Theory Up (Isabelle2005: October 2005)

# Theory Up

Up to index of Isabelle/HOLCF

theory Up
imports Cfun Sum_Type Datatype
uses [Up.ML]
begin

    (*  Title:      HOLCF/Up.thy
        ID:         $Id: Up.thy,v 1.12 2005/09/22 17:06:06 huffman Exp $
        Author:     Franz Regensburger and Brian Huffman

    Lifting.
    *)

    header {* The type of lifted values *}

    theory Up
    imports Cfun Sum_Type Datatype
    begin

    defaultsort cpo

    subsection {* Definition of new type for lifting *}

    datatype 'a u = Ibottom | Iup 'a

    consts
      Ifup :: "('a -> 'b::pcpo) => 'a u => 'b"

    primrec
      "Ifup f Ibottom = ⊥"
      "Ifup f (Iup x) = f·x"

    subsection {* Ordering on type @{typ "'a u"} *}

    instance u :: (sq_ord) sq_ord ..

    defs (overloaded)
      less_up_def:
        "(op \<sqsubseteq>) ≡ (λx y. case x of Ibottom => True | Iup a =>
          (case y of Ibottom => False | Iup b => a \<sqsubseteq> b))"

    lemma minimal_up [iff]: "Ibottom \<sqsubseteq> z"
    by (simp add: less_up_def)

    lemma not_Iup_less [iff]: "¬ Iup x \<sqsubseteq> Ibottom"
    by (simp add: less_up_def)

    lemma Iup_less [iff]: "(Iup x \<sqsubseteq> Iup y) = (x \<sqsubseteq> y)"
    by (simp add: less_up_def)

    subsection {* Type @{typ "'a u"} is a partial order *}

    lemma refl_less_up: "(x::'a u) \<sqsubseteq> x"
    by (simp add: less_up_def split: u.split)

    lemma antisym_less_up: "[|(x::'a u) \<sqsubseteq> y; y \<sqsubseteq> x|] ==> x = y"
    apply (simp add: less_up_def split: u.split_asm)
    apply (erule (1) antisym_less)
    done

    lemma trans_less_up: "[|(x::'a u) \<sqsubseteq> y; y \<sqsubseteq> z|] ==> x \<sqsubseteq> z"
    apply (simp add: less_up_def split: u.split_asm)
    apply (erule (1) trans_less)
    done

    instance u :: (cpo) po
    by intro_classes
      (assumption | rule refl_less_up antisym_less_up trans_less_up)+

    subsection {* Type @{typ "'a u"} is a cpo *}

    lemma is_lub_Iup:
      "range S <<| x ==> range (λi. Iup (S i)) <<| Iup x"
    apply (rule is_lubI)
    apply (rule ub_rangeI)
    apply (subst Iup_less)
    apply (erule is_ub_lub)
    apply (case_tac u)
    apply (drule ub_rangeD)
    apply simp
    apply simp
    apply (erule is_lub_lub)
    apply (rule ub_rangeI)
    apply (drule_tac i=i in ub_rangeD)
    apply simp
    done

    text {* Now some lemmas about chains of @{typ "'a u"} elements *}

    lemma up_lemma1: "z ≠ Ibottom ==> Iup (THE a. Iup a = z) = z"
    by (case_tac z, simp_all)

    lemma up_lemma2:
      "[|chain Y; Y j ≠ Ibottom|] ==> Y (i + j) ≠ Ibottom"
    apply (erule contrapos_nn)
    apply (drule_tac x="j" and y="i + j" in chain_mono3)
    apply (rule le_add2)
    apply (case_tac "Y j")
    apply assumption
    apply simp
    done

    lemma up_lemma3:
      "[|chain Y; Y j ≠ Ibottom|] ==> Iup (THE a. Iup a = Y (i + j)) = Y (i + j)"
    by (rule up_lemma1 [OF up_lemma2])

    lemma up_lemma4:
      "[|chain Y; Y j ≠ Ibottom|] ==> chain (λi. THE a. Iup a = Y (i + j))"
    apply (rule chainI)
    apply (rule Iup_less [THEN iffD1])
    apply (subst up_lemma3, assumption+)+
    apply (simp add: chainE)
    done

    lemma up_lemma5:
      "[|chain Y; Y j ≠ Ibottom|] ==>
        (λi. Y (i + j)) = (λi. Iup (THE a. Iup a = Y (i + j)))"
    by (rule ext, rule up_lemma3 [symmetric])

    lemma up_lemma6:
      "[|chain Y; Y j ≠ Ibottom|]
          ==> range Y <<| Iup (\<Squnion>i. THE a. Iup a = Y(i + j))"
    apply (rule_tac j1 = j in is_lub_range_shift [THEN iffD1])
    apply assumption
    apply (subst up_lemma5, assumption+)
    apply (rule is_lub_Iup)
    apply (rule thelubE [OF _ refl])
    apply (erule (1) up_lemma4)
    done

    lemma up_chain_cases:
      "chain Y ==>
       (∃A. chain A ∧ lub (range Y) = Iup (lub (range A)) ∧
       (∃j. ∀i. Y (i + j) = Iup (A i))) ∨ (Y = (λi. Ibottom))"
    apply (rule disjCI)
    apply (simp add: expand_fun_eq)
    apply (erule exE, rename_tac j)
    apply (rule_tac x="λi. THE a. Iup a = Y (i + j)" in exI)
    apply (simp add: up_lemma4)
    apply (simp add: up_lemma6 [THEN thelubI])
    apply (rule_tac x=j in exI)
    apply (simp add: up_lemma3)
    done

    lemma cpo_up: "chain (Y::nat => 'a u) ==> ∃x. range Y <<| x"
    apply (frule up_chain_cases, safe)
    apply (rule_tac x="Iup (lub (range A))" in exI)
    apply (erule_tac j1="j" in is_lub_range_shift [THEN iffD1])
    apply (simp add: is_lub_Iup thelubE)
    apply (rule exI, rule lub_const)
    done

    instance u :: (cpo) cpo
    by intro_classes (rule cpo_up)

    subsection {* Type @{typ "'a u"} is pointed *}

    lemma least_up: "∃x::'a u. ∀y. x \<sqsubseteq> y"
    apply (rule_tac x = "Ibottom" in exI)
    apply (rule minimal_up [THEN allI])
    done

    instance u :: (cpo) pcpo
    by intro_classes (rule least_up)

    text {* for compatibility with old HOLCF-Version *}
    lemma inst_up_pcpo: "⊥ = Ibottom"
    by (rule minimal_up [THEN UU_I, symmetric])

    subsection {* Continuity of @{term Iup} and @{term Ifup} *}

    text {* continuity for @{term Iup} *}

    lemma cont_Iup: "cont Iup"
    apply (rule contI)
    apply (rule is_lub_Iup)
    apply (erule thelubE [OF _ refl])
    done

    text {* continuity for @{term Ifup} *}

    lemma cont_Ifup1: "cont (λf. Ifup f x)"
    by (induct x, simp_all)

    lemma monofun_Ifup2: "monofun (λx. Ifup f x)"
    apply (rule monofunI)
    apply (case_tac x, simp)
    apply (case_tac y, simp)
    apply (simp add: monofun_cfun_arg)
    done

    lemma cont_Ifup2: "cont (λx. Ifup f x)"
    apply (rule contI)
    apply (frule up_chain_cases, safe)
    apply (rule_tac j1="j" in is_lub_range_shift [THEN iffD1])
    apply (erule monofun_Ifup2 [THEN ch2ch_monofun])
    apply (simp add: cont_cfun_arg)
    apply (simp add: thelub_const lub_const)
    done

    subsection {* Continuous versions of constants *}

    constdefs
      up  :: "'a -> 'a u"
      "up ≡ Λ x. Iup x"

      fup :: "('a -> 'b::pcpo) -> 'a u -> 'b"
      "fup ≡ Λ f p. Ifup f p"

    translations
    "case l of up·x => t" == "fup·(LAM x. t)·l"

    text {* continuous versions of lemmas for @{typ "('a)u"} *}

    lemma Exh_Up: "z = ⊥ ∨ (∃x. z = up·x)"
    apply (induct z)
    apply (simp add: inst_up_pcpo)
    apply (simp add: up_def cont_Iup)
    done

    lemma up_eq [simp]: "(up·x = up·y) = (x = y)"
    by (simp add: up_def cont_Iup)

    lemma up_inject: "up·x = up·y ==> x = y"
    by simp

    lemma up_defined [simp]: " up·x ≠ ⊥"
    by (simp add: up_def cont_Iup inst_up_pcpo)

    lemma not_up_less_UU [simp]: "¬ up·x \<sqsubseteq> ⊥"
    by (simp add: eq_UU_iff [symmetric])

    lemma up_less [simp]: "(up·x \<sqsubseteq> up·y) = (x \<sqsubseteq> y)"
    by (simp add: up_def cont_Iup)

    lemma upE: "[|p = ⊥ ==> Q; !!x. p = up·x ==> Q|] ==> Q"
    apply (case_tac p)
    apply (simp add: inst_up_pcpo)
    apply (simp add: up_def cont_Iup)
    done

    lemma fup1 [simp]: "fup·f·⊥ = ⊥"
    by (simp add: fup_def cont_Ifup1 cont_Ifup2 inst_up_pcpo)

    lemma fup2 [simp]: "fup·f·(up·x) = f·x"
    by (simp add: up_def fup_def cont_Iup cont_Ifup1 cont_Ifup2)

    lemma fup3 [simp]: "fup·up·x = x"
    by (rule_tac p=x in upE, simp_all)

    end

### Definition of new type for lifting

### Ordering on type @{typ "'a u"}

lemma minimal_up:

      Ibottom << z

lemma not_Iup_less:

      ¬ Iup x << Ibottom

lemma Iup_less:

      Iup x << Iup y = x << y

### Type @{typ "'a u"} is a partial order

lemma refl_less_up:

      x << x

lemma antisym_less_up:

      [| x << y; y << x |] ==> x = y

lemma trans_less_up:

      [| x << y; y << z |] ==> x << z

### Type @{typ "'a u"} is a cpo

lemma is_lub_Iup:

      range S <<| x ==> range (%i. Iup (S i)) <<| Iup x

lemma up_lemma1:

      z ≠ Ibottom ==> Iup (THE a. Iup a = z) = z

lemma up_lemma2:

      [| chain Y; Y j ≠ Ibottom |] ==> Y (i + j) ≠ Ibottom

lemma up_lemma3:

      [| chain Y; Y j ≠ Ibottom |] ==> Iup (THE a. Iup a = Y (i + j)) = Y (i + j)

lemma up_lemma4:

      [| chain Y; Y j ≠ Ibottom |] ==> chain (%i. THE a. Iup a = Y (i + j))

lemma up_lemma5:

      [| chain Y; Y j ≠ Ibottom |]
      ==> (%i. Y (i + j)) = (%i. Iup (THE a. Iup a = Y (i + j)))

lemma up_lemma6:

      [| chain Y; Y j ≠ Ibottom |]
      ==> range Y <<| Iup (LUB i. THE a. Iup a = Y (i + j))

lemma up_chain_cases:

      chain Y
      ==> (∃A. chain A ∧
               lub (range Y) = Iup (lub (range A)) ∧
               (∃j. ∀i. Y (i + j) = Iup (A i))) ∨
          Y = (%i. Ibottom)

lemma cpo_up:

      chain Y ==> ∃x. range Y <<| x

### Type @{typ "'a u"} is pointed

lemma least_up:

      ∃x. ∀y. x << y

lemma inst_up_pcpo:

      UU = Ibottom

### Continuity of @{term Iup} and @{term Ifup}

lemma cont_Iup:

      cont Iup

lemma cont_Ifup1:

      cont (%f. Ifup f x)

lemma monofun_Ifup2:

      monofun (Ifup f)

lemma cont_Ifup2:

      cont (Ifup f)

### Continuous versions of constants

lemma Exh_Up:

      z = UU ∨ (∃x. z = up·x)

lemma up_eq:

      (up·x = up·y) = (x = y)

lemma up_inject:

      up·x = up·y ==> x = y

lemma up_defined:

      up·x ≠ UU

lemma not_up_less_UU:

      ¬ up·x << UU

lemma up_less:

      up·x << up·y = x << y

lemma upE:

      [| p = UU ==> Q; !!x. p = up·x ==> Q |] ==> Q

lemma fup1:

      fup·f·UU = UU

lemma fup2:

      fup·f·(up·x) = f·x

lemma fup3:

      fup·up·x = x