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From iris.program_logic Require Export fancy_updates.
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From iris.program_logic Require Import wsat.
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From iris.base_logic Require Import big_op.
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From iris.prelude Require Export coPset.
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From iris.proofmode Require Import tactics classes.
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Import uPred.

Definition wp_pre `{irisG Λ Σ}
    (wp : coPset -c> expr Λ -c> (val Λ -c> iProp Σ) -c> iProp Σ) :
    coPset -c> expr Λ -c> (val Λ -c> iProp Σ) -c> iProp Σ := λ E e1 Φ, (
  (* value case *)
  ( v, to_val e1 = Some v  |={E}=> Φ v) 
  (* step case *)
  (to_val e1 = None   σ1,
     ownP_auth σ1 ={E,}=  reducible e1 σ1 
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       e2 σ2 efs,  prim_step e1 σ1 e2 σ2 efs ={,E}=
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       ownP_auth σ2  wp E e2 Φ 
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       [ list] ef  efs, wp  ef (λ _, True)))%I.
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Local Instance wp_pre_contractive `{irisG Λ Σ} : Contractive wp_pre.
Proof.
  rewrite /wp_pre=> n wp wp' Hwp E e1 Φ.
  apply or_ne, and_ne, forall_ne; auto=> σ1; apply wand_ne; auto.
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  apply fupd_ne, sep_ne, later_contractive; auto=> i ?.
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  apply forall_ne=> e2; apply forall_ne=> σ2; apply forall_ne=> efs.
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  apply wand_ne, fupd_ne, sep_ne, sep_ne; auto; first by apply Hwp.
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  apply big_opL_ne=> ? ef. by apply Hwp.
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Qed.
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Definition wp_def `{irisG Λ Σ} :
  coPset  expr Λ  (val Λ  iProp Σ)  iProp Σ := fixpoint wp_pre.
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Definition wp_aux : { x | x = @wp_def }. by eexists. Qed.
Definition wp := proj1_sig wp_aux.
Definition wp_eq : @wp = @wp_def := proj2_sig wp_aux.

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Arguments wp {_ _ _} _ _%E _.
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Instance: Params (@wp) 5.
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Notation "'WP' e @ E {{ Φ } }" := (wp E e%E Φ)
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  (at level 20, e, Φ at level 200,
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   format "'WP'  e  @  E  {{  Φ  } }") : uPred_scope.
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Notation "'WP' e {{ Φ } }" := (wp  e%E Φ)
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  (at level 20, e, Φ at level 200,
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   format "'WP'  e  {{  Φ  } }") : uPred_scope.
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Notation "'WP' e @ E {{ v , Q } }" := (wp E e%E (λ v, Q))
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  (at level 20, e, Q at level 200,
   format "'WP'  e  @  E  {{  v ,  Q  } }") : uPred_scope.
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Notation "'WP' e {{ v , Q } }" := (wp  e%E (λ v, Q))
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  (at level 20, e, Q at level 200,
   format "'WP'  e  {{  v ,  Q  } }") : uPred_scope.

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Section wp.
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Context `{irisG Λ Σ}.
Implicit Types P : iProp Σ.
Implicit Types Φ : val Λ  iProp Σ.
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Implicit Types v : val Λ.
Implicit Types e : expr Λ.
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Lemma wp_unfold E e Φ : WP e @ E {{ Φ }}  wp_pre wp E e Φ.
Proof. rewrite wp_eq. apply (fixpoint_unfold wp_pre). Qed.

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Global Instance wp_ne E e n :
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  Proper (pointwise_relation _ (dist n) ==> dist n) (@wp Λ Σ _ E e).
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Proof.
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  revert e. induction (lt_wf n) as [n _ IH]=> e Φ Ψ HΦ.
  rewrite !wp_unfold /wp_pre. apply or_ne, and_ne; auto; first solve_proper.
  apply forall_ne=> σ1.
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  apply wand_ne, fupd_ne, sep_ne, later_contractive; auto=> i ?.
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  apply forall_ne=> e2; apply forall_ne=> σ2; apply forall_ne=> ef.
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  apply wand_ne, fupd_ne, sep_ne, sep_ne; auto.
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  apply IH; [done|]=> v. eapply dist_le; eauto with omega.
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Qed.
Global Instance wp_proper E e :
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  Proper (pointwise_relation _ () ==> ()) (@wp Λ Σ _ E e).
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Proof.
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  by intros Φ Φ' ?; apply equiv_dist=>n; apply wp_ne=>v; apply equiv_dist.
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Qed.
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Lemma wp_value' E Φ v : Φ v  WP of_val v @ E {{ Φ }}.
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Proof.
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  iIntros "HΦ". rewrite wp_unfold /wp_pre.
  iLeft; iExists v; rewrite to_of_val; auto.
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Qed.
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Lemma wp_value_inv E Φ v : WP of_val v @ E {{ Φ }} ={E}= Φ v.
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Proof.
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  rewrite wp_unfold /wp_pre to_of_val. iIntros "[H|[% _]]"; [|done].
  by iDestruct "H" as (v') "[% ?]"; simplify_eq.
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Qed.
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Lemma wp_strong_mono E1 E2 e Φ Ψ :
  E1  E2  ( v, Φ v ={E2}= Ψ v)  WP e @ E1 {{ Φ }}  WP e @ E2 {{ Ψ }}.
Proof.
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  iIntros (?) "[HΦ H]". iLöb as "IH" forall (e). rewrite !wp_unfold /wp_pre.
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  iDestruct "H" as "[Hv|[% H]]"; [iLeft|iRight].
  { iDestruct "Hv" as (v) "[% Hv]". iExists v; iSplit; first done.
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    iApply ("HΦ" with "==>[-]"). by iApply (fupd_mask_mono E1 _). }
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  iSplit; [done|]; iIntros (σ1) "Hσ".
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  iUpd (fupd_intro_mask' E2 E1) as "Hclose"; first done.
  iUpd ("H" $! σ1 with "Hσ") as "[$ H]".
  iUpdIntro. iNext. iIntros (e2 σ2 efs Hstep).
  iUpd ("H" $! _ σ2 efs with "[#]") as "($ & H & $)"; auto.
  iUpd "Hclose" as "_". by iApply ("IH" with "HΦ").
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Qed.

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Lemma fupd_wp E e Φ : (|={E}=> WP e @ E {{ Φ }})  WP e @ E {{ Φ }}.
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Proof.
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  rewrite wp_unfold /wp_pre. iIntros "H". destruct (to_val e) as [v|] eqn:?.
  { iLeft. iExists v; iSplit; first done.
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    by iUpd "H" as "[H|[% ?]]"; [iDestruct "H" as (v') "[% ?]"|]; simplify_eq. }
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  iRight; iSplit; [done|]; iIntros (σ1) "Hσ1".
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  iUpd "H" as "[H|[% H]]"; last by iApply "H".
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  iDestruct "H" as (v') "[% ?]"; simplify_eq.
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Qed.
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Lemma wp_fupd E e Φ : WP e @ E {{ v, |={E}=> Φ v }}  WP e @ E {{ Φ }}.
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Proof. iIntros "H". iApply (wp_strong_mono E); try iFrame; auto. Qed.
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Lemma wp_atomic E1 E2 e Φ :
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  atomic e 
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  (|={E1,E2}=> WP e @ E2 {{ v, |={E2,E1}=> Φ v }})  WP e @ E1 {{ Φ }}.
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Proof.
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  iIntros (Hatomic) "H". destruct (to_val e) as [v|] eqn:He.
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  { apply of_to_val in He as <-. iApply wp_fupd. iApply wp_value'.
    iUpd "H". by iUpd (wp_value_inv with "H"). }
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  setoid_rewrite wp_unfold; rewrite /wp_pre. iRight; iSplit; auto.
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  iIntros (σ1) "Hσ". iUpd "H" as "[H|[_ H]]".
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  { iDestruct "H" as (v') "[% ?]"; simplify_eq. }
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  iUpd ("H" $! σ1 with "Hσ") as "[$ H]".
  iUpdIntro. iNext. iIntros (e2 σ2 efs Hstep).
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  destruct (Hatomic _ _ _ _ Hstep) as [v <-%of_to_val].
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  iUpd ("H" $! _ σ2 efs with "[#]") as "($ & H & $)"; auto.
  iUpd (wp_value_inv with "H") as "==> H". by iApply wp_value'.
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Qed.
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Lemma wp_frame_step_l E1 E2 e Φ R :
  to_val e = None  E2  E1 
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  (|={E1,E2}=> R)  WP e @ E2 {{ Φ }}  WP e @ E1 {{ v, R  Φ v }}.
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Proof.
  rewrite !wp_unfold /wp_pre. iIntros (??) "[HR [Hv|[_ H]]]".
  { iDestruct "Hv" as (v) "[% Hv]"; simplify_eq. }
  iRight; iSplit; [done|]. iIntros (σ1) "Hσ".
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  iUpd "HR". iUpd ("H" $! _ with "Hσ") as "[$ H]".
  iUpdIntro; iNext; iIntros (e2 σ2 efs Hstep).
  iUpd ("H" $! e2 σ2 efs with "[%]") as "($ & H & $)"; auto.
  iUpd "HR". iUpdIntro. iApply (wp_strong_mono E2 _ _ Φ); try iFrame; eauto.
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Qed.
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Lemma wp_bind K `{!LanguageCtx Λ K} E e Φ :
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  WP e @ E {{ v, WP K (of_val v) @ E {{ Φ }} }}  WP K e @ E {{ Φ }}.
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Proof.
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  iIntros "H". iLöb as "IH" forall (E e Φ). rewrite wp_unfold /wp_pre.
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  iDestruct "H" as "[Hv|[% H]]".
  { iDestruct "Hv" as (v) "[Hev Hv]"; iDestruct "Hev" as % <-%of_to_val.
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    by iApply fupd_wp. }
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  rewrite wp_unfold /wp_pre. iRight; iSplit; eauto using fill_not_val.
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  iIntros (σ1) "Hσ". iUpd ("H" $! _ with "Hσ") as "[% H]".
  iUpdIntro; iSplit.
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  { iPureIntro. unfold reducible in *. naive_solver eauto using fill_step. }
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  iNext; iIntros (e2 σ2 efs Hstep).
  destruct (fill_step_inv e σ1 e2 σ2 efs) as (e2'&->&?); auto.
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  iUpd ("H" $! e2' σ2 efs with "[%]") as "($ & H & $)"; auto.
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  by iApply "IH".
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Qed.

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(** * Derived rules *)
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Lemma wp_mono E e Φ Ψ : ( v, Φ v  Ψ v)  WP e @ E {{ Φ }}  WP e @ E {{ Ψ }}.
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Proof.
  iIntros (HΦ) "H"; iApply (wp_strong_mono E E); auto.
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  iFrame. iIntros (v) "?". by iApply HΦ.
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Qed.
Lemma wp_mask_mono E1 E2 e Φ : E1  E2  WP e @ E1 {{ Φ }}  WP e @ E2 {{ Φ }}.
Proof. iIntros (?) "H"; iApply (wp_strong_mono E1 E2); auto. iFrame; eauto. Qed.
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Global Instance wp_mono' E e :
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  Proper (pointwise_relation _ () ==> ()) (@wp Λ Σ _ E e).
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Proof. by intros Φ Φ' ?; apply wp_mono. Qed.
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Lemma wp_value E Φ e v : to_val e = Some v  Φ v  WP e @ E {{ Φ }}.
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Proof. intros; rewrite -(of_to_val e v) //; by apply wp_value'. Qed.
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Lemma wp_value_fupd' E Φ v : (|={E}=> Φ v)  WP of_val v @ E {{ Φ }}.
Proof. intros. by rewrite -wp_fupd -wp_value'. Qed.
Lemma wp_value_fupd E Φ e v :
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  to_val e = Some v  (|={E}=> Φ v)  WP e @ E {{ Φ }}.
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Proof. intros. rewrite -wp_fupd -wp_value //. Qed.
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Lemma wp_frame_l E e Φ R : R  WP e @ E {{ Φ }}  WP e @ E {{ v, R  Φ v }}.
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Proof. iIntros "[??]". iApply (wp_strong_mono E E _ Φ); try iFrame; eauto. Qed.
Lemma wp_frame_r E e Φ R : WP e @ E {{ Φ }}  R  WP e @ E {{ v, Φ v  R }}.
Proof. iIntros "[??]". iApply (wp_strong_mono E E _ Φ); try iFrame; eauto. Qed.

Lemma wp_frame_step_r E1 E2 e Φ R :
  to_val e = None  E2  E1 
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  WP e @ E2 {{ Φ }}  (|={E1,E2}=> R)  WP e @ E1 {{ v, Φ v  R }}.
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Proof.
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  rewrite [(WP _ @ _ {{ _ }}  _)%I]comm; setoid_rewrite (comm _ _ R).
  apply wp_frame_step_l.
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Qed.
Lemma wp_frame_step_l' E e Φ R :
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  to_val e = None   R  WP e @ E {{ Φ }}  WP e @ E {{ v, R  Φ v }}.
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Proof. iIntros (?) "[??]". iApply (wp_frame_step_l E E); try iFrame; eauto. Qed.
Lemma wp_frame_step_r' E e Φ R :
  to_val e = None  WP e @ E {{ Φ }}   R  WP e @ E {{ v, Φ v  R }}.
Proof. iIntros (?) "[??]". iApply (wp_frame_step_r E E); try iFrame; eauto. Qed.

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Lemma wp_wand_l E e Φ Ψ :
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  ( v, Φ v - Ψ v)  WP e @ E {{ Φ }}  WP e @ E {{ Ψ }}.
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Proof.
  iIntros "[H Hwp]". iApply (wp_strong_mono E); auto.
  iFrame "Hwp". iIntros (?) "?". by iApply "H".
Qed.
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Lemma wp_wand_r E e Φ Ψ :
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  WP e @ E {{ Φ }}  ( v, Φ v - Ψ v)  WP e @ E {{ Ψ }}.
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Proof. by rewrite comm wp_wand_l. Qed.
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End wp.
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(** Proofmode class instances *)
Section proofmode_classes.
  Context `{irisG Λ Σ}.
  Implicit Types P Q : iProp Σ.
  Implicit Types Φ : val Λ  iProp Σ.

  Global Instance frame_wp E e R Φ Ψ :
    ( v, Frame R (Φ v) (Ψ v))  Frame R (WP e @ E {{ Φ }}) (WP e @ E {{ Ψ }}).
  Proof. rewrite /Frame=> HR. rewrite wp_frame_l. apply wp_mono, HR. Qed.

  Global Instance is_except_last_wp E e Φ : IsExceptLast (WP e @ E {{ Φ }}).
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  Proof. by rewrite /IsExceptLast -{2}fupd_wp -except_last_fupd -fupd_intro. Qed.
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  Global Instance elim_upd_bupd_wp E e P Φ :
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    ElimUpd (|==> P) P (WP e @ E {{ Φ }}) (WP e @ E {{ Φ }}).
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  Proof. by rewrite /ElimUpd (bupd_fupd E) fupd_frame_r wand_elim_r fupd_wp. Qed.
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  Global Instance elim_upd_fupd_wp E e P Φ :
    ElimUpd (|={E}=> P) P (WP e @ E {{ Φ }}) (WP e @ E {{ Φ }}).
  Proof. by rewrite /ElimUpd fupd_frame_r wand_elim_r fupd_wp. Qed.
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  (* lower precedence, if possible, it should always pick elim_upd_fupd_wp *)
  Global Instance elim_upd_fupd_wp_atomic E1 E2 e P Φ :
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    atomic e 
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    ElimUpd (|={E1,E2}=> P) P
            (WP e @ E1 {{ Φ }}) (WP e @ E2 {{ v, |={E2,E1}=> Φ v }})%I | 100.
  Proof. intros. by rewrite /ElimUpd fupd_frame_r wand_elim_r wp_atomic. Qed.
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End proofmode_classes.