros _ H'; discriminate].
    simpl. destruct x. simpl. auto.
  Qed.

  Instance Binvalue_Commutative i (H : is_commutative i = true) : Commutative R (@Bin.value _ _ (e_bin i) ).
  Proof.
    unfold is_commutative in H.
    destruct (Bin.comm (e_bin i)); auto.
    discriminate.
  Qed.

  Instance Binvalue_Associative i :Associative R (@Bin.value _ _ (e_bin i) ).
  Proof.
    destruct ((e_bin i)); auto.
  Qed.

  Instance Binvalue_Proper i : Proper (R ==> R ==> R) (@Bin.value _ _ (e_bin i) ).
  Proof.
    destruct ((e_bin i)); auto.
  Qed.
  Hint Resolve Binvalue_Proper Binvalue_Associative Binvalue_Commutative.

auxiliary lemmas about sums

  Hint Resolve is_unit_of_Unit.
  Section sum_correctness.
    Variable i : idx.
    Variable is_unit : idx → bool.
    Hypothesis is_unit_sum_Unit : ∀ j, is_unit j = true→ @Unit X R (Bin.value (e_bin i)) (eval (unit j)).

    Inductive is_sum_spec_ind : T → @discr (mset T) → Prop :=
    | is_sum_spec_op : ∀ j l, j = i → is_sum_spec_ind (sum j l) (Is_op l)
    | is_sum_spec_unit : ∀ j, is_unit j = true → is_sum_spec_ind (unit j) (Is_unit j)
    | is_sum_spec_nothing : ∀ u, is_sum_spec_ind u (Is_nothing).

    Lemma is_sum_spec u : is_sum_spec_ind u (is_sum i is_unit u).
    Proof.
      unfold is_sum; case u; intros; try constructor.
      case_eq (eq_idx_bool p i); intros; subst; try constructor; auto.
      revert H. case eq_idx_spec; try discriminate. auto.
      case_eq (is_unit p); intros; try constructor. auto.
    Qed.

    Instance assoc : @Associative X R (Bin.value (e_bin i)).
    Proof.
      destruct (e_bin i). simpl. assumption.
    Qed.
    Instance proper : Proper (R ==> R ==> R)(Bin.value (e_bin i)).
    Proof.
      destruct (e_bin i). simpl. assumption.
    Qed.
    Hypothesis comm : @Commutative X R (Bin.value (e_bin i)).

    Lemma sum'_sum : ∀ (l: mset T), eval (sum' i l) ==eval (sum i l) .
    Proof.
      intros [[a n] | [a n] l]; destruct n; simpl; reflexivity.
    Qed.

    Lemma eval_sum_nil x:
      eval (sum i (nil (x,xH))) == (eval x).
    Proof. rewrite <- sum'_sum. reflexivity. Qed.

    Lemma eval_sum_cons : ∀ n a (l: mset T),
      (eval (sum i ((a,n)::l))) == (@Bin.value _ _ (e_bin i) (@copy _ (@Bin.value _ _ (e_bin i)) n (eval a)) (eval (sum i l))).
    Proof.
      intros n a [[? ? ]|[b m] l]; simpl; reflexivity.
    Qed.

    Inductive compat_sum_unit : @m idx (mset T) → Prop :=
    | csu_left : ∀ x, is_unit x = true→ compat_sum_unit (left x)
    | csu_right : ∀ m, compat_sum_unit (right m)
    .

    Lemma compat_sum_unit_return x n : compat_sum_unit (return_sum i is_unit x n).
    Proof.
      unfold return_sum.
      case is_sum_spec; intros; try constructor; auto.
    Qed.

    Lemma compat_sum_unit_add : ∀ x n h,
      compat_sum_unit h
      →
     compat_sum_unit
     (add_to_sum i (is_unit_of i) x n
       h).
    Proof.
      unfold add_to_sum;intros; inversion H;
        case_eq (is_sum i (is_unit_of i) x);
        intros; simpl; try constructor || eauto. apply H0.
    Qed.

    Hint Extern 5 (copy (?n + ?m) (eval ?a) == Bin.value (copy ?n (eval ?a)) (copy ?m (eval ?a))) ⇒ apply copy_plus.
    Hint Extern 5 (?x == ?x) ⇒ reflexivity.
    Hint Extern 5 ( Bin.value ?x ?y == Bin.value ?y ?x) ⇒ apply Bin.comm.

    Lemma eval_merge_bin : ∀ (h k: mset T),
      eval (sum i (merge_msets compare h k)) == @Bin.value _ _ (e_bin i) (eval (sum i h)) (eval (sum i k)).
    Proof.
      induction h as [[a n]|[a n] h IHh]; intro k.
      simpl.
      induction k as [[b m]|[b m] k IHk]; simpl.
      destruct (tcompare_weak_spec a b) as [a|a b|a b]; simpl; auto. apply copy_plus; auto.

      destruct (tcompare_weak_spec a b) as [a|a b|a b]; simpl; auto.
      rewrite copy_plus,law_assoc; auto.
      rewrite IHk; clear IHk. rewrite 2 law_assoc. apply proper. apply law_comm. reflexivity.

      induction k as [[b m]|[b m] k IHk]; simpl; simpl in IHh.
      destruct (tcompare_weak_spec a b) as [a|a b|a b]; simpl.
      rewrite (law_comm _ (copy m (eval a))), law_assoc, <- copy_plus, Pplus_comm; auto.
      rewrite <- law_assoc, IHh. reflexivity.
      rewrite law_comm. reflexivity.

      simpl in IHk.
      destruct (tcompare_weak_spec a b) as [a|a b|a b]; simpl.
      rewrite IHh; clear IHh. rewrite 2 law_assoc. rewrite (law_comm _ (copy m (eval a))). rewrite law_assoc, <- copy_plus, Pplus_comm; auto.
      rewrite IHh; clear IHh. simpl. rewrite law_assoc. reflexivity.
      rewrite 2 (law_comm (copy m (eval b))). rewrite law_assoc. apply proper; [ | reflexivity].
      rewrite <- IHk. reflexivity.
    Qed.


    Lemma copy_mset' n (l: mset T): copy_mset n l = nelist_map (fun vm ⇒ let '(v,m):=vm in (v,Pmult n m)) l.
    Proof.
      unfold copy_mset. destruct n; try reflexivity.

      simpl. induction l as [|[a l] IHl]; simpl; try congruence. destruct a. reflexivity.
    Qed.


    Lemma copy_mset_succ n (l: mset T): eval (sum i (copy_mset (Pos.succ n) l)) == @Bin.value _ _ (e_bin i) (eval (sum i l)) (eval (sum i (copy_mset n l))).
    Proof.
      rewrite 2 copy_mset'.

      induction l as [[a m]|[a m] l IHl].
      simpl eval. rewrite <- copy_plus; auto. rewrite Pmult_Sn_m. reflexivity.

      simpl nelist_map. rewrite ! eval_sum_cons. rewrite IHl. clear IHl.
      rewrite Pmult_Sn_m. rewrite copy_plus; auto. rewrite <- !law_assoc.
      apply Binvalue_Proper; try reflexivity.
      rewrite law_comm . rewrite <- !law_assoc. apply proper; try reflexivity.
      apply law_comm.
    Qed.

    Lemma copy_mset_copy : ∀ n (m : mset T), eval (sum i (copy_mset n m)) == @copy _ (@Bin.value _ _ (e_bin i)) n (eval (sum i m)).
    Proof.
      induction n using Pind; intros.

      unfold copy_mset. rewrite copy_xH. reflexivity.
      rewrite copy_mset_succ. rewrite copy_Psucc. rewrite IHn. reflexivity.
    Qed.

    Instance compat_sum_unit_Unit : ∀ p, compat_sum_unit (left p) →
      @Unit X R (Bin.value (e_bin i)) (eval (unit p)).
    Proof.
      intros.
      inversion H. subst. auto.
    Qed.

    Lemma copy_n_unit : ∀ j n, is_unit j = true →
      eval (unit j) == @copy _ (Bin.value (e_bin i)) n (eval (unit j)).
    Proof.
      intros.
      induction n using Prect.
      rewrite copy_xH. reflexivity.
      rewrite copy_Psucc. rewrite <- IHn. apply is_unit_sum_Unit in H. rewrite law_neutral_left. reflexivity.
    Qed.


    Lemma z0 l r (H : compat_sum_unit r):
      eval (sum i (run_msets (comp (merge_msets compare) l r))) == eval (sum i ((merge_msets compare) (l) (run_msets r))).
    Proof.
      unfold comp. unfold run_msets.
      case_eq r; intros; subst.
      rewrite eval_merge_bin; auto.
      rewrite eval_sum_nil.
      apply compat_sum_unit_Unit in H. rewrite law_neutral_right. reflexivity.
      reflexivity.
    Qed.

    Lemma z1 : ∀ n x,
      eval (sum i (run_msets (return_sum i (is_unit) x n )))
      == @copy _ (@Bin.value _ _ (e_bin i)) n (eval x).
    Proof.
      intros. unfold return_sum. unfold run_msets.
      case (is_sum_spec); intros; subst.
      rewrite copy_mset_copy.
      reflexivity.

      rewrite eval_sum_nil. apply copy_n_unit. auto.
      reflexivity.
    Qed.
    Lemma z2 : ∀ u n x, compat_sum_unit x →
      eval (sum i ( run_msets
        (add_to_sum i (is_unit) u n x)))
      ==
      @Bin.value _ _ (e_bin i) (@copy _ (@Bin.value _ _ (e_bin i)) n (eval u)) (eval (sum i (run_msets x))).
    Proof.
      intros u n x Hix .
      unfold add_to_sum.
      case is_sum_spec; intros; subst.

      rewrite z0 by auto. rewrite eval_merge_bin. rewrite copy_mset_copy. reflexivity.
      rewrite <- copy_n_unit by assumption.
      apply is_unit_sum_Unit in H.
      rewrite law_neutral_left. reflexivity.


      rewrite z0 by auto. rewrite eval_merge_bin. reflexivity.
    Qed.
  End sum_correctness.
  Lemma eval_norm_msets i norm
    (Comm : Commutative R (Bin.value (e_bin i)))
    (Hnorm: ∀ u, eval (norm u) == eval u) : ∀ h, eval (sum i (norm_msets norm i h)) == eval (sum i h).
  Proof.
    unfold norm_msets.
    assert (H :
      ∀ h : mset T,
        eval (sum i (run_msets (norm_msets_ i (is_unit_of i) norm h))) == eval (sum i h) ∧ compat_sum_unit (is_unit_of i) (norm_msets_ i (is_unit_of i) norm h)).

    induction h as [[a n] | [a n] h [IHh IHh']]; simpl norm_msets_; split.
    rewrite z1 by auto. rewrite Hnorm . reflexivity. auto.
    apply compat_sum_unit_return.

    rewrite z2 by auto. rewrite IHh.
    rewrite eval_sum_cons. rewrite Hnorm. reflexivity. apply compat_sum_unit_add, IHh'.

    apply H.
  Defined.

auxiliary lemmas about products

  Section prd_correctness.
    Variable i : idx.
    Variable is_unit : idx → bool.
    Hypothesis is_unit_prd_Unit : ∀ j, is_unit j = true→ @Unit X R (Bin.value (e_bin i)) (eval (unit j)).

    Inductive is_prd_spec_ind : T → @discr (nelist T) → Prop :=
    | is_prd_spec_op :
      ∀ j l, j = i → is_prd_spec_ind (prd j l) (Is_op l)
    | is_prd_spec_unit :
      ∀ j, is_unit j = true → is_prd_spec_ind (unit j) (Is_unit j)
    | is_prd_spec_nothing :
      ∀ u, is_prd_spec_ind u (Is_nothing).

    Lemma is_prd_spec u : is_prd_spec_ind u (is_prd i is_unit u).
    Proof.
      unfold is_prd; case u; intros; try constructor.
      case (eq_idx_spec); intros; subst; try constructor; auto.
      case_eq (is_unit p); intros; try constructor; auto.
    Qed.

    Lemma prd'_prd : ∀ (l: nelist T), eval (prd' i l) == eval (prd i l).
    Proof.
      intros [?|? [|? ?]]; simpl; reflexivity.
    Qed.


    Lemma eval_prd_nil x: eval (prd i (nil x)) == eval x.
    Proof.
      rewrite <- prd'_prd. simpl. reflexivity.
    Qed.
    Lemma eval_prd_cons a : ∀ (l: nelist T), eval (prd i (a::l)) == @Bin.value _ _ (e_bin i) (eval a) (eval (prd i l)).
    Proof.
      intros [|b l]; simpl; reflexivity.
    Qed.
    Lemma eval_prd_app : ∀ (h k: nelist T), eval (prd i (h++k)) == @Bin.value _ _ (e_bin i) (eval (prd i h)) (eval (prd i k)).
    Proof.
      induction h; intro k. simpl; try reflexivity.
      simpl appne. rewrite 2 eval_prd_cons, IHh, law_assoc. reflexivity.
    Qed.

    Inductive compat_prd_unit : @m idx (nelist T) → Prop :=
    | cpu_left : ∀ x, is_unit x = true → compat_prd_unit (left x)
    | cpu_right : ∀ m, compat_prd_unit (right m)
    .

    Lemma compat_prd_unit_return x: compat_prd_unit (return_prd i is_unit x).
    Proof.
      unfold return_prd.
      case (is_prd_spec); intros; try constructor; auto.
    Qed.

    Lemma compat_prd_unit_add : ∀ x h,
      compat_prd_unit h
      →
      compat_prd_unit
      (add_to_prd i is_unit x
        h).
    Proof.
      intros.
      unfold add_to_prd.
      unfold comp.
      case (is_prd_spec); intros; try constructor; auto.
      unfold comp; case h; try constructor.
      unfold comp; case h; try constructor.
    Qed.


    Instance compat_prd_Unit : ∀ p, compat_prd_unit (left p) →
      @Unit X R (Bin.value (e_bin i)) (eval (unit p)).
    Proof.
      intros.
      inversion H; subst. apply is_unit_prd_Unit. assumption.
    Qed.

    Lemma z0' : ∀ l (r: @m idx (nelist T)), compat_prd_unit r →
      eval (prd i (run_list (comp (@appne T) l r))) == eval (prd i ((appne (l) (run_list r)))).
    Proof.
      intros.
      unfold comp. unfold run_list. case_eq r; intros; auto; subst.
      rewrite eval_prd_app.
      rewrite eval_prd_nil.
      apply compat_prd_Unit in H. rewrite law_neutral_right. reflexivity.
      reflexivity.
    Qed.

    Lemma z1' a : eval (prd i (run_list (return_prd i is_unit a))) == eval (prd i (nil a)).
    Proof.
      intros. unfold return_prd. unfold run_list.
      case (is_prd_spec); intros; subst; reflexivity.
    Qed.
    Lemma z2' : ∀ u x, compat_prd_unit x →
      eval (prd i ( run_list
        (add_to_prd i is_unit u x))) == @Bin.value _ _ (e_bin i) (eval u) (eval (prd i (run_list x))).
    Proof.
      intros u x Hix.
      unfold add_to_prd.
      case (is_prd_spec); intros; subst.
      rewrite z0' by auto. rewrite eval_prd_app. reflexivity.
      apply is_unit_prd_Unit in H. rewrite law_neutral_left. reflexivity.
      rewrite z0' by auto. rewrite eval_prd_app. reflexivity.
    Qed.

  End prd_correctness.

  Lemma eval_norm_lists i (Hnorm: ∀ u, eval (norm u) == eval u) : ∀ h, eval (prd i (norm_lists norm i h)) == eval (prd i h).
  Proof.
    unfold norm_lists.
    assert (H : ∀ h : nelist T,
      eval (prd i (run_list (norm_lists_ i (is_unit_of i) norm h))) ==
      eval (prd i h)
      ∧ compat_prd_unit (is_unit_of i) (norm_lists_ i (is_unit_of i) norm h)).


      induction h as [a | a h [IHh IHh']]; simpl norm_lists_; split.
      rewrite z1'. simpl. apply Hnorm.

      apply compat_prd_unit_return.

      rewrite z2'. rewrite IHh. rewrite eval_prd_cons. rewrite Hnorm. reflexivity. apply is_unit_of_Unit.
      auto.

      apply compat_prd_unit_add. auto.
      apply H.
    Defined.

correctness of the normalisation function

  Theorem eval_norm: ∀ u, eval (norm u) == eval u
    with eval_norm_aux: ∀ i (l: vT i) (f: Sym.type_of i),
      Proper (@Sym.rel_of X R i) f → eval_aux (vnorm l) f == eval_aux l f.
  Proof.
    induction u as [ p m | p l | ? | ?]; simpl norm.
    case_eq (is_commutative p); intros.
    rewrite sum'_sum.
    apply eval_norm_msets; auto.
    reflexivity.

    rewrite prd'_prd.
    apply eval_norm_lists; auto.

    apply eval_norm_aux, Sym.morph.

    reflexivity.

    induction l; simpl; intros f Hf. reflexivity.
    rewrite eval_norm. apply IHl, Hf; reflexivity.
  Qed.

corollaries, for goal normalisation or decision

  Lemma normalise : ∀ (u v: T), eval (norm u) == eval (norm v) → eval u == eval v.
  Proof. intros u v. rewrite 2 eval_norm. trivial. Qed.

  Lemma compare_reflect_eq: ∀ u v, compare u v = Eq → eval u == eval v.
  Proof. intros u v. case (tcompare_weak_spec u v); intros; try congruence. reflexivity. Qed.

  Lemma decide: ∀ (u v: T), compare (norm u) (norm v) = Eq → eval u == eval v.
  Proof. intros u v H. apply normalise. apply compare_reflect_eq. apply H. Qed.

  Lemma lift_normalise {S} {H : AAC_lift S R}:
    ∀ (u v: T), (let x := norm u in let y := norm v in
      S (eval x) (eval y)) → S (eval u) (eval v).
  Proof. destruct H. intros u v; simpl; rewrite 2 eval_norm. trivial. Qed.

End s.
End Internal.

Local Ltac internal_normalize :=
  let x := fresh in let y := fresh in
  intro x; intro y; vm_compute in x; vm_compute in y; unfold x; unfold y;
  compute [Internal.eval Utils.fold_map Internal.copy Prect]; simpl.

Lemmas for performing transitivity steps

given an instance of AAC_lift

Section t.
  Context `{AAC_lift}.

  Lemma lift_transitivity_left (y x z : X): E x y → R y z → R x z.
  Proof. destruct H as [Hequiv Hproper]; intros G;rewrite G. trivial. Qed.

  Lemma lift_transitivity_right (y x z : X): E y z → R x y → R x z.
  Proof. destruct H as [Hequiv Hproper]; intros G. rewrite G. trivial. Qed.

  Lemma lift_reflexivity {HR :Reflexive R}: ∀ x y, E x y → R x y.
  Proof. destruct H. intros ? ? G. rewrite G. reflexivity. Qed.

End t.

Declare ML Module "aac_plugin".