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src/HOL/Library/More_List.thy

author | haftmann |

Thu, 20 May 2010 17:35:02 +0200 | |

changeset 37028 | a6e0696d7110 |

parent 37025 | 8a5718d54e71 |

child 39198 | f967a16dfcdd |

permissions | -rw-r--r-- |

proper document text

(* Author: Florian Haftmann, TU Muenchen *) header {* Operations on lists beyond the standard List theory *} theory More_List imports Main begin hide_const (open) Finite_Set.fold text {* Repairing code generator setup *} declare (in lattice) Inf_fin_set_fold [code_unfold del] declare (in lattice) Sup_fin_set_fold [code_unfold del] declare (in linorder) Min_fin_set_fold [code_unfold del] declare (in linorder) Max_fin_set_fold [code_unfold del] declare (in complete_lattice) Inf_set_fold [code_unfold del] declare (in complete_lattice) Sup_set_fold [code_unfold del] declare rev_foldl_cons [code del] text {* Fold combinator with canonical argument order *} primrec fold :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'a list \<Rightarrow> 'b \<Rightarrow> 'b" where "fold f [] = id" | "fold f (x # xs) = fold f xs \<circ> f x" lemma foldl_fold: "foldl f s xs = fold (\<lambda>x s. f s x) xs s" by (induct xs arbitrary: s) simp_all lemma foldr_fold_rev: "foldr f xs = fold f (rev xs)" by (simp add: foldr_foldl foldl_fold expand_fun_eq) lemma fold_rev_conv [code_unfold]: "fold f (rev xs) = foldr f xs" by (simp add: foldr_fold_rev) lemma fold_cong [fundef_cong, recdef_cong]: "a = b \<Longrightarrow> xs = ys \<Longrightarrow> (\<And>x. x \<in> set xs \<Longrightarrow> f x = g x) \<Longrightarrow> fold f xs a = fold g ys b" by (induct ys arbitrary: a b xs) simp_all lemma fold_id: assumes "\<And>x. x \<in> set xs \<Longrightarrow> f x = id" shows "fold f xs = id" using assms by (induct xs) simp_all lemma fold_apply: assumes "\<And>x. x \<in> set xs \<Longrightarrow> h \<circ> g x = f x \<circ> h" shows "h \<circ> fold g xs = fold f xs \<circ> h" using assms by (induct xs) (simp_all add: expand_fun_eq) lemma fold_invariant: assumes "\<And>x. x \<in> set xs \<Longrightarrow> Q x" and "P s" and "\<And>x s. Q x \<Longrightarrow> P s \<Longrightarrow> P (f x s)" shows "P (fold f xs s)" using assms by (induct xs arbitrary: s) simp_all lemma fold_weak_invariant: assumes "P s" and "\<And>s x. x \<in> set xs \<Longrightarrow> P s \<Longrightarrow> P (f x s)" shows "P (fold f xs s)" using assms by (induct xs arbitrary: s) simp_all lemma fold_append [simp]: "fold f (xs @ ys) = fold f ys \<circ> fold f xs" by (induct xs) simp_all lemma fold_map [code_unfold]: "fold g (map f xs) = fold (g o f) xs" by (induct xs) simp_all lemma fold_rev: assumes "\<And>x y. x \<in> set xs \<Longrightarrow> y \<in> set xs \<Longrightarrow> f y \<circ> f x = f x \<circ> f y" shows "fold f (rev xs) = fold f xs" using assms by (induct xs) (simp_all del: o_apply add: fold_apply) lemma foldr_fold: assumes "\<And>x y. x \<in> set xs \<Longrightarrow> y \<in> set xs \<Longrightarrow> f y \<circ> f x = f x \<circ> f y" shows "foldr f xs = fold f xs" using assms unfolding foldr_fold_rev by (rule fold_rev) lemma fold_Cons_rev: "fold Cons xs = append (rev xs)" by (induct xs) simp_all lemma rev_conv_fold [code]: "rev xs = fold Cons xs []" by (simp add: fold_Cons_rev) lemma fold_append_concat_rev: "fold append xss = append (concat (rev xss))" by (induct xss) simp_all lemma concat_conv_foldr [code]: "concat xss = foldr append xss []" by (simp add: fold_append_concat_rev foldr_fold_rev) lemma fold_plus_listsum_rev: "fold plus xs = plus (listsum (rev xs))" by (induct xs) (simp_all add: add.assoc) lemma listsum_conv_foldr [code]: "listsum xs = foldr plus xs 0" by (fact listsum_foldr) lemma sort_key_conv_fold: assumes "inj_on f (set xs)" shows "sort_key f xs = fold (insort_key f) xs []" proof - have "fold (insort_key f) (rev xs) = fold (insort_key f) xs" proof (rule fold_rev, rule ext) fix zs fix x y assume "x \<in> set xs" "y \<in> set xs" with assms have *: "f y = f x \<Longrightarrow> y = x" by (auto dest: inj_onD) show "(insort_key f y \<circ> insort_key f x) zs = (insort_key f x \<circ> insort_key f y) zs" by (induct zs) (auto dest: *) qed then show ?thesis by (simp add: sort_key_def foldr_fold_rev) qed lemma sort_conv_fold: "sort xs = fold insort xs []" by (rule sort_key_conv_fold) simp text {* @{const Finite_Set.fold} and @{const fold} *} lemma (in fun_left_comm) fold_set_remdups: "Finite_Set.fold f y (set xs) = fold f (remdups xs) y" by (rule sym, induct xs arbitrary: y) (simp_all add: fold_fun_comm insert_absorb) lemma (in fun_left_comm_idem) fold_set: "Finite_Set.fold f y (set xs) = fold f xs y" by (rule sym, induct xs arbitrary: y) (simp_all add: fold_fun_comm) lemma (in ab_semigroup_idem_mult) fold1_set: assumes "xs \<noteq> []" shows "Finite_Set.fold1 times (set xs) = fold times (tl xs) (hd xs)" proof - interpret fun_left_comm_idem times by (fact fun_left_comm_idem) from assms obtain y ys where xs: "xs = y # ys" by (cases xs) auto show ?thesis proof (cases "set ys = {}") case True with xs show ?thesis by simp next case False then have "fold1 times (insert y (set ys)) = Finite_Set.fold times y (set ys)" by (simp only: finite_set fold1_eq_fold_idem) with xs show ?thesis by (simp add: fold_set mult_commute) qed qed lemma (in lattice) Inf_fin_set_fold: "Inf_fin (set (x # xs)) = fold inf xs x" proof - interpret ab_semigroup_idem_mult "inf :: 'a \<Rightarrow> 'a \<Rightarrow> 'a" by (fact ab_semigroup_idem_mult_inf) show ?thesis by (simp add: Inf_fin_def fold1_set del: set.simps) qed lemma (in lattice) Inf_fin_set_foldr [code_unfold]: "Inf_fin (set (x # xs)) = foldr inf xs x" by (simp add: Inf_fin_set_fold ac_simps foldr_fold expand_fun_eq del: set.simps) lemma (in lattice) Sup_fin_set_fold: "Sup_fin (set (x # xs)) = fold sup xs x" proof - interpret ab_semigroup_idem_mult "sup :: 'a \<Rightarrow> 'a \<Rightarrow> 'a" by (fact ab_semigroup_idem_mult_sup) show ?thesis by (simp add: Sup_fin_def fold1_set del: set.simps) qed lemma (in lattice) Sup_fin_set_foldr [code_unfold]: "Sup_fin (set (x # xs)) = foldr sup xs x" by (simp add: Sup_fin_set_fold ac_simps foldr_fold expand_fun_eq del: set.simps) lemma (in linorder) Min_fin_set_fold: "Min (set (x # xs)) = fold min xs x" proof - interpret ab_semigroup_idem_mult "min :: 'a \<Rightarrow> 'a \<Rightarrow> 'a" by (fact ab_semigroup_idem_mult_min) show ?thesis by (simp add: Min_def fold1_set del: set.simps) qed lemma (in linorder) Min_fin_set_foldr [code_unfold]: "Min (set (x # xs)) = foldr min xs x" by (simp add: Min_fin_set_fold ac_simps foldr_fold expand_fun_eq del: set.simps) lemma (in linorder) Max_fin_set_fold: "Max (set (x # xs)) = fold max xs x" proof - interpret ab_semigroup_idem_mult "max :: 'a \<Rightarrow> 'a \<Rightarrow> 'a" by (fact ab_semigroup_idem_mult_max) show ?thesis by (simp add: Max_def fold1_set del: set.simps) qed lemma (in linorder) Max_fin_set_foldr [code_unfold]: "Max (set (x # xs)) = foldr max xs x" by (simp add: Max_fin_set_fold ac_simps foldr_fold expand_fun_eq del: set.simps) lemma (in complete_lattice) Inf_set_fold: "Inf (set xs) = fold inf xs top" proof - interpret fun_left_comm_idem "inf :: 'a \<Rightarrow> 'a \<Rightarrow> 'a" by (fact fun_left_comm_idem_inf) show ?thesis by (simp add: Inf_fold_inf fold_set inf_commute) qed lemma (in complete_lattice) Inf_set_foldr [code_unfold]: "Inf (set xs) = foldr inf xs top" by (simp add: Inf_set_fold ac_simps foldr_fold expand_fun_eq) lemma (in complete_lattice) Sup_set_fold: "Sup (set xs) = fold sup xs bot" proof - interpret fun_left_comm_idem "sup :: 'a \<Rightarrow> 'a \<Rightarrow> 'a" by (fact fun_left_comm_idem_sup) show ?thesis by (simp add: Sup_fold_sup fold_set sup_commute) qed lemma (in complete_lattice) Sup_set_foldr [code_unfold]: "Sup (set xs) = foldr sup xs bot" by (simp add: Sup_set_fold ac_simps foldr_fold expand_fun_eq) lemma (in complete_lattice) INFI_set_fold: "INFI (set xs) f = fold (inf \<circ> f) xs top" unfolding INFI_def set_map [symmetric] Inf_set_fold fold_map .. lemma (in complete_lattice) SUPR_set_fold: "SUPR (set xs) f = fold (sup \<circ> f) xs bot" unfolding SUPR_def set_map [symmetric] Sup_set_fold fold_map .. text {* @{text nth_map} *} definition nth_map :: "nat \<Rightarrow> ('a \<Rightarrow> 'a) \<Rightarrow> 'a list \<Rightarrow> 'a list" where "nth_map n f xs = (if n < length xs then take n xs @ [f (xs ! n)] @ drop (Suc n) xs else xs)" lemma nth_map_id: "n \<ge> length xs \<Longrightarrow> nth_map n f xs = xs" by (simp add: nth_map_def) lemma nth_map_unfold: "n < length xs \<Longrightarrow> nth_map n f xs = take n xs @ [f (xs ! n)] @ drop (Suc n) xs" by (simp add: nth_map_def) lemma nth_map_Nil [simp]: "nth_map n f [] = []" by (simp add: nth_map_def) lemma nth_map_zero [simp]: "nth_map 0 f (x # xs) = f x # xs" by (simp add: nth_map_def) lemma nth_map_Suc [simp]: "nth_map (Suc n) f (x # xs) = x # nth_map n f xs" by (simp add: nth_map_def) end