(* Title: HOL/Finite_Set.thy
Author: Tobias Nipkow, Lawrence C Paulson and Markus Wenzel
with contributions by Jeremy Avigad
*)
header {* Finite sets *}
theory Finite_Set
imports Power Option
begin
subsection {* Definition and basic properties *}
inductive finite :: "'a set => bool"
where
emptyI [simp, intro!]: "finite {}"
| insertI [simp, intro!]: "finite A ==> finite (insert a A)"
lemma ex_new_if_finite: -- "does not depend on def of finite at all"
assumes "\<not> finite (UNIV :: 'a set)" and "finite A"
shows "\<exists>a::'a. a \<notin> A"
proof -
from assms have "A \<noteq> UNIV" by blast
thus ?thesis by blast
qed
lemma finite_induct [case_names empty insert, induct set: finite]:
"finite F ==>
P {} ==> (!!x F. finite F ==> x \<notin> F ==> P F ==> P (insert x F)) ==> P F"
-- {* Discharging @{text "x \<notin> F"} entails extra work. *}
proof -
assume "P {}" and
insert: "!!x F. finite F ==> x \<notin> F ==> P F ==> P (insert x F)"
assume "finite F"
thus "P F"
proof induct
show "P {}" by fact
fix x F assume F: "finite F" and P: "P F"
show "P (insert x F)"
proof cases
assume "x \<in> F"
hence "insert x F = F" by (rule insert_absorb)
with P show ?thesis by (simp only:)
next
assume "x \<notin> F"
from F this P show ?thesis by (rule insert)
qed
qed
qed
lemma finite_ne_induct[case_names singleton insert, consumes 2]:
assumes fin: "finite F" shows "F \<noteq> {} \<Longrightarrow>
\<lbrakk> \<And>x. P{x};
\<And>x F. \<lbrakk> finite F; F \<noteq> {}; x \<notin> F; P F \<rbrakk> \<Longrightarrow> P (insert x F) \<rbrakk>
\<Longrightarrow> P F"
using fin
proof induct
case empty thus ?case by simp
next
case (insert x F)
show ?case
proof cases
assume "F = {}"
thus ?thesis using `P {x}` by simp
next
assume "F \<noteq> {}"
thus ?thesis using insert by blast
qed
qed
lemma finite_subset_induct [consumes 2, case_names empty insert]:
assumes "finite F" and "F \<subseteq> A"
and empty: "P {}"
and insert: "!!a F. finite F ==> a \<in> A ==> a \<notin> F ==> P F ==> P (insert a F)"
shows "P F"
proof -
from `finite F` and `F \<subseteq> A`
show ?thesis
proof induct
show "P {}" by fact
next
fix x F
assume "finite F" and "x \<notin> F" and
P: "F \<subseteq> A ==> P F" and i: "insert x F \<subseteq> A"
show "P (insert x F)"
proof (rule insert)
from i show "x \<in> A" by blast
from i have "F \<subseteq> A" by blast
with P show "P F" .
show "finite F" by fact
show "x \<notin> F" by fact
qed
qed
qed
text{* A finite choice principle. Does not need the SOME choice operator. *}
lemma finite_set_choice:
"finite A \<Longrightarrow> ALL x:A. (EX y. P x y) \<Longrightarrow> EX f. ALL x:A. P x (f x)"
proof (induct set: finite)
case empty thus ?case by simp
next
case (insert a A)
then obtain f b where f: "ALL x:A. P x (f x)" and ab: "P a b" by auto
show ?case (is "EX f. ?P f")
proof
show "?P(%x. if x = a then b else f x)" using f ab by auto
qed
qed
text{* Finite sets are the images of initial segments of natural numbers: *}
lemma finite_imp_nat_seg_image_inj_on:
assumes fin: "finite A"
shows "\<exists> (n::nat) f. A = f ` {i. i<n} & inj_on f {i. i<n}"
using fin
proof induct
case empty
show ?case
proof show "\<exists>f. {} = f ` {i::nat. i < 0} & inj_on f {i. i<0}" by simp
qed
next
case (insert a A)
have notinA: "a \<notin> A" by fact
from insert.hyps obtain n f
where "A = f ` {i::nat. i < n}" "inj_on f {i. i < n}" by blast
hence "insert a A = f(n:=a) ` {i. i < Suc n}"
"inj_on (f(n:=a)) {i. i < Suc n}" using notinA
by (auto simp add: image_def Ball_def inj_on_def less_Suc_eq)
thus ?case by blast
qed
lemma nat_seg_image_imp_finite:
"!!f A. A = f ` {i::nat. i<n} \<Longrightarrow> finite A"
proof (induct n)
case 0 thus ?case by simp
next
case (Suc n)
let ?B = "f ` {i. i < n}"
have finB: "finite ?B" by(rule Suc.hyps[OF refl])
show ?case
proof cases
assume "\<exists>k<n. f n = f k"
hence "A = ?B" using Suc.prems by(auto simp:less_Suc_eq)
thus ?thesis using finB by simp
next
assume "\<not>(\<exists> k<n. f n = f k)"
hence "A = insert (f n) ?B" using Suc.prems by(auto simp:less_Suc_eq)
thus ?thesis using finB by simp
qed
qed
lemma finite_conv_nat_seg_image:
"finite A = (\<exists> (n::nat) f. A = f ` {i::nat. i<n})"
by(blast intro: nat_seg_image_imp_finite dest: finite_imp_nat_seg_image_inj_on)
lemma finite_imp_inj_to_nat_seg:
assumes "finite A"
shows "EX f n::nat. f`A = {i. i<n} & inj_on f A"
proof -
from finite_imp_nat_seg_image_inj_on[OF `finite A`]
obtain f and n::nat where bij: "bij_betw f {i. i<n} A"
by (auto simp:bij_betw_def)
let ?f = "the_inv_into {i. i<n} f"
have "inj_on ?f A & ?f ` A = {i. i<n}"
by (fold bij_betw_def) (rule bij_betw_the_inv_into[OF bij])
thus ?thesis by blast
qed
lemma finite_Collect_less_nat[iff]: "finite{n::nat. n<k}"
by(fastsimp simp: finite_conv_nat_seg_image)
subsubsection{* Finiteness and set theoretic constructions *}
lemma finite_UnI: "finite F ==> finite G ==> finite (F Un G)"
by (induct set: finite) simp_all
lemma finite_subset: "A \<subseteq> B ==> finite B ==> finite A"
-- {* Every subset of a finite set is finite. *}
proof -
assume "finite B"
thus "!!A. A \<subseteq> B ==> finite A"
proof induct
case empty
thus ?case by simp
next
case (insert x F A)
have A: "A \<subseteq> insert x F" and r: "A - {x} \<subseteq> F ==> finite (A - {x})" by fact+
show "finite A"
proof cases
assume x: "x \<in> A"
with A have "A - {x} \<subseteq> F" by (simp add: subset_insert_iff)
with r have "finite (A - {x})" .
hence "finite (insert x (A - {x}))" ..
also have "insert x (A - {x}) = A" using x by (rule insert_Diff)
finally show ?thesis .
next
show "A \<subseteq> F ==> ?thesis" by fact
assume "x \<notin> A"
with A show "A \<subseteq> F" by (simp add: subset_insert_iff)
qed
qed
qed
lemma rev_finite_subset: "finite B ==> A \<subseteq> B ==> finite A"
by (rule finite_subset)
lemma finite_Un [iff]: "finite (F Un G) = (finite F & finite G)"
by (blast intro: finite_subset [of _ "X Un Y", standard] finite_UnI)
lemma finite_Collect_disjI[simp]:
"finite{x. P x | Q x} = (finite{x. P x} & finite{x. Q x})"
by(simp add:Collect_disj_eq)
lemma finite_Int [simp, intro]: "finite F | finite G ==> finite (F Int G)"
-- {* The converse obviously fails. *}
by (blast intro: finite_subset)
lemma finite_Collect_conjI [simp, intro]:
"finite{x. P x} | finite{x. Q x} ==> finite{x. P x & Q x}"
-- {* The converse obviously fails. *}
by(simp add:Collect_conj_eq)
lemma finite_Collect_le_nat[iff]: "finite{n::nat. n<=k}"
by(simp add: le_eq_less_or_eq)
lemma finite_insert [simp]: "finite (insert a A) = finite A"
apply (subst insert_is_Un)
apply (simp only: finite_Un, blast)
done
lemma finite_Union[simp, intro]:
"\<lbrakk> finite A; !!M. M \<in> A \<Longrightarrow> finite M \<rbrakk> \<Longrightarrow> finite(\<Union>A)"
by (induct rule:finite_induct) simp_all
lemma finite_Inter[intro]: "EX A:M. finite(A) \<Longrightarrow> finite(Inter M)"
by (blast intro: Inter_lower finite_subset)
lemma finite_INT[intro]: "EX x:I. finite(A x) \<Longrightarrow> finite(INT x:I. A x)"
by (blast intro: INT_lower finite_subset)
lemma finite_empty_induct:
assumes "finite A"
and "P A"
and "!!a A. finite A ==> a:A ==> P A ==> P (A - {a})"
shows "P {}"
proof -
have "P (A - A)"
proof -
{
fix c b :: "'a set"
assume c: "finite c" and b: "finite b"
and P1: "P b" and P2: "!!x y. finite y ==> x \<in> y ==> P y ==> P (y - {x})"
have "c \<subseteq> b ==> P (b - c)"
using c
proof induct
case empty
from P1 show ?case by simp
next
case (insert x F)
have "P (b - F - {x})"
proof (rule P2)
from _ b show "finite (b - F)" by (rule finite_subset) blast
from insert show "x \<in> b - F" by simp
from insert show "P (b - F)" by simp
qed
also have "b - F - {x} = b - insert x F" by (rule Diff_insert [symmetric])
finally show ?case .
qed
}
then show ?thesis by this (simp_all add: assms)
qed
then show ?thesis by simp
qed
lemma finite_Diff [simp]: "finite A ==> finite (A - B)"
by (rule Diff_subset [THEN finite_subset])
lemma finite_Diff2 [simp]:
assumes "finite B" shows "finite (A - B) = finite A"
proof -
have "finite A \<longleftrightarrow> finite((A-B) Un (A Int B))" by(simp add: Un_Diff_Int)
also have "\<dots> \<longleftrightarrow> finite(A-B)" using `finite B` by(simp)
finally show ?thesis ..
qed
lemma finite_compl[simp]:
"finite(A::'a set) \<Longrightarrow> finite(-A) = finite(UNIV::'a set)"
by(simp add:Compl_eq_Diff_UNIV)
lemma finite_Collect_not[simp]:
"finite{x::'a. P x} \<Longrightarrow> finite{x. ~P x} = finite(UNIV::'a set)"
by(simp add:Collect_neg_eq)
lemma finite_Diff_insert [iff]: "finite (A - insert a B) = finite (A - B)"
apply (subst Diff_insert)
apply (case_tac "a : A - B")
apply (rule finite_insert [symmetric, THEN trans])
apply (subst insert_Diff, simp_all)
done
text {* Image and Inverse Image over Finite Sets *}
lemma finite_imageI[simp]: "finite F ==> finite (h ` F)"
-- {* The image of a finite set is finite. *}
by (induct set: finite) simp_all
lemma finite_image_set [simp]:
"finite {x. P x} \<Longrightarrow> finite { f x | x. P x }"
by (simp add: image_Collect [symmetric])
lemma finite_surj: "finite A ==> B <= f ` A ==> finite B"
apply (frule finite_imageI)
apply (erule finite_subset, assumption)
done
lemma finite_range_imageI:
"finite (range g) ==> finite (range (%x. f (g x)))"
apply (drule finite_imageI, simp add: range_composition)
done
lemma finite_imageD: "finite (f`A) ==> inj_on f A ==> finite A"
proof -
have aux: "!!A. finite (A - {}) = finite A" by simp
fix B :: "'a set"
assume "finite B"
thus "!!A. f`A = B ==> inj_on f A ==> finite A"
apply induct
apply simp
apply (subgoal_tac "EX y:A. f y = x & F = f ` (A - {y})")
apply clarify
apply (simp (no_asm_use) add: inj_on_def)
apply (blast dest!: aux [THEN iffD1], atomize)
apply (erule_tac V = "ALL A. ?PP (A)" in thin_rl)
apply (frule subsetD [OF equalityD2 insertI1], clarify)
apply (rule_tac x = xa in bexI)
apply (simp_all add: inj_on_image_set_diff)
done
qed (rule refl)
lemma inj_vimage_singleton: "inj f ==> f-`{a} \<subseteq> {THE x. f x = a}"
-- {* The inverse image of a singleton under an injective function
is included in a singleton. *}
apply (auto simp add: inj_on_def)
apply (blast intro: the_equality [symmetric])
done
lemma finite_vimageI: "[|finite F; inj h|] ==> finite (h -` F)"
-- {* The inverse image of a finite set under an injective function
is finite. *}
apply (induct set: finite)
apply simp_all
apply (subst vimage_insert)
apply (simp add: finite_subset [OF inj_vimage_singleton])
done
lemma finite_vimageD:
assumes fin: "finite (h -` F)" and surj: "surj h"
shows "finite F"
proof -
have "finite (h ` (h -` F))" using fin by (rule finite_imageI)
also have "h ` (h -` F) = F" using surj by (rule surj_image_vimage_eq)
finally show "finite F" .
qed
lemma finite_vimage_iff: "bij h \<Longrightarrow> finite (h -` F) \<longleftrightarrow> finite F"
unfolding bij_def by (auto elim: finite_vimageD finite_vimageI)
text {* The finite UNION of finite sets *}
lemma finite_UN_I: "finite A ==> (!!a. a:A ==> finite (B a)) ==> finite (UN a:A. B a)"
by (induct set: finite) simp_all
text {*
Strengthen RHS to
@{prop "((ALL x:A. finite (B x)) & finite {x. x:A & B x \<noteq> {}})"}?
We'd need to prove
@{prop "finite C ==> ALL A B. (UNION A B) <= C --> finite {x. x:A & B x \<noteq> {}}"}
by induction. *}
lemma finite_UN [simp]:
"finite A ==> finite (UNION A B) = (ALL x:A. finite (B x))"
by (blast intro: finite_UN_I finite_subset)
lemma finite_Collect_bex[simp]: "finite A \<Longrightarrow>
finite{x. EX y:A. Q x y} = (ALL y:A. finite{x. Q x y})"
apply(subgoal_tac "{x. EX y:A. Q x y} = UNION A (%y. {x. Q x y})")
apply auto
done
lemma finite_Collect_bounded_ex[simp]: "finite{y. P y} \<Longrightarrow>
finite{x. EX y. P y & Q x y} = (ALL y. P y \<longrightarrow> finite{x. Q x y})"
apply(subgoal_tac "{x. EX y. P y & Q x y} = UNION {y. P y} (%y. {x. Q x y})")
apply auto
done
lemma finite_Plus: "[| finite A; finite B |] ==> finite (A <+> B)"
by (simp add: Plus_def)
lemma finite_PlusD:
fixes A :: "'a set" and B :: "'b set"
assumes fin: "finite (A <+> B)"
shows "finite A" "finite B"
proof -
have "Inl ` A \<subseteq> A <+> B" by auto
hence "finite (Inl ` A :: ('a + 'b) set)" using fin by(rule finite_subset)
thus "finite A" by(rule finite_imageD)(auto intro: inj_onI)
next
have "Inr ` B \<subseteq> A <+> B" by auto
hence "finite (Inr ` B :: ('a + 'b) set)" using fin by(rule finite_subset)
thus "finite B" by(rule finite_imageD)(auto intro: inj_onI)
qed
lemma finite_Plus_iff[simp]: "finite (A <+> B) \<longleftrightarrow> finite A \<and> finite B"
by(auto intro: finite_PlusD finite_Plus)
lemma finite_Plus_UNIV_iff[simp]:
"finite (UNIV :: ('a + 'b) set) =
(finite (UNIV :: 'a set) & finite (UNIV :: 'b set))"
by(subst UNIV_Plus_UNIV[symmetric])(rule finite_Plus_iff)
text {* Sigma of finite sets *}
lemma finite_SigmaI [simp]:
"finite A ==> (!!a. a:A ==> finite (B a)) ==> finite (SIGMA a:A. B a)"
by (unfold Sigma_def) (blast intro!: finite_UN_I)
lemma finite_cartesian_product: "[| finite A; finite B |] ==>
finite (A <*> B)"
by (rule finite_SigmaI)
lemma finite_Prod_UNIV:
"finite (UNIV::'a set) ==> finite (UNIV::'b set) ==> finite (UNIV::('a * 'b) set)"
apply (subgoal_tac "(UNIV:: ('a * 'b) set) = Sigma UNIV (%x. UNIV)")
apply (erule ssubst)
apply (erule finite_SigmaI, auto)
done
lemma finite_cartesian_productD1:
"[| finite (A <*> B); B \<noteq> {} |] ==> finite A"
apply (auto simp add: finite_conv_nat_seg_image)
apply (drule_tac x=n in spec)
apply (drule_tac x="fst o f" in spec)
apply (auto simp add: o_def)
prefer 2 apply (force dest!: equalityD2)
apply (drule equalityD1)
apply (rename_tac y x)
apply (subgoal_tac "\<exists>k. k<n & f k = (x,y)")
prefer 2 apply force
apply clarify
apply (rule_tac x=k in image_eqI, auto)
done
lemma finite_cartesian_productD2:
"[| finite (A <*> B); A \<noteq> {} |] ==> finite B"
apply (auto simp add: finite_conv_nat_seg_image)
apply (drule_tac x=n in spec)
apply (drule_tac x="snd o f" in spec)
apply (auto simp add: o_def)
prefer 2 apply (force dest!: equalityD2)
apply (drule equalityD1)
apply (rename_tac x y)
apply (subgoal_tac "\<exists>k. k<n & f k = (x,y)")
prefer 2 apply force
apply clarify
apply (rule_tac x=k in image_eqI, auto)
done
text {* The powerset of a finite set *}
lemma finite_Pow_iff [iff]: "finite (Pow A) = finite A"
proof
assume "finite (Pow A)"
with _ have "finite ((%x. {x}) ` A)" by (rule finite_subset) blast
thus "finite A" by (rule finite_imageD [unfolded inj_on_def]) simp
next
assume "finite A"
thus "finite (Pow A)"
by induct (simp_all add: Pow_insert)
qed
lemma finite_Collect_subsets[simp,intro]: "finite A \<Longrightarrow> finite{B. B \<subseteq> A}"
by(simp add: Pow_def[symmetric])
lemma finite_UnionD: "finite(\<Union>A) \<Longrightarrow> finite A"
by(blast intro: finite_subset[OF subset_Pow_Union])
lemma finite_subset_image:
assumes "finite B"
shows "B \<subseteq> f ` A \<Longrightarrow> \<exists>C\<subseteq>A. finite C \<and> B = f ` C"
using assms proof(induct)
case empty thus ?case by simp
next
case insert thus ?case
by (clarsimp simp del: image_insert simp add: image_insert[symmetric])
blast
qed
subsection {* Class @{text finite} *}
setup {* Sign.add_path "finite" *} -- {*FIXME: name tweaking*}
class finite =
assumes finite_UNIV: "finite (UNIV \<Colon> 'a set)"
setup {* Sign.parent_path *}
hide const finite
context finite
begin
lemma finite [simp]: "finite (A \<Colon> 'a set)"
by (rule subset_UNIV finite_UNIV finite_subset)+
end
lemma UNIV_unit [noatp]:
"UNIV = {()}" by auto
instance unit :: finite proof
qed (simp add: UNIV_unit)
lemma UNIV_bool [noatp]:
"UNIV = {False, True}" by auto
instance bool :: finite proof
qed (simp add: UNIV_bool)
instance * :: (finite, finite) finite proof
qed (simp only: UNIV_Times_UNIV [symmetric] finite_cartesian_product finite)
lemma finite_option_UNIV [simp]:
"finite (UNIV :: 'a option set) = finite (UNIV :: 'a set)"
by (auto simp add: UNIV_option_conv elim: finite_imageD intro: inj_Some)
instance option :: (finite) finite proof
qed (simp add: UNIV_option_conv)
lemma inj_graph: "inj (%f. {(x, y). y = f x})"
by (rule inj_onI, auto simp add: expand_set_eq expand_fun_eq)
instance "fun" :: (finite, finite) finite
proof
show "finite (UNIV :: ('a => 'b) set)"
proof (rule finite_imageD)
let ?graph = "%f::'a => 'b. {(x, y). y = f x}"
have "range ?graph \<subseteq> Pow UNIV" by simp
moreover have "finite (Pow (UNIV :: ('a * 'b) set))"
by (simp only: finite_Pow_iff finite)
ultimately show "finite (range ?graph)"
by (rule finite_subset)
show "inj ?graph" by (rule inj_graph)
qed
qed
instance "+" :: (finite, finite) finite proof
qed (simp only: UNIV_Plus_UNIV [symmetric] finite_Plus finite)
subsection {* A fold functional for finite sets *}
text {* The intended behaviour is
@{text "fold f z {x\<^isub>1, ..., x\<^isub>n} = f x\<^isub>1 (\<dots> (f x\<^isub>n z)\<dots>)"}
if @{text f} is ``left-commutative'':
*}
locale fun_left_comm =
fixes f :: "'a \<Rightarrow> 'b \<Rightarrow> 'b"
assumes fun_left_comm: "f x (f y z) = f y (f x z)"
begin
text{* On a functional level it looks much nicer: *}
lemma fun_comp_comm: "f x \<circ> f y = f y \<circ> f x"
by (simp add: fun_left_comm expand_fun_eq)
end
inductive fold_graph :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a set \<Rightarrow> 'b \<Rightarrow> bool"
for f :: "'a \<Rightarrow> 'b \<Rightarrow> 'b" and z :: 'b where
emptyI [intro]: "fold_graph f z {} z" |
insertI [intro]: "x \<notin> A \<Longrightarrow> fold_graph f z A y
\<Longrightarrow> fold_graph f z (insert x A) (f x y)"
inductive_cases empty_fold_graphE [elim!]: "fold_graph f z {} x"
definition fold :: "('a \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a set \<Rightarrow> 'b" where
[code del]: "fold f z A = (THE y. fold_graph f z A y)"
text{*A tempting alternative for the definiens is
@{term "if finite A then THE y. fold_graph f z A y else e"}.
It allows the removal of finiteness assumptions from the theorems
@{text fold_comm}, @{text fold_reindex} and @{text fold_distrib}.
The proofs become ugly. It is not worth the effort. (???) *}
lemma Diff1_fold_graph:
"fold_graph f z (A - {x}) y \<Longrightarrow> x \<in> A \<Longrightarrow> fold_graph f z A (f x y)"
by (erule insert_Diff [THEN subst], rule fold_graph.intros, auto)
lemma fold_graph_imp_finite: "fold_graph f z A x \<Longrightarrow> finite A"
by (induct set: fold_graph) auto
lemma finite_imp_fold_graph: "finite A \<Longrightarrow> \<exists>x. fold_graph f z A x"
by (induct set: finite) auto
subsubsection{*From @{const fold_graph} to @{term fold}*}
lemma image_less_Suc: "h ` {i. i < Suc m} = insert (h m) (h ` {i. i < m})"
by (auto simp add: less_Suc_eq)
lemma insert_image_inj_on_eq:
"[|insert (h m) A = h ` {i. i < Suc m}; h m \<notin> A;
inj_on h {i. i < Suc m}|]
==> A = h ` {i. i < m}"
apply (auto simp add: image_less_Suc inj_on_def)
apply (blast intro: less_trans)
done
lemma insert_inj_onE:
assumes aA: "insert a A = h`{i::nat. i<n}" and anot: "a \<notin> A"
and inj_on: "inj_on h {i::nat. i<n}"
shows "\<exists>hm m. inj_on hm {i::nat. i<m} & A = hm ` {i. i<m} & m < n"
proof (cases n)
case 0 thus ?thesis using aA by auto
next
case (Suc m)
have nSuc: "n = Suc m" by fact
have mlessn: "m<n" by (simp add: nSuc)
from aA obtain k where hkeq: "h k = a" and klessn: "k<n" by (blast elim!: equalityE)
let ?hm = "Fun.swap k m h"
have inj_hm: "inj_on ?hm {i. i < n}" using klessn mlessn
by (simp add: inj_on)
show ?thesis
proof (intro exI conjI)
show "inj_on ?hm {i. i < m}" using inj_hm
by (auto simp add: nSuc less_Suc_eq intro: subset_inj_on)
show "m<n" by (rule mlessn)
show "A = ?hm ` {i. i < m}"
proof (rule insert_image_inj_on_eq)
show "inj_on (Fun.swap k m h) {i. i < Suc m}" using inj_hm nSuc by simp
show "?hm m \<notin> A" by (simp add: swap_def hkeq anot)
show "insert (?hm m) A = ?hm ` {i. i < Suc m}"
using aA hkeq nSuc klessn
by (auto simp add: swap_def image_less_Suc fun_upd_image
less_Suc_eq inj_on_image_set_diff [OF inj_on])
qed
qed
qed
context fun_left_comm
begin
lemma fold_graph_determ_aux:
"A = h`{i::nat. i<n} \<Longrightarrow> inj_on h {i. i<n}
\<Longrightarrow> fold_graph f z A x \<Longrightarrow> fold_graph f z A x'
\<Longrightarrow> x' = x"
proof (induct n arbitrary: A x x' h rule: less_induct)
case (less n)
have IH: "\<And>m h A x x'. m < n \<Longrightarrow> A = h ` {i. i<m}
\<Longrightarrow> inj_on h {i. i<m} \<Longrightarrow> fold_graph f z A x
\<Longrightarrow> fold_graph f z A x' \<Longrightarrow> x' = x" by fact
have Afoldx: "fold_graph f z A x" and Afoldx': "fold_graph f z A x'"
and A: "A = h`{i. i<n}" and injh: "inj_on h {i. i<n}" by fact+
show ?case
proof (rule fold_graph.cases [OF Afoldx])
assume "A = {}" and "x = z"
with Afoldx' show "x' = x" by auto
next
fix B b u
assume AbB: "A = insert b B" and x: "x = f b u"
and notinB: "b \<notin> B" and Bu: "fold_graph f z B u"
show "x'=x"
proof (rule fold_graph.cases [OF Afoldx'])
assume "A = {}" and "x' = z"
with AbB show "x' = x" by blast
next
fix C c v
assume AcC: "A = insert c C" and x': "x' = f c v"
and notinC: "c \<notin> C" and Cv: "fold_graph f z C v"
from A AbB have Beq: "insert b B = h`{i. i<n}" by simp
from insert_inj_onE [OF Beq notinB injh]
obtain hB mB where inj_onB: "inj_on hB {i. i < mB}"
and Beq: "B = hB ` {i. i < mB}" and lessB: "mB < n" by auto
from A AcC have Ceq: "insert c C = h`{i. i<n}" by simp
from insert_inj_onE [OF Ceq notinC injh]
obtain hC mC where inj_onC: "inj_on hC {i. i < mC}"
and Ceq: "C = hC ` {i. i < mC}" and lessC: "mC < n" by auto
show "x'=x"
proof cases
assume "b=c"
then moreover have "B = C" using AbB AcC notinB notinC by auto
ultimately show ?thesis using Bu Cv x x' IH [OF lessC Ceq inj_onC]
by auto
next
assume diff: "b \<noteq> c"
let ?D = "B - {c}"
have B: "B = insert c ?D" and C: "C = insert b ?D"
using AbB AcC notinB notinC diff by(blast elim!:equalityE)+
have "finite A" by(rule fold_graph_imp_finite [OF Afoldx])
with AbB have "finite ?D" by simp
then obtain d where Dfoldd: "fold_graph f z ?D d"
using finite_imp_fold_graph by iprover
moreover have cinB: "c \<in> B" using B by auto
ultimately have "fold_graph f z B (f c d)" by(rule Diff1_fold_graph)
hence "f c d = u" by (rule IH [OF lessB Beq inj_onB Bu])
moreover have "f b d = v"
proof (rule IH[OF lessC Ceq inj_onC Cv])
show "fold_graph f z C (f b d)" using C notinB Dfoldd by fastsimp
qed
ultimately show ?thesis
using fun_left_comm [of c b] x x' by (auto simp add: o_def)
qed
qed
qed
qed
lemma fold_graph_determ:
"fold_graph f z A x \<Longrightarrow> fold_graph f z A y \<Longrightarrow> y = x"
apply (frule fold_graph_imp_finite [THEN finite_imp_nat_seg_image_inj_on])
apply (blast intro: fold_graph_determ_aux [rule_format])
done
lemma fold_equality:
"fold_graph f z A y \<Longrightarrow> fold f z A = y"
by (unfold fold_def) (blast intro: fold_graph_determ)
text{* The base case for @{text fold}: *}
lemma (in -) fold_empty [simp]: "fold f z {} = z"
by (unfold fold_def) blast
text{* The various recursion equations for @{const fold}: *}
lemma fold_insert_aux: "x \<notin> A
\<Longrightarrow> fold_graph f z (insert x A) v \<longleftrightarrow>
(\<exists>y. fold_graph f z A y \<and> v = f x y)"
apply auto
apply (rule_tac A1 = A and f1 = f in finite_imp_fold_graph [THEN exE])
apply (fastsimp dest: fold_graph_imp_finite)
apply (blast intro: fold_graph_determ)
done
lemma fold_insert [simp]:
"finite A ==> x \<notin> A ==> fold f z (insert x A) = f x (fold f z A)"
apply (simp add: fold_def fold_insert_aux)
apply (rule the_equality)
apply (auto intro: finite_imp_fold_graph
cong add: conj_cong simp add: fold_def[symmetric] fold_equality)
done
lemma fold_fun_comm:
"finite A \<Longrightarrow> f x (fold f z A) = fold f (f x z) A"
proof (induct rule: finite_induct)
case empty then show ?case by simp
next
case (insert y A) then show ?case
by (simp add: fun_left_comm[of x])
qed
lemma fold_insert2:
"finite A \<Longrightarrow> x \<notin> A \<Longrightarrow> fold f z (insert x A) = fold f (f x z) A"
by (simp add: fold_fun_comm)
lemma fold_rec:
assumes "finite A" and "x \<in> A"
shows "fold f z A = f x (fold f z (A - {x}))"
proof -
have A: "A = insert x (A - {x})" using `x \<in> A` by blast
then have "fold f z A = fold f z (insert x (A - {x}))" by simp
also have "\<dots> = f x (fold f z (A - {x}))"
by (rule fold_insert) (simp add: `finite A`)+
finally show ?thesis .
qed
lemma fold_insert_remove:
assumes "finite A"
shows "fold f z (insert x A) = f x (fold f z (A - {x}))"
proof -
from `finite A` have "finite (insert x A)" by auto
moreover have "x \<in> insert x A" by auto
ultimately have "fold f z (insert x A) = f x (fold f z (insert x A - {x}))"
by (rule fold_rec)
then show ?thesis by simp
qed
end
text{* A simplified version for idempotent functions: *}
locale fun_left_comm_idem = fun_left_comm +
assumes fun_left_idem: "f x (f x z) = f x z"
begin
text{* The nice version: *}
lemma fun_comp_idem : "f x o f x = f x"
by (simp add: fun_left_idem expand_fun_eq)
lemma fold_insert_idem:
assumes fin: "finite A"
shows "fold f z (insert x A) = f x (fold f z A)"
proof cases
assume "x \<in> A"
then obtain B where "A = insert x B" and "x \<notin> B" by (rule set_insert)
then show ?thesis using assms by (simp add:fun_left_idem)
next
assume "x \<notin> A" then show ?thesis using assms by simp
qed
declare fold_insert[simp del] fold_insert_idem[simp]
lemma fold_insert_idem2:
"finite A \<Longrightarrow> fold f z (insert x A) = fold f (f x z) A"
by(simp add:fold_fun_comm)
end
context ab_semigroup_idem_mult
begin
lemma fun_left_comm_idem: "fun_left_comm_idem(op *)"
apply unfold_locales
apply (rule mult_left_commute)
apply (rule mult_left_idem)
done
end
context semilattice_inf
begin
lemma ab_semigroup_idem_mult_inf: "ab_semigroup_idem_mult inf"
proof qed (rule inf_assoc inf_commute inf_idem)+
lemma fold_inf_insert[simp]: "finite A \<Longrightarrow> fold inf b (insert a A) = inf a (fold inf b A)"
by(rule fun_left_comm_idem.fold_insert_idem[OF ab_semigroup_idem_mult.fun_left_comm_idem[OF ab_semigroup_idem_mult_inf]])
lemma inf_le_fold_inf: "finite A \<Longrightarrow> ALL a:A. b \<le> a \<Longrightarrow> inf b c \<le> fold inf c A"
by (induct pred: finite) (auto intro: le_infI1)
lemma fold_inf_le_inf: "finite A \<Longrightarrow> a \<in> A \<Longrightarrow> fold inf b A \<le> inf a b"
proof(induct arbitrary: a pred:finite)
case empty thus ?case by simp
next
case (insert x A)
show ?case
proof cases
assume "A = {}" thus ?thesis using insert by simp
next
assume "A \<noteq> {}" thus ?thesis using insert by (auto intro: le_infI2)
qed
qed
end
context semilattice_sup
begin
lemma ab_semigroup_idem_mult_sup: "ab_semigroup_idem_mult sup"
by (rule semilattice_inf.ab_semigroup_idem_mult_inf)(rule dual_semilattice)
lemma fold_sup_insert[simp]: "finite A \<Longrightarrow> fold sup b (insert a A) = sup a (fold sup b A)"
by(rule semilattice_inf.fold_inf_insert)(rule dual_semilattice)
lemma fold_sup_le_sup: "finite A \<Longrightarrow> ALL a:A. a \<le> b \<Longrightarrow> fold sup c A \<le> sup b c"
by(rule semilattice_inf.inf_le_fold_inf)(rule dual_semilattice)
lemma sup_le_fold_sup: "finite A \<Longrightarrow> a \<in> A \<Longrightarrow> sup a b \<le> fold sup b A"
by(rule semilattice_inf.fold_inf_le_inf)(rule dual_semilattice)
end
subsubsection{* The derived combinator @{text fold_image} *}
definition fold_image :: "('b \<Rightarrow> 'b \<Rightarrow> 'b) \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> 'b \<Rightarrow> 'a set \<Rightarrow> 'b"
where "fold_image f g = fold (%x y. f (g x) y)"
lemma fold_image_empty[simp]: "fold_image f g z {} = z"
by(simp add:fold_image_def)
context ab_semigroup_mult
begin
lemma fold_image_insert[simp]:
assumes "finite A" and "a \<notin> A"
shows "fold_image times g z (insert a A) = g a * (fold_image times g z A)"
proof -
interpret I: fun_left_comm "%x y. (g x) * y"
by unfold_locales (simp add: mult_ac)
show ?thesis using assms by(simp add:fold_image_def)
qed
(*
lemma fold_commute:
"finite A ==> (!!z. x * (fold times g z A) = fold times g (x * z) A)"
apply (induct set: finite)
apply simp
apply (simp add: mult_left_commute [of x])
done
lemma fold_nest_Un_Int:
"finite A ==> finite B
==> fold times g (fold times g z B) A = fold times g (fold times g z (A Int B)) (A Un B)"
apply (induct set: finite)
apply simp
apply (simp add: fold_commute Int_insert_left insert_absorb)
done
lemma fold_nest_Un_disjoint:
"finite A ==> finite B ==> A Int B = {}
==> fold times g z (A Un B) = fold times g (fold times g z B) A"
by (simp add: fold_nest_Un_Int)
*)
lemma fold_image_reindex:
assumes fin: "finite A"
shows "inj_on h A \<Longrightarrow> fold_image times g z (h`A) = fold_image times (g\<circ>h) z A"
using fin by induct auto
(*
text{*
Fusion theorem, as described in Graham Hutton's paper,
A Tutorial on the Universality and Expressiveness of Fold,
JFP 9:4 (355-372), 1999.
*}
lemma fold_fusion:
assumes "ab_semigroup_mult g"
assumes fin: "finite A"
and hyp: "\<And>x y. h (g x y) = times x (h y)"
shows "h (fold g j w A) = fold times j (h w) A"
proof -
class_interpret ab_semigroup_mult [g] by fact
show ?thesis using fin hyp by (induct set: finite) simp_all
qed
*)
lemma fold_image_cong:
"finite A \<Longrightarrow>
(!!x. x:A ==> g x = h x) ==> fold_image times g z A = fold_image times h z A"
apply (subgoal_tac "ALL C. C <= A --> (ALL x:C. g x = h x) --> fold_image times g z C = fold_image times h z C")
apply simp
apply (erule finite_induct, simp)
apply (simp add: subset_insert_iff, clarify)
apply (subgoal_tac "finite C")
prefer 2 apply (blast dest: finite_subset [COMP swap_prems_rl])
apply (subgoal_tac "C = insert x (C - {x})")
prefer 2 apply blast
apply (erule ssubst)
apply (drule spec)
apply (erule (1) notE impE)
apply (simp add: Ball_def del: insert_Diff_single)
done
end
context comm_monoid_mult
begin
lemma fold_image_Un_Int:
"finite A ==> finite B ==>
fold_image times g 1 A * fold_image times g 1 B =
fold_image times g 1 (A Un B) * fold_image times g 1 (A Int B)"
by (induct set: finite)
(auto simp add: mult_ac insert_absorb Int_insert_left)
corollary fold_Un_disjoint:
"finite A ==> finite B ==> A Int B = {} ==>
fold_image times g 1 (A Un B) =
fold_image times g 1 A * fold_image times g 1 B"
by (simp add: fold_image_Un_Int)
lemma fold_image_UN_disjoint:
"\<lbrakk> finite I; ALL i:I. finite (A i);
ALL i:I. ALL j:I. i \<noteq> j --> A i Int A j = {} \<rbrakk>
\<Longrightarrow> fold_image times g 1 (UNION I A) =
fold_image times (%i. fold_image times g 1 (A i)) 1 I"
apply (induct set: finite, simp, atomize)
apply (subgoal_tac "ALL i:F. x \<noteq> i")
prefer 2 apply blast
apply (subgoal_tac "A x Int UNION F A = {}")
prefer 2 apply blast
apply (simp add: fold_Un_disjoint)
done
lemma fold_image_Sigma: "finite A ==> ALL x:A. finite (B x) ==>
fold_image times (%x. fold_image times (g x) 1 (B x)) 1 A =
fold_image times (split g) 1 (SIGMA x:A. B x)"
apply (subst Sigma_def)
apply (subst fold_image_UN_disjoint, assumption, simp)
apply blast
apply (erule fold_image_cong)
apply (subst fold_image_UN_disjoint, simp, simp)
apply blast
apply simp
done
lemma fold_image_distrib: "finite A \<Longrightarrow>
fold_image times (%x. g x * h x) 1 A =
fold_image times g 1 A * fold_image times h 1 A"
by (erule finite_induct) (simp_all add: mult_ac)
lemma fold_image_related:
assumes Re: "R e e"
and Rop: "\<forall>x1 y1 x2 y2. R x1 x2 \<and> R y1 y2 \<longrightarrow> R (x1 * y1) (x2 * y2)"
and fS: "finite S" and Rfg: "\<forall>x\<in>S. R (h x) (g x)"
shows "R (fold_image (op *) h e S) (fold_image (op *) g e S)"
using fS by (rule finite_subset_induct) (insert assms, auto)
lemma fold_image_eq_general:
assumes fS: "finite S"
and h: "\<forall>y\<in>S'. \<exists>!x. x\<in> S \<and> h(x) = y"
and f12: "\<forall>x\<in>S. h x \<in> S' \<and> f2(h x) = f1 x"
shows "fold_image (op *) f1 e S = fold_image (op *) f2 e S'"
proof-
from h f12 have hS: "h ` S = S'" by auto
{fix x y assume H: "x \<in> S" "y \<in> S" "h x = h y"
from f12 h H have "x = y" by auto }
hence hinj: "inj_on h S" unfolding inj_on_def Ex1_def by blast
from f12 have th: "\<And>x. x \<in> S \<Longrightarrow> (f2 \<circ> h) x = f1 x" by auto
from hS have "fold_image (op *) f2 e S' = fold_image (op *) f2 e (h ` S)" by simp
also have "\<dots> = fold_image (op *) (f2 o h) e S"
using fold_image_reindex[OF fS hinj, of f2 e] .
also have "\<dots> = fold_image (op *) f1 e S " using th fold_image_cong[OF fS, of "f2 o h" f1 e]
by blast
finally show ?thesis ..
qed
lemma fold_image_eq_general_inverses:
assumes fS: "finite S"
and kh: "\<And>y. y \<in> T \<Longrightarrow> k y \<in> S \<and> h (k y) = y"
and hk: "\<And>x. x \<in> S \<Longrightarrow> h x \<in> T \<and> k (h x) = x \<and> g (h x) = f x"
shows "fold_image (op *) f e S = fold_image (op *) g e T"
(* metis solves it, but not yet available here *)
apply (rule fold_image_eq_general[OF fS, of T h g f e])
apply (rule ballI)
apply (frule kh)
apply (rule ex1I[])
apply blast
apply clarsimp
apply (drule hk) apply simp
apply (rule sym)
apply (erule conjunct1[OF conjunct2[OF hk]])
apply (rule ballI)
apply (drule hk)
apply blast
done
end
subsection{* A fold functional for non-empty sets *}
text{* Does not require start value. *}
inductive
fold1Set :: "('a => 'a => 'a) => 'a set => 'a => bool"
for f :: "'a => 'a => 'a"
where
fold1Set_insertI [intro]:
"\<lbrakk> fold_graph f a A x; a \<notin> A \<rbrakk> \<Longrightarrow> fold1Set f (insert a A) x"
definition fold1 :: "('a => 'a => 'a) => 'a set => 'a" where
"fold1 f A == THE x. fold1Set f A x"
lemma fold1Set_nonempty:
"fold1Set f A x \<Longrightarrow> A \<noteq> {}"
by(erule fold1Set.cases, simp_all)
inductive_cases empty_fold1SetE [elim!]: "fold1Set f {} x"
inductive_cases insert_fold1SetE [elim!]: "fold1Set f (insert a X) x"
lemma fold1Set_sing [iff]: "(fold1Set f {a} b) = (a = b)"
by (blast elim: fold_graph.cases)
lemma fold1_singleton [simp]: "fold1 f {a} = a"
by (unfold fold1_def) blast
lemma finite_nonempty_imp_fold1Set:
"\<lbrakk> finite A; A \<noteq> {} \<rbrakk> \<Longrightarrow> EX x. fold1Set f A x"
apply (induct A rule: finite_induct)
apply (auto dest: finite_imp_fold_graph [of _ f])
done
text{*First, some lemmas about @{const fold_graph}.*}
context ab_semigroup_mult
begin
lemma fun_left_comm: "fun_left_comm(op *)"
by unfold_locales (simp add: mult_ac)
lemma fold_graph_insert_swap:
assumes fold: "fold_graph times (b::'a) A y" and "b \<notin> A"
shows "fold_graph times z (insert b A) (z * y)"
proof -
interpret fun_left_comm "op *::'a \<Rightarrow> 'a \<Rightarrow> 'a" by (rule fun_left_comm)
from assms show ?thesis
proof (induct rule: fold_graph.induct)
case emptyI thus ?case by (force simp add: fold_insert_aux mult_commute)
next
case (insertI x A y)
have "fold_graph times z (insert x (insert b A)) (x * (z * y))"
using insertI by force --{*how does @{term id} get unfolded?*}
thus ?case by (simp add: insert_commute mult_ac)
qed
qed
lemma fold_graph_permute_diff:
assumes fold: "fold_graph times b A x"
shows "!!a. \<lbrakk>a \<in> A; b \<notin> A\<rbrakk> \<Longrightarrow> fold_graph times a (insert b (A-{a})) x"
using fold
proof (induct rule: fold_graph.induct)
case emptyI thus ?case by simp
next
case (insertI x A y)
have "a = x \<or> a \<in> A" using insertI by simp
thus ?case
proof
assume "a = x"
with insertI show ?thesis
by (simp add: id_def [symmetric], blast intro: fold_graph_insert_swap)
next
assume ainA: "a \<in> A"
hence "fold_graph times a (insert x (insert b (A - {a}))) (x * y)"
using insertI by force
moreover
have "insert x (insert b (A - {a})) = insert b (insert x A - {a})"
using ainA insertI by blast
ultimately show ?thesis by simp
qed
qed
lemma fold1_eq_fold:
assumes "finite A" "a \<notin> A" shows "fold1 times (insert a A) = fold times a A"
proof -
interpret fun_left_comm "op *::'a \<Rightarrow> 'a \<Rightarrow> 'a" by (rule fun_left_comm)
from assms show ?thesis
apply (simp add: fold1_def fold_def)
apply (rule the_equality)
apply (best intro: fold_graph_determ theI dest: finite_imp_fold_graph [of _ times])
apply (rule sym, clarify)
apply (case_tac "Aa=A")
apply (best intro: fold_graph_determ)
apply (subgoal_tac "fold_graph times a A x")
apply (best intro: fold_graph_determ)
apply (subgoal_tac "insert aa (Aa - {a}) = A")
prefer 2 apply (blast elim: equalityE)
apply (auto dest: fold_graph_permute_diff [where a=a])
done
qed
lemma nonempty_iff: "(A \<noteq> {}) = (\<exists>x B. A = insert x B & x \<notin> B)"
apply safe
apply simp
apply (drule_tac x=x in spec)
apply (drule_tac x="A-{x}" in spec, auto)
done
lemma fold1_insert:
assumes nonempty: "A \<noteq> {}" and A: "finite A" "x \<notin> A"
shows "fold1 times (insert x A) = x * fold1 times A"
proof -
interpret fun_left_comm "op *::'a \<Rightarrow> 'a \<Rightarrow> 'a" by (rule fun_left_comm)
from nonempty obtain a A' where "A = insert a A' & a ~: A'"
by (auto simp add: nonempty_iff)
with A show ?thesis
by (simp add: insert_commute [of x] fold1_eq_fold eq_commute)
qed
end
context ab_semigroup_idem_mult
begin
lemma fold1_insert_idem [simp]:
assumes nonempty: "A \<noteq> {}" and A: "finite A"
shows "fold1 times (insert x A) = x * fold1 times A"
proof -
interpret fun_left_comm_idem "op *::'a \<Rightarrow> 'a \<Rightarrow> 'a"
by (rule fun_left_comm_idem)
from nonempty obtain a A' where A': "A = insert a A' & a ~: A'"
by (auto simp add: nonempty_iff)
show ?thesis
proof cases
assume "a = x"
thus ?thesis
proof cases
assume "A' = {}"
with prems show ?thesis by simp
next
assume "A' \<noteq> {}"
with prems show ?thesis
by (simp add: fold1_insert mult_assoc [symmetric])
qed
next
assume "a \<noteq> x"
with prems show ?thesis
by (simp add: insert_commute fold1_eq_fold)
qed
qed
lemma hom_fold1_commute:
assumes hom: "!!x y. h (x * y) = h x * h y"
and N: "finite N" "N \<noteq> {}" shows "h (fold1 times N) = fold1 times (h ` N)"
using N proof (induct rule: finite_ne_induct)
case singleton thus ?case by simp
next
case (insert n N)
then have "h (fold1 times (insert n N)) = h (n * fold1 times N)" by simp
also have "\<dots> = h n * h (fold1 times N)" by(rule hom)
also have "h (fold1 times N) = fold1 times (h ` N)" by(rule insert)
also have "times (h n) \<dots> = fold1 times (insert (h n) (h ` N))"
using insert by(simp)
also have "insert (h n) (h ` N) = h ` insert n N" by simp
finally show ?case .
qed
lemma fold1_eq_fold_idem:
assumes "finite A"
shows "fold1 times (insert a A) = fold times a A"
proof (cases "a \<in> A")
case False
with assms show ?thesis by (simp add: fold1_eq_fold)
next
interpret fun_left_comm_idem times by (fact fun_left_comm_idem)
case True then obtain b B
where A: "A = insert a B" and "a \<notin> B" by (rule set_insert)
with assms have "finite B" by auto
then have "fold times a (insert a B) = fold times (a * a) B"
using `a \<notin> B` by (rule fold_insert2)
then show ?thesis
using `a \<notin> B` `finite B` by (simp add: fold1_eq_fold A)
qed
end
text{* Now the recursion rules for definitions: *}
lemma fold1_singleton_def: "g = fold1 f \<Longrightarrow> g {a} = a"
by simp
lemma (in ab_semigroup_mult) fold1_insert_def:
"\<lbrakk> g = fold1 times; finite A; x \<notin> A; A \<noteq> {} \<rbrakk> \<Longrightarrow> g (insert x A) = x * g A"
by (simp add:fold1_insert)
lemma (in ab_semigroup_idem_mult) fold1_insert_idem_def:
"\<lbrakk> g = fold1 times; finite A; A \<noteq> {} \<rbrakk> \<Longrightarrow> g (insert x A) = x * g A"
by simp
subsubsection{* Determinacy for @{term fold1Set} *}
(*Not actually used!!*)
(*
context ab_semigroup_mult
begin
lemma fold_graph_permute:
"[|fold_graph times id b (insert a A) x; a \<notin> A; b \<notin> A|]
==> fold_graph times id a (insert b A) x"
apply (cases "a=b")
apply (auto dest: fold_graph_permute_diff)
done
lemma fold1Set_determ:
"fold1Set times A x ==> fold1Set times A y ==> y = x"
proof (clarify elim!: fold1Set.cases)
fix A x B y a b
assume Ax: "fold_graph times id a A x"
assume By: "fold_graph times id b B y"
assume anotA: "a \<notin> A"
assume bnotB: "b \<notin> B"
assume eq: "insert a A = insert b B"
show "y=x"
proof cases
assume same: "a=b"
hence "A=B" using anotA bnotB eq by (blast elim!: equalityE)
thus ?thesis using Ax By same by (blast intro: fold_graph_determ)
next
assume diff: "a\<noteq>b"
let ?D = "B - {a}"
have B: "B = insert a ?D" and A: "A = insert b ?D"
and aB: "a \<in> B" and bA: "b \<in> A"
using eq anotA bnotB diff by (blast elim!:equalityE)+
with aB bnotB By
have "fold_graph times id a (insert b ?D) y"
by (auto intro: fold_graph_permute simp add: insert_absorb)
moreover
have "fold_graph times id a (insert b ?D) x"
by (simp add: A [symmetric] Ax)
ultimately show ?thesis by (blast intro: fold_graph_determ)
qed
qed
lemma fold1Set_equality: "fold1Set times A y ==> fold1 times A = y"
by (unfold fold1_def) (blast intro: fold1Set_determ)
end
*)
declare
empty_fold_graphE [rule del] fold_graph.intros [rule del]
empty_fold1SetE [rule del] insert_fold1SetE [rule del]
-- {* No more proofs involve these relations. *}
subsubsection {* Lemmas about @{text fold1} *}
context ab_semigroup_mult
begin
lemma fold1_Un:
assumes A: "finite A" "A \<noteq> {}"
shows "finite B \<Longrightarrow> B \<noteq> {} \<Longrightarrow> A Int B = {} \<Longrightarrow>
fold1 times (A Un B) = fold1 times A * fold1 times B"
using A by (induct rule: finite_ne_induct)
(simp_all add: fold1_insert mult_assoc)
lemma fold1_in:
assumes A: "finite (A)" "A \<noteq> {}" and elem: "\<And>x y. x * y \<in> {x,y}"
shows "fold1 times A \<in> A"
using A
proof (induct rule:finite_ne_induct)
case singleton thus ?case by simp
next
case insert thus ?case using elem by (force simp add:fold1_insert)
qed
end
lemma (in ab_semigroup_idem_mult) fold1_Un2:
assumes A: "finite A" "A \<noteq> {}"
shows "finite B \<Longrightarrow> B \<noteq> {} \<Longrightarrow>
fold1 times (A Un B) = fold1 times A * fold1 times B"
using A
proof(induct rule:finite_ne_induct)
case singleton thus ?case by simp
next
case insert thus ?case by (simp add: mult_assoc)
qed
subsection {* Expressing set operations via @{const fold} *}
lemma (in fun_left_comm) fun_left_comm_apply:
"fun_left_comm (\<lambda>x. f (g x))"
proof
qed (simp_all add: fun_left_comm)
lemma (in fun_left_comm_idem) fun_left_comm_idem_apply:
"fun_left_comm_idem (\<lambda>x. f (g x))"
by (rule fun_left_comm_idem.intro, rule fun_left_comm_apply, unfold_locales)
(simp_all add: fun_left_idem)
lemma fun_left_comm_idem_insert:
"fun_left_comm_idem insert"
proof
qed auto
lemma fun_left_comm_idem_remove:
"fun_left_comm_idem (\<lambda>x A. A - {x})"
proof
qed auto
lemma (in semilattice_inf) fun_left_comm_idem_inf:
"fun_left_comm_idem inf"
proof
qed (auto simp add: inf_left_commute)
lemma (in semilattice_sup) fun_left_comm_idem_sup:
"fun_left_comm_idem sup"
proof
qed (auto simp add: sup_left_commute)
lemma union_fold_insert:
assumes "finite A"
shows "A \<union> B = fold insert B A"
proof -
interpret fun_left_comm_idem insert by (fact fun_left_comm_idem_insert)
from `finite A` show ?thesis by (induct A arbitrary: B) simp_all
qed
lemma minus_fold_remove:
assumes "finite A"
shows "B - A = fold (\<lambda>x A. A - {x}) B A"
proof -
interpret fun_left_comm_idem "\<lambda>x A. A - {x}" by (fact fun_left_comm_idem_remove)
from `finite A` show ?thesis by (induct A arbitrary: B) auto
qed
context complete_lattice
begin
lemma inf_Inf_fold_inf:
assumes "finite A"
shows "inf B (Inf A) = fold inf B A"
proof -
interpret fun_left_comm_idem inf by (fact fun_left_comm_idem_inf)
from `finite A` show ?thesis by (induct A arbitrary: B)
(simp_all add: Inf_empty Inf_insert inf_commute fold_fun_comm)
qed
lemma sup_Sup_fold_sup:
assumes "finite A"
shows "sup B (Sup A) = fold sup B A"
proof -
interpret fun_left_comm_idem sup by (fact fun_left_comm_idem_sup)
from `finite A` show ?thesis by (induct A arbitrary: B)
(simp_all add: Sup_empty Sup_insert sup_commute fold_fun_comm)
qed
lemma Inf_fold_inf:
assumes "finite A"
shows "Inf A = fold inf top A"
using assms inf_Inf_fold_inf [of A top] by (simp add: inf_absorb2)
lemma Sup_fold_sup:
assumes "finite A"
shows "Sup A = fold sup bot A"
using assms sup_Sup_fold_sup [of A bot] by (simp add: sup_absorb2)
lemma inf_INFI_fold_inf:
assumes "finite A"
shows "inf B (INFI A f) = fold (\<lambda>A. inf (f A)) B A" (is "?inf = ?fold")
proof (rule sym)
interpret fun_left_comm_idem inf by (fact fun_left_comm_idem_inf)
interpret fun_left_comm_idem "\<lambda>A. inf (f A)" by (fact fun_left_comm_idem_apply)
from `finite A` show "?fold = ?inf"
by (induct A arbitrary: B)
(simp_all add: INFI_def Inf_empty Inf_insert inf_left_commute)
qed
lemma sup_SUPR_fold_sup:
assumes "finite A"
shows "sup B (SUPR A f) = fold (\<lambda>A. sup (f A)) B A" (is "?sup = ?fold")
proof (rule sym)
interpret fun_left_comm_idem sup by (fact fun_left_comm_idem_sup)
interpret fun_left_comm_idem "\<lambda>A. sup (f A)" by (fact fun_left_comm_idem_apply)
from `finite A` show "?fold = ?sup"
by (induct A arbitrary: B)
(simp_all add: SUPR_def Sup_empty Sup_insert sup_left_commute)
qed
lemma INFI_fold_inf:
assumes "finite A"
shows "INFI A f = fold (\<lambda>A. inf (f A)) top A"
using assms inf_INFI_fold_inf [of A top] by simp
lemma SUPR_fold_sup:
assumes "finite A"
shows "SUPR A f = fold (\<lambda>A. sup (f A)) bot A"
using assms sup_SUPR_fold_sup [of A bot] by simp
end
subsection {* Locales as mini-packages *}
locale folding =
fixes f :: "'a \<Rightarrow> 'b \<Rightarrow> 'b"
fixes F :: "'a set \<Rightarrow> 'b \<Rightarrow> 'b"
assumes commute_comp: "f x \<circ> f y = f y \<circ> f x"
assumes eq_fold: "F A s = Finite_Set.fold f s A"
begin
lemma fun_left_commute:
"f x (f y s) = f y (f x s)"
using commute_comp [of x y] by (simp add: expand_fun_eq)
lemma fun_left_comm:
"fun_left_comm f"
proof
qed (fact fun_left_commute)
lemma empty [simp]:
"F {} = id"
by (simp add: eq_fold expand_fun_eq)
lemma insert [simp]:
assumes "finite A" and "x \<notin> A"
shows "F (insert x A) = F A \<circ> f x"
proof -
interpret fun_left_comm f by (fact fun_left_comm)
from fold_insert2 assms
have "\<And>s. Finite_Set.fold f s (insert x A) = Finite_Set.fold f (f x s) A" .
then show ?thesis by (simp add: eq_fold expand_fun_eq)
qed
lemma remove:
assumes "finite A" and "x \<in> A"
shows "F A = F (A - {x}) \<circ> f x"
proof -
from `x \<in> A` obtain B where A: "A = insert x B" and "x \<notin> B"
by (auto dest: mk_disjoint_insert)
moreover from `finite A` this have "finite B" by simp
ultimately show ?thesis by simp
qed
lemma insert_remove:
assumes "finite A"
shows "F (insert x A) = F (A - {x}) \<circ> f x"
proof (cases "x \<in> A")
case True with assms show ?thesis by (simp add: remove insert_absorb)
next
case False with assms show ?thesis by simp
qed
lemma commute_comp':
assumes "finite A"
shows "f x \<circ> F A = F A \<circ> f x"
proof (rule ext)
fix s
from assms show "(f x \<circ> F A) s = (F A \<circ> f x) s"
by (induct A arbitrary: s) (simp_all add: fun_left_commute)
qed
lemma fun_left_commute':
assumes "finite A"
shows "f x (F A s) = F A (f x s)"
using commute_comp' assms by (simp add: expand_fun_eq)
lemma union:
assumes "finite A" and "finite B"
and "A \<inter> B = {}"
shows "F (A \<union> B) = F A \<circ> F B"
using `finite A` `A \<inter> B = {}` proof (induct A)
case empty show ?case by simp
next
case (insert x A)
then have "A \<inter> B = {}" by auto
with insert(3) have "F (A \<union> B) = F A \<circ> F B" .
moreover from insert have "x \<notin> B" by simp
moreover from `finite A` `finite B` have fin: "finite (A \<union> B)" by simp
moreover from `x \<notin> A` `x \<notin> B` have "x \<notin> A \<union> B" by simp
ultimately show ?case by (simp add: fun_left_commute')
qed
end
locale folding_idem = folding +
assumes idem_comp: "f x \<circ> f x = f x"
begin
declare insert [simp del]
lemma fun_idem:
"f x (f x s) = f x s"
using idem_comp [of x] by (simp add: expand_fun_eq)
lemma fun_left_comm_idem:
"fun_left_comm_idem f"
proof
qed (fact fun_left_commute fun_idem)+
lemma insert_idem [simp]:
assumes "finite A"
shows "F (insert x A) = F A \<circ> f x"
proof -
interpret fun_left_comm_idem f by (fact fun_left_comm_idem)
from fold_insert_idem2 assms
have "\<And>s. Finite_Set.fold f s (insert x A) = Finite_Set.fold f (f x s) A" .
then show ?thesis by (simp add: eq_fold expand_fun_eq)
qed
lemma union_idem:
assumes "finite A" and "finite B"
shows "F (A \<union> B) = F A \<circ> F B"
using `finite A` proof (induct A)
case empty show ?case by simp
next
case (insert x A)
from insert(3) have "F (A \<union> B) = F A \<circ> F B" .
moreover from `finite A` `finite B` have fin: "finite (A \<union> B)" by simp
ultimately show ?case by (simp add: fun_left_commute')
qed
end
end