theory Let

imports "../Nominal2" 

begin

atom_decl name

nominal_datatype trm =

  Var "name"

| App "trm" "trm"

| Lam x::"name" t::"trm"  bind  x in t

| Let as::"assn" t::"trm"   bind "bn as" in t

and assn =

  ANil

| ACons "name" "trm" "assn"

binder

  bn

where

  "bn ANil = []"

| "bn (ACons x t as) = (atom x) # (bn as)"

print_theorems

thm alpha_trm_raw_alpha_assn_raw_alpha_bn_raw.intros

thm bn_raw.simps

thm permute_bn_raw.simps

thm trm_assn.perm_bn_alpha

thm trm_assn.permute_bn

thm trm_assn.fv_defs

thm trm_assn.eq_iff 

thm trm_assn.bn_defs

thm trm_assn.bn_inducts

thm trm_assn.perm_simps

thm trm_assn.induct

thm trm_assn.inducts

thm trm_assn.distinct

thm trm_assn.supp

thm trm_assn.fresh

thm trm_assn.exhaust

thm trm_assn.strong_exhaust

thm trm_assn.perm_bn_simps

lemma alpha_bn_inducts_raw[consumes 1]:

  "\<lbrakk>alpha_bn_raw a b; P3 ANil_raw ANil_raw;

 \<And>trm_raw trm_rawa assn_raw assn_rawa name namea.

    \<lbrakk>alpha_trm_raw trm_raw trm_rawa; alpha_bn_raw assn_raw assn_rawa;

     P3 assn_raw assn_rawa\<rbrakk>

    \<Longrightarrow> P3 (ACons_raw name trm_raw assn_raw)

        (ACons_raw namea trm_rawa assn_rawa)\<rbrakk> \<Longrightarrow> P3 a b"

  by (erule alpha_trm_raw_alpha_assn_raw_alpha_bn_raw.inducts(3)[of _ _ "\<lambda>x y. True" _ "\<lambda>x y. True", simplified]) auto

lemmas alpha_bn_inducts[consumes 1] = alpha_bn_inducts_raw[quot_lifted]

lemma alpha_bn_refl: "alpha_bn x x"

  by (induct x rule: trm_assn.inducts(2))

     (rule TrueI, auto simp add: trm_assn.eq_iff)

lemma alpha_bn_sym: "alpha_bn x y \<Longrightarrow> alpha_bn y x"

  sorry

lemma alpha_bn_trans: "alpha_bn x y \<Longrightarrow> alpha_bn y z \<Longrightarrow> alpha_bn x z"

  sorry

lemma bn_inj[rule_format]:

  assumes a: "alpha_bn x y"

  shows "bn x = bn y \<longrightarrow> x = y"

  by (rule alpha_bn_inducts[OF a]) (simp_all add: trm_assn.bn_defs)

lemma bn_inj2:

  assumes a: "alpha_bn x y"

  shows "\<And>q r. (q \<bullet> bn x) = (r \<bullet> bn y) \<Longrightarrow> permute_bn q x = permute_bn r y"

using a

apply(induct rule: alpha_bn_inducts)

apply(simp add: trm_assn.perm_bn_simps)

apply(simp add: trm_assn.perm_bn_simps)

apply(simp add: trm_assn.bn_defs)

apply(simp add: atom_eqvt)

done

lemma Abs_lst_fcb2:

    and x y :: "'b :: fs"

  and perm1: "\<And>p. supp p \<sharp>* c \<Longrightarrow> p \<bullet> (f as x c) = f (p \<bullet> as) (p \<bullet> x) c"

  and perm2: "\<And>p. supp p \<sharp>* c \<Longrightarrow> p \<bullet> (f bs y c) = f (p \<bullet> bs) (p \<bullet> y) c"

  shows "f as x c = f bs y c"

proof -

  have "supp (as, x, c) supports (f as x c)"

    unfolding  supports_def fresh_def[symmetric]

  then have fin1: "finite (supp (f as x c))"

  have "supp (bs, y, c) supports (f bs y c)"

    unfolding  supports_def fresh_def[symmetric]

  then have fin2: "finite (supp (f bs y c))"

  obtain q::"perm" where 

    by (simp only: fr2 perm_supp_eq)

  then obtain r::perm where 

    qq1: "q \<bullet> x = r \<bullet> y" and 

    apply(drule_tac sym)

    apply(simp only: Abs_eq_iff2 alphas)

    apply(erule exE)

    apply(erule conjE)+

    apply(drule_tac x="p" in meta_spec)

    apply(simp add: set_eqvt)

    apply(blast)

    by (simp add: permute_bool_def)

    apply(simp add: fresh_star_eqvt set_eqvt)

    apply(subst (asm) perm1)

    using inc fresh1 fr1

    apply(auto simp add: fresh_star_def fresh_Pair)

    done

    apply(simp add: fresh_star_eqvt set_eqvt)

    apply(subst (asm) perm2[symmetric])

    using qq3 fresh2 fr1

    apply(auto simp add: set_eqvt fresh_star_def fresh_Pair)

    done

  have "f as x c = q \<bullet> (f as x c)"

    apply(rule perm_supp_eq[symmetric])

    apply(rule perm1)

    using inc fresh1 fr1 by (auto simp add: fresh_star_def)

  also have "\<dots> = r \<bullet> (f bs y c)"

    apply(rule perm2[symmetric])

    using qq3 fresh2 fr1 by (auto simp add: fresh_star_def)

  also have "... = f bs y c"

    apply(rule perm_supp_eq)

    using qq3 fr1 fcb2 by (auto simp add: fresh_star_def)

  finally show ?thesis by simp

qed

nominal_primrec

    height_trm :: "trm \<Rightarrow> nat"

where

  "height_trm (Var x) = 1"

| "height_trm (App l r) = max (height_trm l) (height_trm r)"

| "height_trm (Lam v b) = 1 + (height_trm b)"

  apply (rule, perm_simp, rule, rule TrueI)

  apply (auto)[4]

  apply (drule_tac x="assn" in meta_spec)

  apply (drule_tac x="trm" in meta_spec)

  apply (simp add: alpha_bn_refl)

  apply (simp_all add: pure_fresh fresh_star_def)[3]

  apply (simp_all add: eqvt_at_def)[2]

nominal_primrec

    subst  :: "name \<Rightarrow> trm \<Rightarrow> trm \<Rightarrow> trm"

where

  "subst s t (Var x) = (if (s = x) then t else (Var x))"

| "subst s t (App l r) = App (subst s t l) (subst s t r)"

| "atom v \<sharp> (s, t) \<Longrightarrow> subst s t (Lam v b) = Lam v (subst s t b)"

  apply (rule TrueI)

  apply (case_tac x)

  apply (auto simp add: fresh_star_def)[3]

  apply (drule_tac x="assn" in meta_spec)

  apply (simp add: Abs1_eq_iff alpha_bn_refl)

  apply auto

  apply (erule_tac c="(sa, ta)" in Abs_lst_fcb2)

  apply (erule alpha_bn_inducts)

lemma lets_bla:

  "x \<noteq> z \<Longrightarrow> y \<noteq> z \<Longrightarrow> x \<noteq> y \<Longrightarrow>(Let (ACons x (Var y) ANil) (Var x)) \<noteq> (Let (ACons x (Var z) ANil) (Var x))"

  by (simp add: trm_assn.eq_iff)

lemma lets_ok:

  "(Let (ACons x (Var y) ANil) (Var x)) = (Let (ACons y (Var y) ANil) (Var y))"

  apply (simp add: trm_assn.eq_iff Abs_eq_iff )

  apply (rule_tac x="(x \<leftrightarrow> y)" in exI)

  apply (simp_all add: alphas atom_eqvt supp_at_base fresh_star_def trm_assn.bn_defs trm_assn.supp)

  done

lemma lets_ok3:

  "x \<noteq> y \<Longrightarrow>

   (Let (ACons x (App (Var y) (Var x)) (ACons y (Var y) ANil)) (App (Var x) (Var y))) \<noteq>

   (Let (ACons y (App (Var x) (Var y)) (ACons x (Var x) ANil)) (App (Var x) (Var y)))"

  apply (simp add: trm_assn.eq_iff)

  done

lemma lets_not_ok1:

  "x \<noteq> y \<Longrightarrow>

   (Let (ACons x (Var x) (ACons y (Var y) ANil)) (App (Var x) (Var y))) \<noteq>

   (Let (ACons y (Var x) (ACons x (Var y) ANil)) (App (Var x) (Var y)))"

  apply (simp add: alphas trm_assn.eq_iff trm_assn.supp fresh_star_def atom_eqvt Abs_eq_iff trm_assn.bn_defs)

  done

lemma lets_nok:

  "x \<noteq> y \<Longrightarrow> x \<noteq> z \<Longrightarrow> z \<noteq> y \<Longrightarrow>

   (Let (ACons x (App (Var z) (Var z)) (ACons y (Var z) ANil)) (App (Var x) (Var y))) \<noteq>

   (Let (ACons y (Var z) (ACons x (App (Var z) (Var z)) ANil)) (App (Var x) (Var y)))"

  apply (simp add: alphas trm_assn.eq_iff fresh_star_def trm_assn.bn_defs Abs_eq_iff trm_assn.supp trm_assn.distinct)

  done

lemma

  fixes a b c :: name

  assumes x: "a \<noteq> c" and y: "b \<noteq> c"

  shows "\<exists>p.([atom a], Var c) \<approx>lst (op =) supp p ([atom b], Var c)"

  apply (rule_tac x="(a \<leftrightarrow> b)" in exI)

  apply (simp add: alphas trm_assn.supp supp_at_base x y fresh_star_def atom_eqvt)

  by (metis Rep_name_inverse atom_name_def flip_fresh_fresh fresh_atom fresh_perm x y)