diff -r f493a20feeb3 -r 04b5e904a220 thys3/PDerivs.thy --- a/thys3/PDerivs.thy Sat Apr 30 00:50:08 2022 +0100 +++ /dev/null Thu Jan 01 00:00:00 1970 +0000 @@ -1,603 +0,0 @@ - -theory PDerivs - imports PosixSpec -begin - - - -abbreviation - "SEQs rs r \ (\r' \ rs. {SEQ r' r})" - -lemma SEQs_eq_image: - "SEQs rs r = (\r'. SEQ r' r) ` rs" - by auto - -fun - pder :: "char \ rexp \ rexp set" -where - "pder c ZERO = {}" -| "pder c ONE = {}" -| "pder c (CH d) = (if c = d then {ONE} else {})" -| "pder c (ALT r1 r2) = (pder c r1) \ (pder c r2)" -| "pder c (SEQ r1 r2) = - (if nullable r1 then SEQs (pder c r1) r2 \ pder c r2 else SEQs (pder c r1) r2)" -| "pder c (STAR r) = SEQs (pder c r) (STAR r)" - -fun - pders :: "char list \ rexp \ rexp set" -where - "pders [] r = {r}" -| "pders (c # s) r = \ (pders s ` pder c r)" - -abbreviation - pder_set :: "char \ rexp set \ rexp set" -where - "pder_set c rs \ \ (pder c ` rs)" - -abbreviation - pders_set :: "char list \ rexp set \ rexp set" -where - "pders_set s rs \ \ (pders s ` rs)" - -lemma pders_append: - "pders (s1 @ s2) r = \ (pders s2 ` pders s1 r)" -by (induct s1 arbitrary: r) (simp_all) - -lemma pders_snoc: - shows "pders (s @ [c]) r = pder_set c (pders s r)" -by (simp add: pders_append) - -lemma pders_simps [simp]: - shows "pders s ZERO = (if s = [] then {ZERO} else {})" - and "pders s ONE = (if s = [] then {ONE} else {})" - and "pders s (ALT r1 r2) = (if s = [] then {ALT r1 r2} else (pders s r1) \ (pders s r2))" -by (induct s) (simp_all) - -lemma pders_CHAR: - shows "pders s (CH c) \ {CH c, ONE}" -by (induct s) (simp_all) - -subsection \Relating left-quotients and partial derivatives\ - -lemma Sequ_UNION_distrib: -shows "A ;; \(M ` I) = \((\i. A ;; M i) ` I)" -and "\(M ` I) ;; A = \((\i. M i ;; A) ` I)" -by (auto simp add: Sequ_def) - - -lemma Der_pder: - shows "Der c (L r) = \ (L ` pder c r)" -by (induct r) (simp_all add: nullable_correctness Sequ_UNION_distrib) - -lemma Ders_pders: - shows "Ders s (L r) = \ (L ` pders s r)" -proof (induct s arbitrary: r) - case (Cons c s) - have ih: "\r. Ders s (L r) = \ (L ` pders s r)" by fact - have "Ders (c # s) (L r) = Ders s (Der c (L r))" by (simp add: Ders_def Der_def) - also have "\ = Ders s (\ (L ` pder c r))" by (simp add: Der_pder) - also have "\ = (\A\(L ` (pder c r)). (Ders s A))" - by (auto simp add: Ders_def) - also have "\ = \ (L ` (pders_set s (pder c r)))" - using ih by auto - also have "\ = \ (L ` (pders (c # s) r))" by simp - finally show "Ders (c # s) (L r) = \ (L ` pders (c # s) r)" . -qed (simp add: Ders_def) - -subsection \Relating derivatives and partial derivatives\ - -lemma der_pder: - shows "\ (L ` (pder c r)) = L (der c r)" -unfolding der_correctness Der_pder by simp - -lemma ders_pders: - shows "\ (L ` (pders s r)) = L (ders s r)" -unfolding der_correctness ders_correctness Ders_pders by simp - - -subsection \Finiteness property of partial derivatives\ - -definition - pders_Set :: "string set \ rexp \ rexp set" -where - "pders_Set A r \ \x \ A. pders x r" - -lemma pders_Set_subsetI: - assumes "\s. s \ A \ pders s r \ C" - shows "pders_Set A r \ C" -using assms unfolding pders_Set_def by (rule UN_least) - -lemma pders_Set_union: - shows "pders_Set (A \ B) r = (pders_Set A r \ pders_Set B r)" -by (simp add: pders_Set_def) - -lemma pders_Set_subset: - shows "A \ B \ pders_Set A r \ pders_Set B r" -by (auto simp add: pders_Set_def) - -definition - "UNIV1 \ UNIV - {[]}" - -lemma pders_Set_ZERO [simp]: - shows "pders_Set UNIV1 ZERO = {}" -unfolding UNIV1_def pders_Set_def by auto - -lemma pders_Set_ONE [simp]: - shows "pders_Set UNIV1 ONE = {}" -unfolding UNIV1_def pders_Set_def by (auto split: if_splits) - -lemma pders_Set_CHAR [simp]: - shows "pders_Set UNIV1 (CH c) = {ONE}" -unfolding UNIV1_def pders_Set_def -apply(auto) -apply(frule rev_subsetD) -apply(rule pders_CHAR) -apply(simp) -apply(case_tac xa) -apply(auto split: if_splits) -done - -lemma pders_Set_ALT [simp]: - shows "pders_Set UNIV1 (ALT r1 r2) = pders_Set UNIV1 r1 \ pders_Set UNIV1 r2" -unfolding UNIV1_def pders_Set_def by auto - - -text \Non-empty suffixes of a string (needed for the cases of @{const SEQ} and @{const STAR} below)\ - -definition - "PSuf s \ {v. v \ [] \ (\u. u @ v = s)}" - -lemma PSuf_snoc: - shows "PSuf (s @ [c]) = (PSuf s) ;; {[c]} \ {[c]}" -unfolding PSuf_def Sequ_def -by (auto simp add: append_eq_append_conv2 append_eq_Cons_conv) - -lemma PSuf_Union: - shows "(\v \ PSuf s ;; {[c]}. f v) = (\v \ PSuf s. f (v @ [c]))" -by (auto simp add: Sequ_def) - -lemma pders_Set_snoc: - shows "pders_Set (PSuf s ;; {[c]}) r = (pder_set c (pders_Set (PSuf s) r))" -unfolding pders_Set_def -by (simp add: PSuf_Union pders_snoc) - -lemma pders_SEQ: - shows "pders s (SEQ r1 r2) \ SEQs (pders s r1) r2 \ (pders_Set (PSuf s) r2)" -proof (induct s rule: rev_induct) - case (snoc c s) - have ih: "pders s (SEQ r1 r2) \ SEQs (pders s r1) r2 \ (pders_Set (PSuf s) r2)" - by fact - have "pders (s @ [c]) (SEQ r1 r2) = pder_set c (pders s (SEQ r1 r2))" - by (simp add: pders_snoc) - also have "\ \ pder_set c (SEQs (pders s r1) r2 \ (pders_Set (PSuf s) r2))" - using ih by fastforce - also have "\ = pder_set c (SEQs (pders s r1) r2) \ pder_set c (pders_Set (PSuf s) r2)" - by (simp) - also have "\ = pder_set c (SEQs (pders s r1) r2) \ pders_Set (PSuf s ;; {[c]}) r2" - by (simp add: pders_Set_snoc) - also - have "\ \ pder_set c (SEQs (pders s r1) r2) \ pder c r2 \ pders_Set (PSuf s ;; {[c]}) r2" - by auto - also - have "\ \ SEQs (pder_set c (pders s r1)) r2 \ pder c r2 \ pders_Set (PSuf s ;; {[c]}) r2" - by (auto simp add: if_splits) - also have "\ = SEQs (pders (s @ [c]) r1) r2 \ pder c r2 \ pders_Set (PSuf s ;; {[c]}) r2" - by (simp add: pders_snoc) - also have "\ \ SEQs (pders (s @ [c]) r1) r2 \ pders_Set (PSuf (s @ [c])) r2" - unfolding pders_Set_def by (auto simp add: PSuf_snoc) - finally show ?case . -qed (simp) - -lemma pders_Set_SEQ_aux1: - assumes a: "s \ UNIV1" - shows "pders_Set (PSuf s) r \ pders_Set UNIV1 r" -using a unfolding UNIV1_def PSuf_def pders_Set_def by auto - -lemma pders_Set_SEQ_aux2: - assumes a: "s \ UNIV1" - shows "SEQs (pders s r1) r2 \ SEQs (pders_Set UNIV1 r1) r2" -using a unfolding pders_Set_def by auto - -lemma pders_Set_SEQ: - shows "pders_Set UNIV1 (SEQ r1 r2) \ SEQs (pders_Set UNIV1 r1) r2 \ pders_Set UNIV1 r2" -apply(rule pders_Set_subsetI) -apply(rule subset_trans) -apply(rule pders_SEQ) -using pders_Set_SEQ_aux1 pders_Set_SEQ_aux2 -apply auto -apply blast -done - -lemma pders_STAR: - assumes a: "s \ []" - shows "pders s (STAR r) \ SEQs (pders_Set (PSuf s) r) (STAR r)" -using a -proof (induct s rule: rev_induct) - case (snoc c s) - have ih: "s \ [] \ pders s (STAR r) \ SEQs (pders_Set (PSuf s) r) (STAR r)" by fact - { assume asm: "s \ []" - have "pders (s @ [c]) (STAR r) = pder_set c (pders s (STAR r))" by (simp add: pders_snoc) - also have "\ \ pder_set c (SEQs (pders_Set (PSuf s) r) (STAR r))" - using ih[OF asm] by fast - also have "\ \ SEQs (pder_set c (pders_Set (PSuf s) r)) (STAR r) \ pder c (STAR r)" - by (auto split: if_splits) - also have "\ \ SEQs (pders_Set (PSuf (s @ [c])) r) (STAR r) \ (SEQs (pder c r) (STAR r))" - by (simp only: PSuf_snoc pders_Set_snoc pders_Set_union) - (auto simp add: pders_Set_def) - also have "\ = SEQs (pders_Set (PSuf (s @ [c])) r) (STAR r)" - by (auto simp add: PSuf_snoc PSuf_Union pders_snoc pders_Set_def) - finally have ?case . - } - moreover - { assume asm: "s = []" - then have ?case by (auto simp add: pders_Set_def pders_snoc PSuf_def) - } - ultimately show ?case by blast -qed (simp) - -lemma pders_Set_STAR: - shows "pders_Set UNIV1 (STAR r) \ SEQs (pders_Set UNIV1 r) (STAR r)" -apply(rule pders_Set_subsetI) -apply(rule subset_trans) -apply(rule pders_STAR) -apply(simp add: UNIV1_def) -apply(simp add: UNIV1_def PSuf_def) -apply(auto simp add: pders_Set_def) -done - -lemma finite_SEQs [simp]: - assumes a: "finite A" - shows "finite (SEQs A r)" -using a by auto - - -lemma finite_pders_Set_UNIV1: - shows "finite (pders_Set UNIV1 r)" -apply(induct r) -apply(simp_all add: - finite_subset[OF pders_Set_SEQ] - finite_subset[OF pders_Set_STAR]) -done - -lemma pders_Set_UNIV: - shows "pders_Set UNIV r = pders [] r \ pders_Set UNIV1 r" -unfolding UNIV1_def pders_Set_def -by blast - -lemma finite_pders_Set_UNIV: - shows "finite (pders_Set UNIV r)" -unfolding pders_Set_UNIV -by (simp add: finite_pders_Set_UNIV1) - -lemma finite_pders_set: - shows "finite (pders_Set A r)" -by (metis finite_pders_Set_UNIV pders_Set_subset rev_finite_subset subset_UNIV) - - -text \The following relationship between the alphabetic width of regular expressions -(called \awidth\ below) and the number of partial derivatives was proved -by Antimirov~\cite{Antimirov95} and formalized by Max Haslbeck.\ - -fun awidth :: "rexp \ nat" where -"awidth ZERO = 0" | -"awidth ONE = 0" | -"awidth (CH a) = 1" | -"awidth (ALT r1 r2) = awidth r1 + awidth r2" | -"awidth (SEQ r1 r2) = awidth r1 + awidth r2" | -"awidth (STAR r1) = awidth r1" - -lemma card_SEQs_pders_Set_le: - shows "card (SEQs (pders_Set A r) s) \ card (pders_Set A r)" - using finite_pders_set - unfolding SEQs_eq_image - by (rule card_image_le) - -lemma card_pders_set_UNIV1_le_awidth: - shows "card (pders_Set UNIV1 r) \ awidth r" -proof (induction r) - case (ALT r1 r2) - have "card (pders_Set UNIV1 (ALT r1 r2)) = card (pders_Set UNIV1 r1 \ pders_Set UNIV1 r2)" by simp - also have "\ \ card (pders_Set UNIV1 r1) + card (pders_Set UNIV1 r2)" - by(simp add: card_Un_le) - also have "\ \ awidth (ALT r1 r2)" using ALT.IH by simp - finally show ?case . -next - case (SEQ r1 r2) - have "card (pders_Set UNIV1 (SEQ r1 r2)) \ card (SEQs (pders_Set UNIV1 r1) r2 \ pders_Set UNIV1 r2)" - by (simp add: card_mono finite_pders_set pders_Set_SEQ) - also have "\ \ card (SEQs (pders_Set UNIV1 r1) r2) + card (pders_Set UNIV1 r2)" - by (simp add: card_Un_le) - also have "\ \ card (pders_Set UNIV1 r1) + card (pders_Set UNIV1 r2)" - by (simp add: card_SEQs_pders_Set_le) - also have "\ \ awidth (SEQ r1 r2)" using SEQ.IH by simp - finally show ?case . -next - case (STAR r) - have "card (pders_Set UNIV1 (STAR r)) \ card (SEQs (pders_Set UNIV1 r) (STAR r))" - by (simp add: card_mono finite_pders_set pders_Set_STAR) - also have "\ \ card (pders_Set UNIV1 r)" by (rule card_SEQs_pders_Set_le) - also have "\ \ awidth (STAR r)" by (simp add: STAR.IH) - finally show ?case . -qed (auto) - -text\Antimirov's Theorem 3.4:\ - -theorem card_pders_set_UNIV_le_awidth: - shows "card (pders_Set UNIV r) \ awidth r + 1" -proof - - have "card (insert r (pders_Set UNIV1 r)) \ Suc (card (pders_Set UNIV1 r))" - by(auto simp: card_insert_if[OF finite_pders_Set_UNIV1]) - also have "\ \ Suc (awidth r)" by(simp add: card_pders_set_UNIV1_le_awidth) - finally show ?thesis by(simp add: pders_Set_UNIV) -qed - -text\Antimirov's Corollary 3.5:\ -(*W stands for word set*) -corollary card_pders_set_le_awidth: - shows "card (pders_Set W r) \ awidth r + 1" -proof - - have "card (pders_Set W r) \ card (pders_Set UNIV r)" - by (simp add: card_mono finite_pders_set pders_Set_subset) - also have "... \ awidth r + 1" - by (rule card_pders_set_UNIV_le_awidth) - finally show "card (pders_Set W r) \ awidth r + 1" by simp -qed - -(* other result by antimirov *) - -lemma card_pders_awidth: - shows "card (pders s r) \ awidth r + 1" -proof - - have "pders s r \ pders_Set UNIV r" - using pders_Set_def by auto - then have "card (pders s r) \ card (pders_Set UNIV r)" - by (simp add: card_mono finite_pders_set) - then show "card (pders s r) \ awidth r + 1" - using card_pders_set_le_awidth order_trans by blast -qed - - - - - -fun subs :: "rexp \ rexp set" where -"subs ZERO = {ZERO}" | -"subs ONE = {ONE}" | -"subs (CH a) = {CH a, ONE}" | -"subs (ALT r1 r2) = (subs r1 \ subs r2 \ {ALT r1 r2})" | -"subs (SEQ r1 r2) = (subs r1 \ subs r2 \ {SEQ r1 r2} \ SEQs (subs r1) r2)" | -"subs (STAR r1) = (subs r1 \ {STAR r1} \ SEQs (subs r1) (STAR r1))" - -lemma subs_finite: - shows "finite (subs r)" - apply(induct r) - apply(simp_all) - done - - - -lemma pders_subs: - shows "pders s r \ subs r" - apply(induct r arbitrary: s) - apply(simp) - apply(simp) - apply(simp add: pders_CHAR) -(* SEQ case *) - apply(simp) - apply(rule subset_trans) - apply(rule pders_SEQ) - defer -(* ALT case *) - apply(simp) - apply(rule impI) - apply(rule conjI) - apply blast - apply blast -(* STAR case *) - apply(case_tac s) - apply(simp) - apply(rule subset_trans) - thm pders_STAR - apply(rule pders_STAR) - apply(simp) - apply(auto simp add: pders_Set_def)[1] - apply(simp) - apply(rule conjI) - apply blast -apply(auto simp add: pders_Set_def)[1] - done - -fun size2 :: "rexp \ nat" where - "size2 ZERO = 1" | - "size2 ONE = 1" | - "size2 (CH c) = 1" | - "size2 (ALT r1 r2) = Suc (size2 r1 + size2 r2)" | - "size2 (SEQ r1 r2) = Suc (size2 r1 + size2 r2)" | - "size2 (STAR r1) = Suc (size2 r1)" - - -lemma size_rexp: - fixes r :: rexp - shows "1 \ size2 r" - apply(induct r) - apply(simp) - apply(simp_all) - done - -lemma subs_size2: - shows "\r1 \ subs r. size2 r1 \ Suc (size2 r * size2 r)" - apply(induct r) - apply(simp) - apply(simp) - apply(simp) -(* SEQ case *) - apply(simp) - apply(auto)[1] - apply (smt Suc_n_not_le_n add.commute distrib_left le_Suc_eq left_add_mult_distrib nat_le_linear trans_le_add1) - apply (smt Suc_le_mono Suc_n_not_le_n le_trans nat_le_linear power2_eq_square power2_sum semiring_normalization_rules(23) trans_le_add2) - apply (smt Groups.add_ac(3) Suc_n_not_le_n distrib_left le_Suc_eq left_add_mult_distrib nat_le_linear trans_le_add1) -(* ALT case *) - apply(simp) - apply(auto)[1] - apply (smt Groups.add_ac(2) Suc_le_mono Suc_n_not_le_n le_add2 linear order_trans power2_eq_square power2_sum) - apply (smt Groups.add_ac(2) Suc_le_mono Suc_n_not_le_n left_add_mult_distrib linear mult.commute order.trans trans_le_add1) -(* STAR case *) - apply(auto)[1] - apply(drule_tac x="r'" in bspec) - apply(simp) - apply(rule le_trans) - apply(assumption) - apply(simp) - using size_rexp - apply(simp) - done - -lemma awidth_size: - shows "awidth r \ size2 r" - apply(induct r) - apply(simp_all) - done - -lemma Sum1: - fixes A B :: "nat set" - assumes "A \ B" "finite A" "finite B" - shows "\A \ \B" - using assms - by (simp add: sum_mono2) - -lemma Sum2: - fixes A :: "rexp set" - and f g :: "rexp \ nat" - assumes "finite A" "\x \ A. f x \ g x" - shows "sum f A \ sum g A" - using assms - apply(induct A) - apply(auto) - done - - - - - -lemma pders_max_size: - shows "(sum size2 (pders s r)) \ (Suc (size2 r)) ^ 3" -proof - - have "(sum size2 (pders s r)) \ sum (\_. Suc (size2 r * size2 r)) (pders s r)" - apply(rule_tac Sum2) - apply (meson pders_subs rev_finite_subset subs_finite) - using pders_subs subs_size2 by blast - also have "... \ (Suc (size2 r * size2 r)) * (sum (\_. 1) (pders s r))" - by simp - also have "... \ (Suc (size2 r * size2 r)) * card (pders s r)" - by simp - also have "... \ (Suc (size2 r * size2 r)) * (Suc (awidth r))" - using Suc_eq_plus1 card_pders_awidth mult_le_mono2 by presburger - also have "... \ (Suc (size2 r * size2 r)) * (Suc (size2 r))" - using Suc_le_mono awidth_size mult_le_mono2 by presburger - also have "... \ (Suc (size2 r)) ^ 3" - by (smt One_nat_def Suc_1 Suc_mult_le_cancel1 Suc_n_not_le_n antisym_conv le_Suc_eq mult.commute nat_le_linear numeral_3_eq_3 power2_eq_square power2_le_imp_le power_Suc size_rexp) - finally show ?thesis . -qed - -lemma pders_Set_max_size: - shows "(sum size2 (pders_Set A r)) \ (Suc (size2 r)) ^ 3" -proof - - have "(sum size2 (pders_Set A r)) \ sum (\_. Suc (size2 r * size2 r)) (pders_Set A r)" - apply(rule_tac Sum2) - apply (simp add: finite_pders_set) - by (meson pders_Set_subsetI pders_subs subs_size2 subsetD) - also have "... \ (Suc (size2 r * size2 r)) * (sum (\_. 1) (pders_Set A r))" - by simp - also have "... \ (Suc (size2 r * size2 r)) * card (pders_Set A r)" - by simp - also have "... \ (Suc (size2 r * size2 r)) * (Suc (awidth r))" - using Suc_eq_plus1 card_pders_set_le_awidth mult_le_mono2 by presburger - also have "... \ (Suc (size2 r * size2 r)) * (Suc (size2 r))" - using Suc_le_mono awidth_size mult_le_mono2 by presburger - also have "... \ (Suc (size2 r)) ^ 3" - by (smt One_nat_def Suc_1 Suc_mult_le_cancel1 Suc_n_not_le_n antisym_conv le_Suc_eq mult.commute nat_le_linear numeral_3_eq_3 power2_eq_square power2_le_imp_le power_Suc size_rexp) - finally show ?thesis . -qed - -fun height :: "rexp \ nat" where - "height ZERO = 1" | - "height ONE = 1" | - "height (CH c) = 1" | - "height (ALT r1 r2) = Suc (max (height r1) (height r2))" | - "height (SEQ r1 r2) = Suc (max (height r1) (height r2))" | - "height (STAR r1) = Suc (height r1)" - -lemma height_size2: - shows "height r \ size2 r" - apply(induct r) - apply(simp_all) - done - -lemma height_rexp: - fixes r :: rexp - shows "1 \ height r" - apply(induct r) - apply(simp_all) - done - -lemma subs_height: - shows "\r1 \ subs r. height r1 \ Suc (height r)" - apply(induct r) - apply(auto)+ - done - -fun lin_concat :: "(char \ rexp) \ rexp \ (char \ rexp)" (infixl "[.]" 91) - where -"(c, ZERO) [.] t = (c, ZERO)" -| "(c, ONE) [.] t = (c, t)" -| "(c, p) [.] t = (c, SEQ p t)" - - -fun circle_concat :: "(char \ rexp ) set \ rexp \ (char \ rexp) set" ( infixl "\" 90) - where -"l \ ZERO = {}" -| "l \ ONE = l" -| "l \ t = ( (\p. p [.] t) ` l ) " - - - -fun linear_form :: "rexp \( char \ rexp ) set" - where - "linear_form ZERO = {}" -| "linear_form ONE = {}" -| "linear_form (CH c) = {(c, ONE)}" -| "linear_form (ALT r1 r2) = (linear_form) r1 \ (linear_form r2)" -| "linear_form (SEQ r1 r2) = (if (nullable r1) then (linear_form r1) \ r2 \ linear_form r2 else (linear_form r1) \ r2) " -| "linear_form (STAR r ) = (linear_form r) \ (STAR r)" - - -value "linear_form (SEQ (STAR (CH x)) (STAR (ALT (SEQ (CH x) (CH x)) (CH y) )) )" - - -value "linear_form (STAR (ALT (SEQ (CH x) (CH x)) (CH y) )) " - -fun pdero :: "char \ rexp \ rexp set" - where -"pdero c t = \ ((\(d, p). if d = c then {p} else {}) ` (linear_form t) )" - -fun pderso :: "char list \ rexp \ rexp set" - where - "pderso [] r = {r}" -| "pderso (c # s) r = \ ( pderso s ` (pdero c r) )" - -lemma pdero_result: - shows "pdero c (STAR (ALT (CH c) (SEQ (CH c) (CH c)))) = {SEQ (CH c)(STAR (ALT (CH c) (SEQ (CH c) (CH c)))),(STAR (ALT (CH c) (SEQ (CH c) (CH c))))}" - apply(simp) - by auto - -fun concatLen :: "rexp \ nat" where -"concatLen ZERO = 0" | -"concatLen ONE = 0" | -"concatLen (CH c) = 0" | -"concatLen (SEQ v1 v2) = Suc (max (concatLen v1) (concatLen v2))" | -" concatLen (ALT v1 v2) = max (concatLen v1) (concatLen v2)" | -" concatLen (STAR v) = Suc (concatLen v)" - - - -end \ No newline at end of file