(*  Title:      HOL/Imperative_HOL/Array.thy

    Author:     John Matthews, Galois Connections; Alexander Krauss, Lukas Bulwahn & Florian Haftmann, TU Muenchen

*)

header {* Monadic arrays *}

theory Array

imports Heap_Monad

begin

subsection {* Primitives *}

definition present :: "heap \<Rightarrow> 'a\<Colon>heap array \<Rightarrow> bool" where

  "present h a \<longleftrightarrow> addr_of_array a < lim h"

definition (*FIXME get :: "heap \<Rightarrow> 'a\<Colon>heap array \<Rightarrow> 'a list" where*)

  get_array :: "'a\<Colon>heap array \<Rightarrow> heap \<Rightarrow> 'a list" where

  "get_array a h = map from_nat (arrays h (TYPEREP('a)) (addr_of_array a))"

definition set :: "'a\<Colon>heap array \<Rightarrow> 'a list \<Rightarrow> heap \<Rightarrow> heap" where

  "set a x = arrays_update (\<lambda>h. h(TYPEREP('a) := ((h(TYPEREP('a))) (addr_of_array a:=map to_nat x))))"

definition alloc :: "'a list \<Rightarrow> heap \<Rightarrow> 'a\<Colon>heap array \<times> heap" where

  "alloc xs h = (let

     l = lim h;

     r = Array l;

     h'' = set r xs (h\<lparr>lim := l + 1\<rparr>)

   in (r, h''))"

definition length :: "heap \<Rightarrow> 'a\<Colon>heap array \<Rightarrow> nat" where

  "length h a = List.length (get_array a h)"

definition update :: "'a\<Colon>heap array \<Rightarrow> nat \<Rightarrow> 'a \<Rightarrow> heap \<Rightarrow> heap" where

  "update a i x h = set a ((get_array a h)[i:=x]) h"

definition noteq :: "'a\<Colon>heap array \<Rightarrow> 'b\<Colon>heap array \<Rightarrow> bool" (infix "=!!=" 70) where

  "r =!!= s \<longleftrightarrow> TYPEREP('a) \<noteq> TYPEREP('b) \<or> addr_of_array r \<noteq> addr_of_array s"

subsection {* Monad operations *}

definition new :: "nat \<Rightarrow> 'a\<Colon>heap \<Rightarrow> 'a array Heap" where

  [code del]: "new n x = Heap_Monad.heap (alloc (replicate n x))"

definition of_list :: "'a\<Colon>heap list \<Rightarrow> 'a array Heap" where

  [code del]: "of_list xs = Heap_Monad.heap (alloc xs)"

definition make :: "nat \<Rightarrow> (nat \<Rightarrow> 'a\<Colon>heap) \<Rightarrow> 'a array Heap" where

  [code del]: "make n f = Heap_Monad.heap (alloc (map f [0 ..< n]))"

definition len :: "'a\<Colon>heap array \<Rightarrow> nat Heap" where

  [code del]: "len a = Heap_Monad.tap (\<lambda>h. length h a)"

definition nth :: "'a\<Colon>heap array \<Rightarrow> nat \<Rightarrow> 'a Heap" where

  [code del]: "nth a i = Heap_Monad.guard (\<lambda>h. i < length h a)

    (\<lambda>h. (get_array a h ! i, h))"

definition upd :: "nat \<Rightarrow> 'a \<Rightarrow> 'a\<Colon>heap array \<Rightarrow> 'a\<Colon>heap array Heap" where

  [code del]: "upd i x a = Heap_Monad.guard (\<lambda>h. i < length h a)

    (\<lambda>h. (a, update a i x h))"

definition map_entry :: "nat \<Rightarrow> ('a\<Colon>heap \<Rightarrow> 'a) \<Rightarrow> 'a array \<Rightarrow> 'a array Heap" where

  [code del]: "map_entry i f a = Heap_Monad.guard (\<lambda>h. i < length h a)

    (\<lambda>h. (a, update a i (f (get_array a h ! i)) h))"

definition swap :: "nat \<Rightarrow> 'a \<Rightarrow> 'a\<Colon>heap array \<Rightarrow> 'a Heap" where

  [code del]: "swap i x a = Heap_Monad.guard (\<lambda>h. i < length h a)

    (\<lambda>h. (get_array a h ! i, update a i x h))"

definition freeze :: "'a\<Colon>heap array \<Rightarrow> 'a list Heap" where

  [code del]: "freeze a = Heap_Monad.tap (\<lambda>h. get_array a h)"

subsection {* Properties *}

text {* FIXME: Does there exist a "canonical" array axiomatisation in

the literature?  *}

text {* Primitives *}

lemma noteq_arrs_sym: "a =!!= b \<Longrightarrow> b =!!= a"

  and unequal_arrs [simp]: "a \<noteq> a' \<longleftrightarrow> a =!!= a'"

  unfolding noteq_def by auto

lemma noteq_arrs_irrefl: "r =!!= r \<Longrightarrow> False"

  unfolding noteq_def by auto

lemma present_new_arr: "present h a \<Longrightarrow> a =!!= fst (alloc xs h)"

  by (simp add: present_def noteq_def alloc_def Let_def)

lemma array_get_set_eq [simp]: "get_array r (set r x h) = x"

  by (simp add: get_array_def set_def o_def)

lemma array_get_set_neq [simp]: "r =!!= s \<Longrightarrow> get_array r (set s x h) = get_array r h"

  by (simp add: noteq_def get_array_def set_def)

lemma set_array_same [simp]:

  "set r x (set r y h) = set r x h"

  by (simp add: set_def)

lemma array_set_set_swap:

  "r =!!= r' \<Longrightarrow> set r x (set r' x' h) = set r' x' (set r x h)"

  by (simp add: Let_def expand_fun_eq noteq_def set_def)

lemma get_array_update_eq [simp]:

  "get_array a (update a i v h) = (get_array a h) [i := v]"

  by (simp add: update_def)

lemma nth_update_array_neq_array [simp]:

  "a =!!= b \<Longrightarrow> get_array a (update b j v h) ! i = get_array a h ! i"

  by (simp add: update_def noteq_def)

lemma get_arry_array_update_elem_neqIndex [simp]:

  "i \<noteq> j \<Longrightarrow> get_array a (update a j v h) ! i = get_array a h ! i"

  by simp

lemma length_update [simp]: 

  "length (update b i v h) = length h"

  by (simp add: update_def length_def set_def get_array_def expand_fun_eq)

lemma update_swap_neqArray:

  "a =!!= a' \<Longrightarrow> 

  update a i v (update a' i' v' h) 

  = update a' i' v' (update a i v h)"

apply (unfold update_def)

apply simp

apply (subst array_set_set_swap, assumption)

apply (subst array_get_set_neq)

apply (erule noteq_arrs_sym)

apply (simp)

done

lemma update_swap_neqIndex:

  "\<lbrakk> i \<noteq> i' \<rbrakk> \<Longrightarrow> update a i v (update a i' v' h) = update a i' v' (update a i v h)"

  by (auto simp add: update_def array_set_set_swap list_update_swap)

lemma get_array_init_array_list:

  "get_array (fst (alloc ls h)) (snd (alloc ls' h)) = ls'"

  by (simp add: Let_def split_def alloc_def)

lemma set_array:

  "set (fst (alloc ls h))

     new_ls (snd (alloc ls h))

       = snd (alloc new_ls h)"

  by (simp add: Let_def split_def alloc_def)

lemma array_present_update [simp]: 

  "present (update b i v h) = present h"

  by (simp add: update_def present_def set_def get_array_def expand_fun_eq)

lemma array_present_array [simp]:

  "present (snd (alloc xs h)) (fst (alloc xs h))"

  by (simp add: present_def alloc_def set_def Let_def)

lemma not_array_present_array [simp]:

  "\<not> present h (fst (alloc xs h))"

  by (simp add: present_def alloc_def Let_def)

text {* Monad operations *}

lemma execute_new [execute_simps]:

  "execute (new n x) h = Some (alloc (replicate n x) h)"

  by (simp add: new_def execute_simps)

lemma success_newI [success_intros]:

  "success (new n x) h"

  by (auto intro: success_intros simp add: new_def)

lemma crel_newI [crel_intros]:

  assumes "(a, h') = alloc (replicate n x) h"

  shows "crel (new n x) h h' a"

  by (rule crelI) (simp add: assms execute_simps)

lemma crel_newE [crel_elims]:

  assumes "crel (new n x) h h' r"

  obtains "r = fst (alloc (replicate n x) h)" "h' = snd (alloc (replicate n x) h)" 

    "get_array r h' = replicate n x" "present h' r" "\<not> present h r"

  using assms by (rule crelE) (simp add: get_array_init_array_list execute_simps)

lemma execute_of_list [execute_simps]:

  "execute (of_list xs) h = Some (alloc xs h)"

  by (simp add: of_list_def execute_simps)

lemma success_of_listI [success_intros]:

  "success (of_list xs) h"

  by (auto intro: success_intros simp add: of_list_def)

lemma crel_of_listI [crel_intros]:

  assumes "(a, h') = alloc xs h"

  shows "crel (of_list xs) h h' a"

  by (rule crelI) (simp add: assms execute_simps)

lemma crel_of_listE [crel_elims]:

  assumes "crel (of_list xs) h h' r"

  obtains "r = fst (alloc xs h)" "h' = snd (alloc xs h)" 

    "get_array r h' = xs" "present h' r" "\<not> present h r"

  using assms by (rule crelE) (simp add: get_array_init_array_list execute_simps)

lemma execute_make [execute_simps]:

  "execute (make n f) h = Some (alloc (map f [0 ..< n]) h)"

  by (simp add: make_def execute_simps)

lemma success_makeI [success_intros]:

  "success (make n f) h"

  by (auto intro: success_intros simp add: make_def)

lemma crel_makeI [crel_intros]:

  assumes "(a, h') = alloc (map f [0 ..< n]) h"

  shows "crel (make n f) h h' a"

  by (rule crelI) (simp add: assms execute_simps)

lemma crel_makeE [crel_elims]:

  assumes "crel (make n f) h h' r"

  obtains "r = fst (alloc (map f [0 ..< n]) h)" "h' = snd (alloc (map f [0 ..< n]) h)" 

    "get_array r h' = map f [0 ..< n]" "present h' r" "\<not> present h r"

  using assms by (rule crelE) (simp add: get_array_init_array_list execute_simps)

lemma execute_len [execute_simps]:

  "execute (len a) h = Some (length h a, h)"

  by (simp add: len_def execute_simps)

lemma success_lenI [success_intros]:

  "success (len a) h"

  by (auto intro: success_intros simp add: len_def)

lemma crel_lengthI [crel_intros]:

  assumes "h' = h" "r = length h a"

  shows "crel (len a) h h' r"

  by (rule crelI) (simp add: assms execute_simps)

lemma crel_lengthE [crel_elims]:

  assumes "crel (len a) h h' r"

  obtains "r = length h' a" "h' = h" 

  using assms by (rule crelE) (simp add: execute_simps)

lemma execute_nth [execute_simps]:

  "i < length h a \<Longrightarrow>

    execute (nth a i) h = Some (get_array a h ! i, h)"

  "i \<ge> length h a \<Longrightarrow> execute (nth a i) h = None"

  by (simp_all add: nth_def execute_simps)

lemma success_nthI [success_intros]:

  "i < length h a \<Longrightarrow> success (nth a i) h"

  by (auto intro: success_intros simp add: nth_def)

lemma crel_nthI [crel_intros]:

  assumes "i < length h a" "h' = h" "r = get_array a h ! i"

  shows "crel (nth a i) h h' r"

  by (rule crelI) (insert assms, simp add: execute_simps)

lemma crel_nthE [crel_elims]:

  assumes "crel (nth a i) h h' r"

  obtains "i < length h a" "r = get_array a h ! i" "h' = h"

  using assms by (rule crelE)

    (erule successE, cases "i < length h a", simp_all add: execute_simps)

lemma execute_upd [execute_simps]:

  "i < length h a \<Longrightarrow>

    execute (upd i x a) h = Some (a, update a i x h)"

  "i \<ge> length h a \<Longrightarrow> execute (upd i x a) h = None"

  by (simp_all add: upd_def execute_simps)

lemma success_updI [success_intros]:

  "i < length h a \<Longrightarrow> success (upd i x a) h"

  by (auto intro: success_intros simp add: upd_def)

lemma crel_updI [crel_intros]:

  assumes "i < length h a" "h' = update a i v h"

  shows "crel (upd i v a) h h' a"

  by (rule crelI) (insert assms, simp add: execute_simps)

lemma crel_updE [crel_elims]:

  assumes "crel (upd i v a) h h' r"

  obtains "r = a" "h' = update a i v h" "i < length h a"

  using assms by (rule crelE)

    (erule successE, cases "i < length h a", simp_all add: execute_simps)

lemma execute_map_entry [execute_simps]:

  "i < length h a \<Longrightarrow>

   execute (map_entry i f a) h =

      Some (a, update a i (f (get_array a h ! i)) h)"

  "i \<ge> length h a \<Longrightarrow> execute (map_entry i f a) h = None"

  by (simp_all add: map_entry_def execute_simps)

lemma success_map_entryI [success_intros]:

  "i < length h a \<Longrightarrow> success (map_entry i f a) h"

  by (auto intro: success_intros simp add: map_entry_def)

lemma crel_map_entryI [crel_intros]:

  assumes "i < length h a" "h' = update a i (f (get_array a h ! i)) h" "r = a"

  shows "crel (map_entry i f a) h h' r"

  by (rule crelI) (insert assms, simp add: execute_simps)

lemma crel_map_entryE [crel_elims]:

  assumes "crel (map_entry i f a) h h' r"

  obtains "r = a" "h' = update a i (f (get_array a h ! i)) h" "i < length h a"

  using assms by (rule crelE)

    (erule successE, cases "i < length h a", simp_all add: execute_simps)

lemma execute_swap [execute_simps]:

  "i < length h a \<Longrightarrow>

   execute (swap i x a) h =

      Some (get_array a h ! i, update a i x h)"

  "i \<ge> length h a \<Longrightarrow> execute (swap i x a) h = None"

  by (simp_all add: swap_def execute_simps)

lemma success_swapI [success_intros]:

  "i < length h a \<Longrightarrow> success (swap i x a) h"

  by (auto intro: success_intros simp add: swap_def)

lemma crel_swapI [crel_intros]:

  assumes "i < length h a" "h' = update a i x h" "r = get_array a h ! i"

  shows "crel (swap i x a) h h' r"

  by (rule crelI) (insert assms, simp add: execute_simps)

lemma crel_swapE [crel_elims]:

  assumes "crel (swap i x a) h h' r"

  obtains "r = get_array a h ! i" "h' = update a i x h" "i < length h a"

  using assms by (rule crelE)

    (erule successE, cases "i < length h a", simp_all add: execute_simps)

lemma execute_freeze [execute_simps]:

  "execute (freeze a) h = Some (get_array a h, h)"

  by (simp add: freeze_def execute_simps)

lemma success_freezeI [success_intros]:

  "success (freeze a) h"

  by (auto intro: success_intros simp add: freeze_def)

lemma crel_freezeI [crel_intros]:

  assumes "h' = h" "r = get_array a h"

  shows "crel (freeze a) h h' r"

  by (rule crelI) (insert assms, simp add: execute_simps)

lemma crel_freezeE [crel_elims]:

  assumes "crel (freeze a) h h' r"

  obtains "h' = h" "r = get_array a h"

  using assms by (rule crelE) (simp add: execute_simps)

lemma upd_return:

  "upd i x a \<guillemotright> return a = upd i x a"

  by (rule Heap_eqI) (simp add: bind_def guard_def upd_def execute_simps)

lemma array_make:

  "new n x = make n (\<lambda>_. x)"

  by (rule Heap_eqI) (simp add: map_replicate_trivial execute_simps)

lemma array_of_list_make:

  "of_list xs = make (List.length xs) (\<lambda>n. xs ! n)"

  by (rule Heap_eqI) (simp add: map_nth execute_simps)

hide_const (open) present (*get*) set alloc length update noteq new of_list make len nth upd map_entry swap freeze

subsection {* Code generator setup *}

subsubsection {* Logical intermediate layer *}

definition new' where

  [code del]: "new' = Array.new o Code_Numeral.nat_of"

lemma [code]:

  "Array.new = new' o Code_Numeral.of_nat"

  by (simp add: new'_def o_def)

definition of_list' where

  [code del]: "of_list' i xs = Array.of_list (take (Code_Numeral.nat_of i) xs)"

lemma [code]:

  "Array.of_list xs = of_list' (Code_Numeral.of_nat (List.length xs)) xs"

  by (simp add: of_list'_def)

definition make' where

  [code del]: "make' i f = Array.make (Code_Numeral.nat_of i) (f o Code_Numeral.of_nat)"

lemma [code]:

  "Array.make n f = make' (Code_Numeral.of_nat n) (f o Code_Numeral.nat_of)"

  by (simp add: make'_def o_def)

definition len' where

  [code del]: "len' a = Array.len a \<guillemotright>= (\<lambda>n. return (Code_Numeral.of_nat n))"

lemma [code]:

  "Array.len a = len' a \<guillemotright>= (\<lambda>i. return (Code_Numeral.nat_of i))"

  by (simp add: len'_def)

definition nth' where

  [code del]: "nth' a = Array.nth a o Code_Numeral.nat_of"

lemma [code]:

  "Array.nth a n = nth' a (Code_Numeral.of_nat n)"

  by (simp add: nth'_def)

definition upd' where

  [code del]: "upd' a i x = Array.upd (Code_Numeral.nat_of i) x a \<guillemotright> return ()"

lemma [code]:

  "Array.upd i x a = upd' a (Code_Numeral.of_nat i) x \<guillemotright> return a"

  by (simp add: upd'_def upd_return)

lemma [code]:

  "Array.map_entry i f a = do {

     x \<leftarrow> Array.nth a i;

     Array.upd i (f x) a

   }"

  by (rule Heap_eqI) (simp add: bind_def guard_def map_entry_def execute_simps)

lemma [code]:

  "Array.swap i x a = do {

     y \<leftarrow> Array.nth a i;

     Array.upd i x a;

     return y

   }"

  by (rule Heap_eqI) (simp add: bind_def guard_def swap_def execute_simps)

lemma [code]:

  "Array.freeze a = do {

     n \<leftarrow> Array.len a;

     Heap_Monad.fold_map (\<lambda>i. Array.nth a i) [0..<n]

   }"

proof (rule Heap_eqI)

  fix h

  have *: "List.map

     (\<lambda>x. fst (the (if x < Array.length h a

                    then Some (get_array a h ! x, h) else None)))

     [0..<Array.length h a] =

       List.map (List.nth (get_array a h)) [0..<Array.length h a]"

    by simp

  have "execute (Heap_Monad.fold_map (Array.nth a) [0..<Array.length h a]) h =

    Some (get_array a h, h)"

    apply (subst execute_fold_map_unchanged_heap)

    apply (simp_all add: nth_def guard_def *)

    apply (simp add: length_def map_nth)

    done

  then have "execute (do {

      n \<leftarrow> Array.len a;

      Heap_Monad.fold_map (Array.nth a) [0..<n]

    }) h = Some (get_array a h, h)"

    by (auto intro: execute_bind_eq_SomeI simp add: execute_simps)

  then show "execute (Array.freeze a) h = execute (do {

      n \<leftarrow> Array.len a;

      Heap_Monad.fold_map (Array.nth a) [0..<n]

    }) h" by (simp add: execute_simps)

qed

hide_const (open) new' of_list' make' len' nth' upd'

text {* SML *}

code_type array (SML "_/ array")

code_const Array (SML "raise/ (Fail/ \"bare Array\")")

code_const Array.new' (SML "(fn/ ()/ =>/ Array.array/ ((_),/ (_)))")

code_const Array.of_list' (SML "(fn/ ()/ =>/ Array.fromList/ _)")

code_const Array.make' (SML "(fn/ ()/ =>/ Array.tabulate/ ((_),/ (_)))")

code_const Array.len' (SML "(fn/ ()/ =>/ Array.length/ _)")

code_const Array.nth' (SML "(fn/ ()/ =>/ Array.sub/ ((_),/ (_)))")

code_const Array.upd' (SML "(fn/ ()/ =>/ Array.update/ ((_),/ (_),/ (_)))")

code_reserved SML Array

text {* OCaml *}

code_type array (OCaml "_/ array")

code_const Array (OCaml "failwith/ \"bare Array\"")

code_const Array.new' (OCaml "(fun/ ()/ ->/ Array.make/ (Big'_int.int'_of'_big'_int/ _)/ _)")

code_const Array.of_list' (OCaml "(fun/ ()/ ->/ Array.of'_list/ _)")

code_const Array.len' (OCaml "(fun/ ()/ ->/ Big'_int.big'_int'_of'_int/ (Array.length/ _))")

code_const Array.nth' (OCaml "(fun/ ()/ ->/ Array.get/ _/ (Big'_int.int'_of'_big'_int/ _))")

code_const Array.upd' (OCaml "(fun/ ()/ ->/ Array.set/ _/ (Big'_int.int'_of'_big'_int/ _)/ _)")

code_reserved OCaml Array

text {* Haskell *}

code_type array (Haskell "Heap.STArray/ Heap.RealWorld/ _")

code_const Array (Haskell "error/ \"bare Array\"")

code_const Array.new' (Haskell "Heap.newArray/ (0,/ _)")

code_const Array.of_list' (Haskell "Heap.newListArray/ (0,/ _)")

code_const Array.len' (Haskell "Heap.lengthArray")

code_const Array.nth' (Haskell "Heap.readArray")

code_const Array.upd' (Haskell "Heap.writeArray")

end