theory Lambda

imports "../Parser"

begin

atom_decl name

nominal_datatype lam =

  Var "name"

| App "lam" "lam"

| Lam x::"name" l::"lam"  bind x in l

lemmas supp_fn' = lam.fv[simplified lam.supp]

section {* Strong Induction Principles*}

(* 

  Old way of establishing strong induction

  principles by chosing a fresh name.

*)

lemma

  fixes c::"'a::fs"

  assumes a1: "\<And>name c. P c (Var name)"

  and     a2: "\<And>lam1 lam2 c. \<lbrakk>\<And>d. P d lam1; \<And>d. P d lam2\<rbrakk> \<Longrightarrow> P c (App lam1 lam2)"

  and     a3: "\<And>name lam c. \<lbrakk>atom name \<sharp> c; \<And>d. P d lam\<rbrakk> \<Longrightarrow> P c (Lam name lam)"

  shows "P c lam"

proof -

  have "\<And>p. P c (p \<bullet> lam)"

    apply(induct lam arbitrary: c rule: lam.induct)

    apply(rule a1)

    apply(rule a2)

    apply(assumption)

    apply(assumption)

    apply(subgoal_tac "\<exists>new::name. (atom new) \<sharp> (c, Lam (p \<bullet> name) (p \<bullet> lam))")

    defer

    apply(simp add: fresh_def)

    apply(rule_tac X="supp (c, Lam (p \<bullet> name) (p \<bullet> lam))" in obtain_at_base)

    apply(simp add: supp_Pair finite_supp)

    apply(blast)

    apply(erule exE)

    apply(rule_tac t="p \<bullet> Lam name lam" and 

                   s="(((p \<bullet> name) \<leftrightarrow> new) + p) \<bullet> Lam name lam" in subst)

    apply(simp del: lam.perm)

    apply(subst lam.perm)

    apply(subst (2) lam.perm)

    apply(rule flip_fresh_fresh)

    apply(simp add: fresh_def)

    apply(simp only: supp_fn')

    apply(simp)

    apply(simp add: fresh_Pair)

    apply(simp)

    apply(rule a3)

    apply(simp add: fresh_Pair)

    apply(drule_tac x="((p \<bullet> name) \<leftrightarrow> new) + p" in meta_spec)

    apply(simp)

    done

  then have "P c (0 \<bullet> lam)" by blast

  then show "P c lam" by simp

qed

(* 

  New way of establishing strong induction

  principles by using a appropriate permutation.

*)

lemma

  fixes c::"'a::fs"

  assumes a1: "\<And>name c. P c (Var name)"

  and     a2: "\<And>lam1 lam2 c. \<lbrakk>\<And>d. P d lam1; \<And>d. P d lam2\<rbrakk> \<Longrightarrow> P c (App lam1 lam2)"

  and     a3: "\<And>name lam c. \<lbrakk>atom name \<sharp> c; \<And>d. P d lam\<rbrakk> \<Longrightarrow> P c (Lam name lam)"

  shows "P c lam"

proof -

  have "\<And>p. P c (p \<bullet> lam)"

    apply(induct lam arbitrary: c rule: lam.induct)

    apply(rule a1)

    apply(rule a2)

    apply(assumption)

    apply(assumption)

    apply(subgoal_tac "\<exists>q. (q \<bullet> {p \<bullet> atom name}) \<sharp>* c \<and> supp (p \<bullet> Lam name lam) \<sharp>* q")

    apply(erule exE)

    apply(rule_tac t="p \<bullet> Lam name lam" and 

                   s="q \<bullet> p \<bullet> Lam name lam" in subst)

    defer

    apply(rule a3)

    apply(simp add: eqvts fresh_star_def)

    apply(drule_tac x="q + p" in meta_spec)

    apply(simp)

    apply(rule at_set_avoiding2)

    apply(simp add: finite_supp)

    apply(simp add: finite_supp)

    apply(simp add: finite_supp)

    apply(simp add: fresh_star_def fresh_def supp_fn')

    apply(rule supp_perm_eq)

    apply(simp)

    done

  then have "P c (0 \<bullet> lam)" by blast

  then show "P c lam" by simp

qed

section {* size function *}

lemma size_eqvt_raw:

  fixes t::"lam_raw"

  shows "size (pi \<bullet> t)  = size t"

  apply (induct rule: lam_raw.inducts)

  apply simp_all

  done

instantiation lam :: size 

begin

quotient_definition

  "size_lam :: lam \<Rightarrow> nat"

is

  "size :: lam_raw \<Rightarrow> nat"

lemma size_rsp:

  "alpha_lam_raw x y \<Longrightarrow> size x = size y"

  apply (induct rule: alpha_lam_raw.inducts)

  apply (simp_all only: lam_raw.size)

  apply (simp_all only: alphas)

  apply clarify

  apply (simp_all only: size_eqvt_raw)

  done

lemma [quot_respect]:

  "(alpha_lam_raw ===> op =) size size"

  by (simp_all add: size_rsp)

lemma [quot_preserve]:

  "(rep_lam ---> id) size = size"

  by (simp_all add: size_lam_def)

instance

  by default

end

lemmas size_lam[simp] = 

  lam_raw.size(4)[quot_lifted]

  lam_raw.size(5)[quot_lifted]

  lam_raw.size(6)[quot_lifted]

(* is this needed? *)

lemma [measure_function]: 

  "is_measure (size::lam\<Rightarrow>nat)" 

  by (rule is_measure_trivial)

section {* Matching *}

definition

  MATCH :: "('c::pt \<Rightarrow> (bool * 'a::pt * 'b::pt)) \<Rightarrow> 'b \<Rightarrow> 'a \<Rightarrow> 'b"

where

  "MATCH M d x \<equiv> if (\<exists>!r. \<exists>q. M q = (True, x, r)) then (THE r. \<exists>q. M q = (True, x, r)) else d"

(*

lemma MATCH_eqvt:

  shows "p \<bullet> (MATCH M d x) = MATCH (p \<bullet> M) (p \<bullet> d) (p \<bullet> x)"

unfolding MATCH_def

apply(perm_simp the_eqvt)

apply (tactic {* Nominal_Permeq.eqvt_tac @{context} 1 *})

apply(simp)

thm eqvts_raw 

apply(subst if_eqvt)

apply(subst ex1_eqvt)

apply(subst permute_fun_def)

apply(subst ex_eqvt)

apply(subst permute_fun_def)

apply(subst eq_eqvt)

apply(subst permute_fun_app_eq[where f="M"])

apply(simp only: permute_minus_cancel)

apply(subst permute_prod.simps)

apply(subst permute_prod.simps)

apply(simp only: permute_minus_cancel)

apply(simp only: permute_bool_def)

apply(simp)

apply(subst ex1_eqvt)

apply(subst permute_fun_def)

apply(subst ex_eqvt)

apply(subst permute_fun_def)

apply(subst eq_eqvt)

apply(simp only: eqvts)

apply(simp)

apply(subgoal_tac "(p \<bullet> (\<exists>!r. \<exists>q. M q = (True, x, r))) = (\<exists>!r. \<exists>q. (p \<bullet> M) q = (True, p \<bullet> x, r))")

apply(drule sym)

apply(simp)

apply(rule impI)

apply(simp add: perm_bool)

apply(rule trans)

apply(rule pt_the_eqvt[OF pta at])

apply(assumption)

apply(simp add: pt_ex_eqvt[OF pt at])

apply(simp add: pt_eq_eqvt[OF ptb at])

apply(rule cheat)

apply(rule trans)

apply(rule pt_ex1_eqvt)

apply(rule pta)

apply(rule at)

apply(simp add: pt_ex_eqvt[OF pt at])

apply(simp add: pt_eq_eqvt[OF ptb at])

apply(subst pt_pi_rev[OF pta at])

apply(subst pt_fun_app_eq[OF pt at])

apply(subst pt_pi_rev[OF pt at])

apply(simp)

done

lemma MATCH_cng:

  assumes a: "M1 = M2" "d1 = d2"

  shows "MATCH M1 d1 x = MATCH M2 d2 x"

using a by simp

lemma MATCH_eq:

  assumes a: "t = l x" "G x" "\<And>x'. t = l x' \<Longrightarrow> G x' \<Longrightarrow> r x' = r x"

  shows "MATCH (\<lambda>x. (G x, l x, r x)) d t = r x"

using a

unfolding MATCH_def

apply(subst if_P)

apply(rule_tac a="r x" in ex1I)

apply(rule_tac x="x" in exI)

apply(blast)

apply(erule exE)

apply(drule_tac x="q" in meta_spec)

apply(auto)[1]

apply(rule the_equality)

apply(blast)

apply(erule exE)

apply(drule_tac x="q" in meta_spec)

apply(auto)[1]

done

lemma MATCH_eq2:

  assumes a: "t = l x1 x2" "G x1 x2" "\<And>x1' x2'. t = l x1' x2' \<Longrightarrow> G x1' x2' \<Longrightarrow> r x1' x2' = r x1 x2"

  shows "MATCH (\<lambda>(x1,x2). (G x1 x2, l x1 x2, r x1 x2)) d t = r x1 x2"

sorry

lemma MATCH_neq:

  assumes a: "\<And>x. t = l x \<Longrightarrow> G x \<Longrightarrow> False"

  shows "MATCH (\<lambda>x. (G x, l x, r x)) d t = d"

using a

unfolding MATCH_def

apply(subst if_not_P)

apply(blast)

apply(rule refl)

done

lemma MATCH_neq2:

  assumes a: "\<And>x1 x2. t = l x1 x2 \<Longrightarrow> G x1 x2 \<Longrightarrow> False"

  shows "MATCH (\<lambda>(x1,x2). (G x1 x2, l x1 x2, r x1 x2)) d t = d"

using a

unfolding MATCH_def

apply(subst if_not_P)

apply(auto)

done

*)

end