Lemmas on dvd, power and finite summation added or strengthened.
(* Title: HOL/Finite_Set.thy
ID: $Id$
Author: Tobias Nipkow, Lawrence C Paulson and Markus Wenzel
with contributions by Jeremy Avigad
*)
header {* Finite sets *}
theory Finite_Set
imports Power Inductive Lattice_Locales
begin
subsection {* Definition and basic properties *}
consts Finites :: "'a set set"
syntax
finite :: "'a set => bool"
translations
"finite A" == "A : Finites"
inductive Finites
intros
emptyI [simp, intro!]: "{} : Finites"
insertI [simp, intro!]: "A : Finites ==> insert a A : Finites"
axclass finite \<subseteq> type
finite: "finite UNIV"
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 prems have "A \<noteq> UNIV" by blast
thus ?thesis by blast
qed
lemma finite_induct [case_names empty insert, induct set: Finites]:
"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 {}" .
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 insert(4) by simp
next
assume "F \<noteq> {}" thus ?thesis using insert by blast
qed
qed
lemma finite_subset_induct [consumes 2, case_names empty insert]:
"finite F ==> F \<subseteq> A ==>
P {} ==> (!!a F. finite F ==> a \<in> A ==> a \<notin> F ==> P F ==> P (insert a F)) ==>
P F"
proof -
assume "P {}" and insert:
"!!a F. finite F ==> a \<in> A ==> a \<notin> F ==> P F ==> P (insert a F)"
assume "finite F"
thus "F \<subseteq> A ==> P F"
proof induct
show "P {}" .
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" .
qed
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" .
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)
subsubsection{* Finiteness and set theoretic constructions *}
lemma finite_UnI: "finite F ==> finite G ==> finite (F Un G)"
-- {* The union of two finite sets is finite. *}
by (induct set: Finites) 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})" .
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" by (rule insert_Diff)
finally show ?thesis .
next
show "A \<subseteq> F ==> ?thesis" .
assume "x \<notin> A"
with A show "A \<subseteq> F" by (simp add: subset_insert_iff)
qed
qed
qed
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_Int [simp, intro]: "finite F | finite G ==> finite (F Int G)"
-- {* The converse obviously fails. *}
by (blast intro: finite_subset)
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_empty_induct:
"finite A ==>
P A ==> (!!a A. finite A ==> a:A ==> P A ==> P (A - {a})) ==> P {}"
proof -
assume "finite A"
and "P A" and "!!a A. finite A ==> a:A ==> P A ==> P (A - {a})"
have "P (A - A)"
proof -
fix c b :: "'a set"
presume 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})"
from c show "c \<subseteq> b ==> P (b - 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
next
show "A \<subseteq> A" ..
qed
thus "P {}" by simp
qed
lemma finite_Diff [simp]: "finite B ==> finite (B - Ba)"
by (rule Diff_subset [THEN finite_subset])
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: Finites) simp_all
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)
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: Finites, simp_all)
apply (subst vimage_insert)
apply (simp add: finite_Un finite_subset [OF inj_vimage_singleton])
done
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: Finites) 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_Plus: "[| finite A; finite B |] ==> finite (A <+> B)"
by (simp add: Plus_def)
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: finite_UnI finite_imageI Pow_insert)
qed
lemma finite_UnionD: "finite(\<Union>A) \<Longrightarrow> finite A"
by(blast intro: finite_subset[OF subset_Pow_Union])
lemma finite_converse [iff]: "finite (r^-1) = finite r"
apply (subgoal_tac "r^-1 = (%(x,y). (y,x))`r")
apply simp
apply (rule iffI)
apply (erule finite_imageD [unfolded inj_on_def])
apply (simp split add: split_split)
apply (erule finite_imageI)
apply (simp add: converse_def image_def, auto)
apply (rule bexI)
prefer 2 apply assumption
apply simp
done
text {* \paragraph{Finiteness of transitive closure} (Thanks to Sidi
Ehmety) *}
lemma finite_Field: "finite r ==> finite (Field r)"
-- {* A finite relation has a finite field (@{text "= domain \<union> range"}. *}
apply (induct set: Finites)
apply (auto simp add: Field_def Domain_insert Range_insert)
done
lemma trancl_subset_Field2: "r^+ <= Field r \<times> Field r"
apply clarify
apply (erule trancl_induct)
apply (auto simp add: Field_def)
done
lemma finite_trancl: "finite (r^+) = finite r"
apply auto
prefer 2
apply (rule trancl_subset_Field2 [THEN finite_subset])
apply (rule finite_SigmaI)
prefer 3
apply (blast intro: r_into_trancl' finite_subset)
apply (auto simp add: finite_Field)
done
subsection {* A fold functional for finite sets *}
text {* The intended behaviour is
@{text "fold f g z {x\<^isub>1, ..., x\<^isub>n} = f (g x\<^isub>1) (\<dots> (f (g x\<^isub>n) z)\<dots>)"}
if @{text f} is associative-commutative. For an application of @{text fold}
se the definitions of sums and products over finite sets.
*}
consts
foldSet :: "('a => 'a => 'a) => ('b => 'a) => 'a => ('b set \<times> 'a) set"
inductive "foldSet f g z"
intros
emptyI [intro]: "({}, z) : foldSet f g z"
insertI [intro]:
"\<lbrakk> x \<notin> A; (A, y) : foldSet f g z \<rbrakk>
\<Longrightarrow> (insert x A, f (g x) y) : foldSet f g z"
inductive_cases empty_foldSetE [elim!]: "({}, x) : foldSet f g z"
constdefs
fold :: "('a => 'a => 'a) => ('b => 'a) => 'a => 'b set => 'a"
"fold f g z A == THE x. (A, x) : foldSet f g z"
text{*A tempting alternative for the definiens is
@{term "if finite A then THE x. (A, x) : foldSet f g e else e"}.
It allows the removal of finiteness assumptions from the theorems
@{text fold_commute}, @{text fold_reindex} and @{text fold_distrib}.
The proofs become ugly, with @{text rule_format}. It is not worth the effort.*}
lemma Diff1_foldSet:
"(A - {x}, y) : foldSet f g z ==> x: A ==> (A, f (g x) y) : foldSet f g z"
by (erule insert_Diff [THEN subst], rule foldSet.intros, auto)
lemma foldSet_imp_finite: "(A, x) : foldSet f g z ==> finite A"
by (induct set: foldSet) auto
lemma finite_imp_foldSet: "finite A ==> EX x. (A, x) : foldSet f g z"
by (induct set: Finites) auto
subsubsection {* Commutative monoids *}
locale ACf =
fixes f :: "'a => 'a => 'a" (infixl "\<cdot>" 70)
assumes commute: "x \<cdot> y = y \<cdot> x"
and assoc: "(x \<cdot> y) \<cdot> z = x \<cdot> (y \<cdot> z)"
locale ACe = ACf +
fixes e :: 'a
assumes ident [simp]: "x \<cdot> e = x"
locale ACIf = ACf +
assumes idem: "x \<cdot> x = x"
lemma (in ACf) left_commute: "x \<cdot> (y \<cdot> z) = y \<cdot> (x \<cdot> z)"
proof -
have "x \<cdot> (y \<cdot> z) = (y \<cdot> z) \<cdot> x" by (simp only: commute)
also have "... = y \<cdot> (z \<cdot> x)" by (simp only: assoc)
also have "z \<cdot> x = x \<cdot> z" by (simp only: commute)
finally show ?thesis .
qed
lemmas (in ACf) AC = assoc commute left_commute
lemma (in ACe) left_ident [simp]: "e \<cdot> x = x"
proof -
have "x \<cdot> e = x" by (rule ident)
thus ?thesis by (subst commute)
qed
lemma (in ACIf) idem2: "x \<cdot> (x \<cdot> y) = x \<cdot> y"
proof -
have "x \<cdot> (x \<cdot> y) = (x \<cdot> x) \<cdot> y" by(simp add:assoc)
also have "\<dots> = x \<cdot> y" by(simp add:idem)
finally show ?thesis .
qed
lemmas (in ACIf) ACI = AC idem idem2
text{* Interpretation of locales: *}
interpretation AC_add: ACe ["op +" "0::'a::comm_monoid_add"]
by(auto intro: ACf.intro ACe_axioms.intro add_assoc add_commute)
interpretation AC_mult: ACe ["op *" "1::'a::comm_monoid_mult"]
apply -
apply (fast intro: ACf.intro mult_assoc mult_commute)
apply (fastsimp intro: ACe_axioms.intro mult_assoc mult_commute)
done
subsubsection{*From @{term foldSet} 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" .
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 = "swap k m h"
have inj_hm: "inj_on ?hm {i. i < n}" using klessn mlessn
by (simp add: inj_on_swap_iff 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 (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
lemma (in ACf) foldSet_determ_aux:
"!!A x x' h. \<lbrakk> A = h`{i::nat. i<n}; inj_on h {i. i<n};
(A,x) : foldSet f g z; (A,x') : foldSet f g z \<rbrakk>
\<Longrightarrow> x' = x"
proof (induct n rule: less_induct)
case (less n)
have IH: "!!m h A x x'.
\<lbrakk>m<n; A = h ` {i. i<m}; inj_on h {i. i<m};
(A,x) \<in> foldSet f g z; (A, x') \<in> foldSet f g z\<rbrakk> \<Longrightarrow> x' = x" .
have Afoldx: "(A,x) \<in> foldSet f g z" and Afoldx': "(A,x') \<in> foldSet f g z"
and A: "A = h`{i. i<n}" and injh: "inj_on h {i. i<n}" .
show ?case
proof (rule foldSet.cases [OF Afoldx])
assume "(A, x) = ({}, z)"
with Afoldx' show "x' = x" by blast
next
fix B b u
assume "(A,x) = (insert b B, g b \<cdot> u)" and notinB: "b \<notin> B"
and Bu: "(B,u) \<in> foldSet f g z"
hence AbB: "A = insert b B" and x: "x = g b \<cdot> u" by auto
show "x'=x"
proof (rule foldSet.cases [OF Afoldx'])
assume "(A, x') = ({}, z)"
with AbB show "x' = x" by blast
next
fix C c v
assume "(A,x') = (insert c C, g c \<cdot> v)" and notinC: "c \<notin> C"
and Cv: "(C,v) \<in> foldSet f g z"
hence AcC: "A = insert c C" and x': "x' = g c \<cdot> v" by auto
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 foldSet_imp_finite[OF Afoldx])
with AbB have "finite ?D" by simp
then obtain d where Dfoldd: "(?D,d) \<in> foldSet f g z"
using finite_imp_foldSet by rules
moreover have cinB: "c \<in> B" using B by auto
ultimately have "(B,g c \<cdot> d) \<in> foldSet f g z"
by(rule Diff1_foldSet)
hence "g c \<cdot> d = u" by (rule IH [OF lessB Beq inj_onB Bu])
moreover have "g b \<cdot> d = v"
proof (rule IH[OF lessC Ceq inj_onC Cv])
show "(C, g b \<cdot> d) \<in> foldSet f g z" using C notinB Dfoldd
by fastsimp
qed
ultimately show ?thesis using x x' by (auto simp: AC)
qed
qed
qed
qed
lemma (in ACf) foldSet_determ:
"(A,x) : foldSet f g z ==> (A,y) : foldSet f g z ==> y = x"
apply (frule foldSet_imp_finite [THEN finite_imp_nat_seg_image_inj_on])
apply (blast intro: foldSet_determ_aux [rule_format])
done
lemma (in ACf) fold_equality: "(A, y) : foldSet f g z ==> fold f g z A = y"
by (unfold fold_def) (blast intro: foldSet_determ)
text{* The base case for @{text fold}: *}
lemma fold_empty [simp]: "fold f g z {} = z"
by (unfold fold_def) blast
lemma (in ACf) fold_insert_aux: "x \<notin> A ==>
((insert x A, v) : foldSet f g z) =
(EX y. (A, y) : foldSet f g z & v = f (g x) y)"
apply auto
apply (rule_tac A1 = A and f1 = f in finite_imp_foldSet [THEN exE])
apply (fastsimp dest: foldSet_imp_finite)
apply (blast intro: foldSet_determ)
done
text{* The recursion equation for @{text fold}: *}
lemma (in ACf) fold_insert[simp]:
"finite A ==> x \<notin> A ==> fold f g z (insert x A) = f (g x) (fold f g z A)"
apply (unfold fold_def)
apply (simp add: fold_insert_aux)
apply (rule the_equality)
apply (auto intro: finite_imp_foldSet
cong add: conj_cong simp add: fold_def [symmetric] fold_equality)
done
lemma (in ACf) fold_rec:
assumes fin: "finite A" and a: "a:A"
shows "fold f g z A = f (g a) (fold f g z (A - {a}))"
proof-
have A: "A = insert a (A - {a})" using a by blast
hence "fold f g z A = fold f g z (insert a (A - {a}))" by simp
also have "\<dots> = f (g a) (fold f g z (A - {a}))"
by(rule fold_insert) (simp add:fin)+
finally show ?thesis .
qed
text{* A simplified version for idempotent functions: *}
lemma (in ACIf) fold_insert_idem:
assumes finA: "finite A"
shows "fold f g z (insert a A) = g a \<cdot> fold f g z A"
proof cases
assume "a \<in> A"
then obtain B where A: "A = insert a B" and disj: "a \<notin> B"
by(blast dest: mk_disjoint_insert)
show ?thesis
proof -
from finA A have finB: "finite B" by(blast intro: finite_subset)
have "fold f g z (insert a A) = fold f g z (insert a B)" using A by simp
also have "\<dots> = (g a) \<cdot> (fold f g z B)"
using finB disj by simp
also have "\<dots> = g a \<cdot> fold f g z A"
using A finB disj by(simp add:idem assoc[symmetric])
finally show ?thesis .
qed
next
assume "a \<notin> A"
with finA show ?thesis by simp
qed
lemma (in ACIf) foldI_conv_id:
"finite A \<Longrightarrow> fold f g z A = fold f id z (g ` A)"
by(erule finite_induct)(simp_all add: fold_insert_idem del: fold_insert)
subsubsection{*Lemmas about @{text fold}*}
lemma (in ACf) fold_commute:
"finite A ==> (!!z. f x (fold f g z A) = fold f g (f x z) A)"
apply (induct set: Finites, simp)
apply (simp add: left_commute [of x])
done
lemma (in ACf) fold_nest_Un_Int:
"finite A ==> finite B
==> fold f g (fold f g z B) A = fold f g (fold f g z (A Int B)) (A Un B)"
apply (induct set: Finites, simp)
apply (simp add: fold_commute Int_insert_left insert_absorb)
done
lemma (in ACf) fold_nest_Un_disjoint:
"finite A ==> finite B ==> A Int B = {}
==> fold f g z (A Un B) = fold f g (fold f g z B) A"
by (simp add: fold_nest_Un_Int)
lemma (in ACf) fold_reindex:
assumes fin: "finite A"
shows "inj_on h A \<Longrightarrow> fold f g z (h ` A) = fold f (g \<circ> h) z A"
using fin apply induct
apply simp
apply simp
done
lemma (in ACe) fold_Un_Int:
"finite A ==> finite B ==>
fold f g e A \<cdot> fold f g e B =
fold f g e (A Un B) \<cdot> fold f g e (A Int B)"
apply (induct set: Finites, simp)
apply (simp add: AC insert_absorb Int_insert_left)
done
corollary (in ACe) fold_Un_disjoint:
"finite A ==> finite B ==> A Int B = {} ==>
fold f g e (A Un B) = fold f g e A \<cdot> fold f g e B"
by (simp add: fold_Un_Int)
lemma (in ACe) fold_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 f g e (UNION I A) =
fold f (%i. fold f g e (A i)) e I"
apply (induct set: Finites, 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
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 (in ACf) fold_fusion:
includes ACf g
shows
"finite A ==>
(!!x y. h (g x y) = f x (h y)) ==>
h (fold g j w A) = fold f j (h w) A"
by (induct set: Finites, simp_all)
lemma (in ACf) fold_cong:
"finite A \<Longrightarrow> (!!x. x:A ==> g x = h x) ==> fold f g z A = fold f h z A"
apply (subgoal_tac "ALL C. C <= A --> (ALL x:C. g x = h x) --> fold f g z C = fold f 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
lemma (in ACe) fold_Sigma: "finite A ==> ALL x:A. finite (B x) ==>
fold f (%x. fold f (g x) e (B x)) e A =
fold f (split g) e (SIGMA x:A. B x)"
apply (subst Sigma_def)
apply (subst fold_UN_disjoint, assumption, simp)
apply blast
apply (erule fold_cong)
apply (subst fold_UN_disjoint, simp, simp)
apply blast
apply simp
done
lemma (in ACe) fold_distrib: "finite A \<Longrightarrow>
fold f (%x. f (g x) (h x)) e A = f (fold f g e A) (fold f h e A)"
apply (erule finite_induct, simp)
apply (simp add:AC)
done
subsection {* Generalized summation over a set *}
constdefs
setsum :: "('a => 'b) => 'a set => 'b::comm_monoid_add"
"setsum f A == if finite A then fold (op +) f 0 A else 0"
text{* Now: lot's of fancy syntax. First, @{term "setsum (%x. e) A"} is
written @{text"\<Sum>x\<in>A. e"}. *}
syntax
"_setsum" :: "idt => 'a set => 'b => 'b::comm_monoid_add" ("(3SUM _:_. _)" [0, 51, 10] 10)
syntax (xsymbols)
"_setsum" :: "idt => 'a set => 'b => 'b::comm_monoid_add" ("(3\<Sum>_\<in>_. _)" [0, 51, 10] 10)
syntax (HTML output)
"_setsum" :: "idt => 'a set => 'b => 'b::comm_monoid_add" ("(3\<Sum>_\<in>_. _)" [0, 51, 10] 10)
translations -- {* Beware of argument permutation! *}
"SUM i:A. b" == "setsum (%i. b) A"
"\<Sum>i\<in>A. b" == "setsum (%i. b) A"
text{* Instead of @{term"\<Sum>x\<in>{x. P}. e"} we introduce the shorter
@{text"\<Sum>x|P. e"}. *}
syntax
"_qsetsum" :: "idt \<Rightarrow> bool \<Rightarrow> 'a \<Rightarrow> 'a" ("(3SUM _ |/ _./ _)" [0,0,10] 10)
syntax (xsymbols)
"_qsetsum" :: "idt \<Rightarrow> bool \<Rightarrow> 'a \<Rightarrow> 'a" ("(3\<Sum>_ | (_)./ _)" [0,0,10] 10)
syntax (HTML output)
"_qsetsum" :: "idt \<Rightarrow> bool \<Rightarrow> 'a \<Rightarrow> 'a" ("(3\<Sum>_ | (_)./ _)" [0,0,10] 10)
translations
"SUM x|P. t" => "setsum (%x. t) {x. P}"
"\<Sum>x|P. t" => "setsum (%x. t) {x. P}"
text{* Finally we abbreviate @{term"\<Sum>x\<in>A. x"} by @{text"\<Sum>A"}. *}
syntax
"_Setsum" :: "'a set => 'a::comm_monoid_mult" ("\<Sum>_" [1000] 999)
parse_translation {*
let
fun Setsum_tr [A] = Syntax.const "setsum" $ Abs ("", dummyT, Bound 0) $ A
in [("_Setsum", Setsum_tr)] end;
*}
print_translation {*
let
fun setsum_tr' [Abs(_,_,Bound 0), A] = Syntax.const "_Setsum" $ A
| setsum_tr' [Abs(x,Tx,t), Const ("Collect",_) $ Abs(y,Ty,P)] =
if x<>y then raise Match
else let val x' = Syntax.mark_bound x
val t' = subst_bound(x',t)
val P' = subst_bound(x',P)
in Syntax.const "_qsetsum" $ Syntax.mark_bound x $ P' $ t' end
in
[("setsum", setsum_tr')]
end
*}
lemma setsum_empty [simp]: "setsum f {} = 0"
by (simp add: setsum_def)
lemma setsum_insert [simp]:
"finite F ==> a \<notin> F ==> setsum f (insert a F) = f a + setsum f F"
by (simp add: setsum_def)
lemma setsum_infinite [simp]: "~ finite A ==> setsum f A = 0"
by (simp add: setsum_def)
lemma setsum_reindex:
"inj_on f B ==> setsum h (f ` B) = setsum (h \<circ> f) B"
by(auto simp add: setsum_def AC_add.fold_reindex dest!:finite_imageD)
lemma setsum_reindex_id:
"inj_on f B ==> setsum f B = setsum id (f ` B)"
by (auto simp add: setsum_reindex)
lemma setsum_cong:
"A = B ==> (!!x. x:B ==> f x = g x) ==> setsum f A = setsum g B"
by(fastsimp simp: setsum_def intro: AC_add.fold_cong)
lemma strong_setsum_cong[cong]:
"A = B ==> (!!x. x:B =simp=> f x = g x)
==> setsum (%x. f x) A = setsum (%x. g x) B"
by(fastsimp simp: simp_implies_def setsum_def intro: AC_add.fold_cong)
lemma setsum_cong2: "\<lbrakk>\<And>x. x \<in> A \<Longrightarrow> f x = g x\<rbrakk> \<Longrightarrow> setsum f A = setsum g A";
by (rule setsum_cong[OF refl], auto);
lemma setsum_reindex_cong:
"[|inj_on f A; B = f ` A; !!a. a:A \<Longrightarrow> g a = h (f a)|]
==> setsum h B = setsum g A"
by (simp add: setsum_reindex cong: setsum_cong)
lemma setsum_0[simp]: "setsum (%i. 0) A = 0"
apply (clarsimp simp: setsum_def)
apply (erule finite_induct, auto)
done
lemma setsum_0': "ALL a:A. f a = 0 ==> setsum f A = 0"
by(simp add:setsum_cong)
lemma setsum_Un_Int: "finite A ==> finite B ==>
setsum g (A Un B) + setsum g (A Int B) = setsum g A + setsum g B"
-- {* The reversed orientation looks more natural, but LOOPS as a simprule! *}
by(simp add: setsum_def AC_add.fold_Un_Int [symmetric])
lemma setsum_Un_disjoint: "finite A ==> finite B
==> A Int B = {} ==> setsum g (A Un B) = setsum g A + setsum g B"
by (subst setsum_Un_Int [symmetric], auto)
(*But we can't get rid of finite I. If infinite, although the rhs is 0,
the lhs need not be, since UNION I A could still be finite.*)
lemma setsum_UN_disjoint:
"finite I ==> (ALL i:I. finite (A i)) ==>
(ALL i:I. ALL j:I. i \<noteq> j --> A i Int A j = {}) ==>
setsum f (UNION I A) = (\<Sum>i\<in>I. setsum f (A i))"
by(simp add: setsum_def AC_add.fold_UN_disjoint cong: setsum_cong)
text{*No need to assume that @{term C} is finite. If infinite, the rhs is
directly 0, and @{term "Union C"} is also infinite, hence the lhs is also 0.*}
lemma setsum_Union_disjoint:
"[| (ALL A:C. finite A);
(ALL A:C. ALL B:C. A \<noteq> B --> A Int B = {}) |]
==> setsum f (Union C) = setsum (setsum f) C"
apply (cases "finite C")
prefer 2 apply (force dest: finite_UnionD simp add: setsum_def)
apply (frule setsum_UN_disjoint [of C id f])
apply (unfold Union_def id_def, assumption+)
done
(*But we can't get rid of finite A. If infinite, although the lhs is 0,
the rhs need not be, since SIGMA A B could still be finite.*)
lemma setsum_Sigma: "finite A ==> ALL x:A. finite (B x) ==>
(\<Sum>x\<in>A. (\<Sum>y\<in>B x. f x y)) =
(\<Sum>z\<in>(SIGMA x:A. B x). f (fst z) (snd z))"
by(simp add:setsum_def AC_add.fold_Sigma split_def cong:setsum_cong)
text{*Here we can eliminate the finiteness assumptions, by cases.*}
lemma setsum_cartesian_product:
"(\<Sum>x\<in>A. (\<Sum>y\<in>B. f x y)) = (\<Sum>z\<in>A <*> B. f (fst z) (snd z))"
apply (cases "finite A")
apply (cases "finite B")
apply (simp add: setsum_Sigma)
apply (cases "A={}", simp)
apply (simp)
apply (auto simp add: setsum_def
dest: finite_cartesian_productD1 finite_cartesian_productD2)
done
lemma setsum_addf: "setsum (%x. f x + g x) A = (setsum f A + setsum g A)"
by(simp add:setsum_def AC_add.fold_distrib)
subsubsection {* Properties in more restricted classes of structures *}
lemma setsum_SucD: "setsum f A = Suc n ==> EX a:A. 0 < f a"
apply (case_tac "finite A")
prefer 2 apply (simp add: setsum_def)
apply (erule rev_mp)
apply (erule finite_induct, auto)
done
lemma setsum_eq_0_iff [simp]:
"finite F ==> (setsum f F = 0) = (ALL a:F. f a = (0::nat))"
by (induct set: Finites) auto
lemma setsum_Un_nat: "finite A ==> finite B ==>
(setsum f (A Un B) :: nat) = setsum f A + setsum f B - setsum f (A Int B)"
-- {* For the natural numbers, we have subtraction. *}
by (subst setsum_Un_Int [symmetric], auto simp add: ring_eq_simps)
lemma setsum_Un: "finite A ==> finite B ==>
(setsum f (A Un B) :: 'a :: ab_group_add) =
setsum f A + setsum f B - setsum f (A Int B)"
by (subst setsum_Un_Int [symmetric], auto simp add: ring_eq_simps)
lemma setsum_diff1_nat: "(setsum f (A - {a}) :: nat) =
(if a:A then setsum f A - f a else setsum f A)"
apply (case_tac "finite A")
prefer 2 apply (simp add: setsum_def)
apply (erule finite_induct)
apply (auto simp add: insert_Diff_if)
apply (drule_tac a = a in mk_disjoint_insert, auto)
done
lemma setsum_diff1: "finite A \<Longrightarrow>
(setsum f (A - {a}) :: ('a::ab_group_add)) =
(if a:A then setsum f A - f a else setsum f A)"
by (erule finite_induct) (auto simp add: insert_Diff_if)
lemma setsum_diff1'[rule_format]: "finite A \<Longrightarrow> a \<in> A \<longrightarrow> (\<Sum> x \<in> A. f x) = f a + (\<Sum> x \<in> (A - {a}). f x)"
apply (erule finite_induct[where F=A and P="% A. (a \<in> A \<longrightarrow> (\<Sum> x \<in> A. f x) = f a + (\<Sum> x \<in> (A - {a}). f x))"])
apply (auto simp add: insert_Diff_if add_ac)
done
(* By Jeremy Siek: *)
lemma setsum_diff_nat:
assumes finB: "finite B"
shows "B \<subseteq> A \<Longrightarrow> (setsum f (A - B) :: nat) = (setsum f A) - (setsum f B)"
using finB
proof (induct)
show "setsum f (A - {}) = (setsum f A) - (setsum f {})" by simp
next
fix F x assume finF: "finite F" and xnotinF: "x \<notin> F"
and xFinA: "insert x F \<subseteq> A"
and IH: "F \<subseteq> A \<Longrightarrow> setsum f (A - F) = setsum f A - setsum f F"
from xnotinF xFinA have xinAF: "x \<in> (A - F)" by simp
from xinAF have A: "setsum f ((A - F) - {x}) = setsum f (A - F) - f x"
by (simp add: setsum_diff1_nat)
from xFinA have "F \<subseteq> A" by simp
with IH have "setsum f (A - F) = setsum f A - setsum f F" by simp
with A have B: "setsum f ((A - F) - {x}) = setsum f A - setsum f F - f x"
by simp
from xnotinF have "A - insert x F = (A - F) - {x}" by auto
with B have C: "setsum f (A - insert x F) = setsum f A - setsum f F - f x"
by simp
from finF xnotinF have "setsum f (insert x F) = setsum f F + f x" by simp
with C have "setsum f (A - insert x F) = setsum f A - setsum f (insert x F)"
by simp
thus "setsum f (A - insert x F) = setsum f A - setsum f (insert x F)" by simp
qed
lemma setsum_diff:
assumes le: "finite A" "B \<subseteq> A"
shows "setsum f (A - B) = setsum f A - ((setsum f B)::('a::ab_group_add))"
proof -
from le have finiteB: "finite B" using finite_subset by auto
show ?thesis using finiteB le
proof (induct)
case empty
thus ?case by auto
next
case (insert x F)
thus ?case using le finiteB
by (simp add: Diff_insert[where a=x and B=F] setsum_diff1 insert_absorb)
qed
qed
lemma setsum_mono:
assumes le: "\<And>i. i\<in>K \<Longrightarrow> f (i::'a) \<le> ((g i)::('b::{comm_monoid_add, pordered_ab_semigroup_add}))"
shows "(\<Sum>i\<in>K. f i) \<le> (\<Sum>i\<in>K. g i)"
proof (cases "finite K")
case True
thus ?thesis using le
proof (induct)
case empty
thus ?case by simp
next
case insert
thus ?case using add_mono
by force
qed
next
case False
thus ?thesis
by (simp add: setsum_def)
qed
lemma setsum_strict_mono:
fixes f :: "'a \<Rightarrow> 'b::{pordered_cancel_ab_semigroup_add,comm_monoid_add}"
assumes fin_ne: "finite A" "A \<noteq> {}"
shows "(!!x. x:A \<Longrightarrow> f x < g x) \<Longrightarrow> setsum f A < setsum g A"
using fin_ne
proof (induct rule: finite_ne_induct)
case singleton thus ?case by simp
next
case insert thus ?case by (auto simp: add_strict_mono)
qed
lemma setsum_negf:
"setsum (%x. - (f x)::'a::ab_group_add) A = - setsum f A"
proof (cases "finite A")
case True thus ?thesis by (induct set: Finites, auto)
next
case False thus ?thesis by (simp add: setsum_def)
qed
lemma setsum_subtractf:
"setsum (%x. ((f x)::'a::ab_group_add) - g x) A =
setsum f A - setsum g A"
proof (cases "finite A")
case True thus ?thesis by (simp add: diff_minus setsum_addf setsum_negf)
next
case False thus ?thesis by (simp add: setsum_def)
qed
lemma setsum_nonneg:
assumes nn: "\<forall>x\<in>A. (0::'a::{pordered_ab_semigroup_add,comm_monoid_add}) \<le> f x"
shows "0 \<le> setsum f A"
proof (cases "finite A")
case True thus ?thesis using nn
apply (induct set: Finites, auto)
apply (subgoal_tac "0 + 0 \<le> f x + setsum f F", simp)
apply (blast intro: add_mono)
done
next
case False thus ?thesis by (simp add: setsum_def)
qed
lemma setsum_nonpos:
assumes np: "\<forall>x\<in>A. f x \<le> (0::'a::{pordered_ab_semigroup_add,comm_monoid_add})"
shows "setsum f A \<le> 0"
proof (cases "finite A")
case True thus ?thesis using np
apply (induct set: Finites, auto)
apply (subgoal_tac "f x + setsum f F \<le> 0 + 0", simp)
apply (blast intro: add_mono)
done
next
case False thus ?thesis by (simp add: setsum_def)
qed
lemma setsum_mono2:
fixes f :: "'a \<Rightarrow> 'b :: {pordered_ab_semigroup_add_imp_le,comm_monoid_add}"
assumes fin: "finite B" and sub: "A \<subseteq> B" and nn: "\<And>b. b \<in> B-A \<Longrightarrow> 0 \<le> f b"
shows "setsum f A \<le> setsum f B"
proof -
have "setsum f A \<le> setsum f A + setsum f (B-A)"
by(simp add: add_increasing2[OF setsum_nonneg] nn Ball_def)
also have "\<dots> = setsum f (A \<union> (B-A))" using fin finite_subset[OF sub fin]
by (simp add:setsum_Un_disjoint del:Un_Diff_cancel)
also have "A \<union> (B-A) = B" using sub by blast
finally show ?thesis .
qed
lemma setsum_mono3: "finite B ==> A <= B ==>
ALL x: B - A.
0 <= ((f x)::'a::{comm_monoid_add,pordered_ab_semigroup_add}) ==>
setsum f A <= setsum f B"
apply (subgoal_tac "setsum f B = setsum f A + setsum f (B - A)")
apply (erule ssubst)
apply (subgoal_tac "setsum f A + 0 <= setsum f A + setsum f (B - A)")
apply simp
apply (rule add_left_mono)
apply (erule setsum_nonneg)
apply (subst setsum_Un_disjoint [THEN sym])
apply (erule finite_subset, assumption)
apply (rule finite_subset)
prefer 2
apply assumption
apply auto
apply (rule setsum_cong)
apply auto
done
(* FIXME: this is distributitivty, name as such! *)
(* suggested name: setsum_right_distrib (CB) *)
lemma setsum_mult:
fixes f :: "'a => ('b::semiring_0_cancel)"
shows "r * setsum f A = setsum (%n. r * f n) A"
proof (cases "finite A")
case True
thus ?thesis
proof (induct)
case empty thus ?case by simp
next
case (insert x A) thus ?case by (simp add: right_distrib)
qed
next
case False thus ?thesis by (simp add: setsum_def)
qed
lemma setsum_left_distrib:
"setsum f A * (r::'a::semiring_0_cancel) = (\<Sum>n\<in>A. f n * r)"
proof (cases "finite A")
case True
then show ?thesis
proof induct
case empty thus ?case by simp
next
case (insert x A) thus ?case by (simp add: left_distrib)
qed
next
case False thus ?thesis by (simp add: setsum_def)
qed
lemma setsum_divide_distrib:
"setsum f A / (r::'a::field) = (\<Sum>n\<in>A. f n / r)"
proof (cases "finite A")
case True
then show ?thesis
proof induct
case empty thus ?case by simp
next
case (insert x A) thus ?case by (simp add: add_divide_distrib)
qed
next
case False thus ?thesis by (simp add: setsum_def)
qed
lemma setsum_abs[iff]:
fixes f :: "'a => ('b::lordered_ab_group_abs)"
shows "abs (setsum f A) \<le> setsum (%i. abs(f i)) A"
proof (cases "finite A")
case True
thus ?thesis
proof (induct)
case empty thus ?case by simp
next
case (insert x A)
thus ?case by (auto intro: abs_triangle_ineq order_trans)
qed
next
case False thus ?thesis by (simp add: setsum_def)
qed
lemma setsum_abs_ge_zero[iff]:
fixes f :: "'a => ('b::lordered_ab_group_abs)"
shows "0 \<le> setsum (%i. abs(f i)) A"
proof (cases "finite A")
case True
thus ?thesis
proof (induct)
case empty thus ?case by simp
next
case (insert x A) thus ?case by (auto intro: order_trans)
qed
next
case False thus ?thesis by (simp add: setsum_def)
qed
lemma abs_setsum_abs[simp]:
fixes f :: "'a => ('b::lordered_ab_group_abs)"
shows "abs (\<Sum>a\<in>A. abs(f a)) = (\<Sum>a\<in>A. abs(f a))"
proof (cases "finite A")
case True
thus ?thesis
proof (induct)
case empty thus ?case by simp
next
case (insert a A)
hence "\<bar>\<Sum>a\<in>insert a A. \<bar>f a\<bar>\<bar> = \<bar>\<bar>f a\<bar> + (\<Sum>a\<in>A. \<bar>f a\<bar>)\<bar>" by simp
also have "\<dots> = \<bar>\<bar>f a\<bar> + \<bar>\<Sum>a\<in>A. \<bar>f a\<bar>\<bar>\<bar>" using insert by simp
also have "\<dots> = \<bar>f a\<bar> + \<bar>\<Sum>a\<in>A. \<bar>f a\<bar>\<bar>"
by (simp del: abs_of_nonneg)
also have "\<dots> = (\<Sum>a\<in>insert a A. \<bar>f a\<bar>)" using insert by simp
finally show ?case .
qed
next
case False thus ?thesis by (simp add: setsum_def)
qed
text {* Commuting outer and inner summation *}
lemma swap_inj_on:
"inj_on (%(i, j). (j, i)) (A \<times> B)"
by (unfold inj_on_def) fast
lemma swap_product:
"(%(i, j). (j, i)) ` (A \<times> B) = B \<times> A"
by (simp add: split_def image_def) blast
lemma setsum_commute:
"(\<Sum>i\<in>A. \<Sum>j\<in>B. f i j) = (\<Sum>j\<in>B. \<Sum>i\<in>A. f i j)"
proof (simp add: setsum_cartesian_product)
have "(\<Sum>z\<in>A \<times> B. f (fst z) (snd z)) =
(\<Sum>z\<in>(%(i, j). (j, i)) ` (A \<times> B). f (snd z) (fst z))"
(is "?s = _")
apply (simp add: setsum_reindex [where f = "%(i, j). (j, i)"] swap_inj_on)
apply (simp add: split_def)
done
also have "... = (\<Sum>z\<in>B \<times> A. f (snd z) (fst z))"
(is "_ = ?t")
apply (simp add: swap_product)
done
finally show "?s = ?t" .
qed
subsection {* Generalized product over a set *}
constdefs
setprod :: "('a => 'b) => 'a set => 'b::comm_monoid_mult"
"setprod f A == if finite A then fold (op *) f 1 A else 1"
syntax
"_setprod" :: "idt => 'a set => 'b => 'b::comm_monoid_mult" ("(3PROD _:_. _)" [0, 51, 10] 10)
syntax (xsymbols)
"_setprod" :: "idt => 'a set => 'b => 'b::comm_monoid_mult" ("(3\<Prod>_\<in>_. _)" [0, 51, 10] 10)
syntax (HTML output)
"_setprod" :: "idt => 'a set => 'b => 'b::comm_monoid_mult" ("(3\<Prod>_\<in>_. _)" [0, 51, 10] 10)
translations -- {* Beware of argument permutation! *}
"PROD i:A. b" == "setprod (%i. b) A"
"\<Prod>i\<in>A. b" == "setprod (%i. b) A"
text{* Instead of @{term"\<Prod>x\<in>{x. P}. e"} we introduce the shorter
@{text"\<Prod>x|P. e"}. *}
syntax
"_qsetprod" :: "idt \<Rightarrow> bool \<Rightarrow> 'a \<Rightarrow> 'a" ("(3PROD _ |/ _./ _)" [0,0,10] 10)
syntax (xsymbols)
"_qsetprod" :: "idt \<Rightarrow> bool \<Rightarrow> 'a \<Rightarrow> 'a" ("(3\<Prod>_ | (_)./ _)" [0,0,10] 10)
syntax (HTML output)
"_qsetprod" :: "idt \<Rightarrow> bool \<Rightarrow> 'a \<Rightarrow> 'a" ("(3\<Prod>_ | (_)./ _)" [0,0,10] 10)
translations
"PROD x|P. t" => "setprod (%x. t) {x. P}"
"\<Prod>x|P. t" => "setprod (%x. t) {x. P}"
text{* Finally we abbreviate @{term"\<Prod>x\<in>A. x"} by @{text"\<Prod>A"}. *}
syntax
"_Setprod" :: "'a set => 'a::comm_monoid_mult" ("\<Prod>_" [1000] 999)
parse_translation {*
let
fun Setprod_tr [A] = Syntax.const "setprod" $ Abs ("", dummyT, Bound 0) $ A
in [("_Setprod", Setprod_tr)] end;
*}
print_translation {*
let fun setprod_tr' [Abs(x,Tx,t), A] =
if t = Bound 0 then Syntax.const "_Setprod" $ A else raise Match
in
[("setprod", setprod_tr')]
end
*}
lemma setprod_empty [simp]: "setprod f {} = 1"
by (auto simp add: setprod_def)
lemma setprod_insert [simp]: "[| finite A; a \<notin> A |] ==>
setprod f (insert a A) = f a * setprod f A"
by (simp add: setprod_def)
lemma setprod_infinite [simp]: "~ finite A ==> setprod f A = 1"
by (simp add: setprod_def)
lemma setprod_reindex:
"inj_on f B ==> setprod h (f ` B) = setprod (h \<circ> f) B"
by(auto simp: setprod_def AC_mult.fold_reindex dest!:finite_imageD)
lemma setprod_reindex_id: "inj_on f B ==> setprod f B = setprod id (f ` B)"
by (auto simp add: setprod_reindex)
lemma setprod_cong:
"A = B ==> (!!x. x:B ==> f x = g x) ==> setprod f A = setprod g B"
by(fastsimp simp: setprod_def intro: AC_mult.fold_cong)
lemma strong_setprod_cong:
"A = B ==> (!!x. x:B =simp=> f x = g x) ==> setprod f A = setprod g B"
by(fastsimp simp: simp_implies_def setprod_def intro: AC_mult.fold_cong)
lemma setprod_reindex_cong: "inj_on f A ==>
B = f ` A ==> g = h \<circ> f ==> setprod h B = setprod g A"
by (frule setprod_reindex, simp)
lemma setprod_1: "setprod (%i. 1) A = 1"
apply (case_tac "finite A")
apply (erule finite_induct, auto simp add: mult_ac)
done
lemma setprod_1': "ALL a:F. f a = 1 ==> setprod f F = 1"
apply (subgoal_tac "setprod f F = setprod (%x. 1) F")
apply (erule ssubst, rule setprod_1)
apply (rule setprod_cong, auto)
done
lemma setprod_Un_Int: "finite A ==> finite B
==> setprod g (A Un B) * setprod g (A Int B) = setprod g A * setprod g B"
by(simp add: setprod_def AC_mult.fold_Un_Int[symmetric])
lemma setprod_Un_disjoint: "finite A ==> finite B
==> A Int B = {} ==> setprod g (A Un B) = setprod g A * setprod g B"
by (subst setprod_Un_Int [symmetric], auto)
lemma setprod_UN_disjoint:
"finite I ==> (ALL i:I. finite (A i)) ==>
(ALL i:I. ALL j:I. i \<noteq> j --> A i Int A j = {}) ==>
setprod f (UNION I A) = setprod (%i. setprod f (A i)) I"
by(simp add: setprod_def AC_mult.fold_UN_disjoint cong: setprod_cong)
lemma setprod_Union_disjoint:
"[| (ALL A:C. finite A);
(ALL A:C. ALL B:C. A \<noteq> B --> A Int B = {}) |]
==> setprod f (Union C) = setprod (setprod f) C"
apply (cases "finite C")
prefer 2 apply (force dest: finite_UnionD simp add: setprod_def)
apply (frule setprod_UN_disjoint [of C id f])
apply (unfold Union_def id_def, assumption+)
done
lemma setprod_Sigma: "finite A ==> ALL x:A. finite (B x) ==>
(\<Prod>x\<in>A. (\<Prod>y\<in> B x. f x y)) =
(\<Prod>z\<in>(SIGMA x:A. B x). f (fst z) (snd z))"
by(simp add:setprod_def AC_mult.fold_Sigma split_def cong:setprod_cong)
text{*Here we can eliminate the finiteness assumptions, by cases.*}
lemma setprod_cartesian_product:
"(\<Prod>x\<in>A. (\<Prod>y\<in> B. f x y)) = (\<Prod>z\<in>(A <*> B). f (fst z) (snd z))"
apply (cases "finite A")
apply (cases "finite B")
apply (simp add: setprod_Sigma)
apply (cases "A={}", simp)
apply (simp add: setprod_1)
apply (auto simp add: setprod_def
dest: finite_cartesian_productD1 finite_cartesian_productD2)
done
lemma setprod_timesf:
"setprod (%x. f x * g x) A = (setprod f A * setprod g A)"
by(simp add:setprod_def AC_mult.fold_distrib)
subsubsection {* Properties in more restricted classes of structures *}
lemma setprod_eq_1_iff [simp]:
"finite F ==> (setprod f F = 1) = (ALL a:F. f a = (1::nat))"
by (induct set: Finites) auto
lemma setprod_zero:
"finite A ==> EX x: A. f x = (0::'a::comm_semiring_1_cancel) ==> setprod f A = 0"
apply (induct set: Finites, force, clarsimp)
apply (erule disjE, auto)
done
lemma setprod_nonneg [rule_format]:
"(ALL x: A. (0::'a::ordered_idom) \<le> f x) --> 0 \<le> setprod f A"
apply (case_tac "finite A")
apply (induct set: Finites, force, clarsimp)
apply (subgoal_tac "0 * 0 \<le> f x * setprod f F", force)
apply (rule mult_mono, assumption+)
apply (auto simp add: setprod_def)
done
lemma setprod_pos [rule_format]: "(ALL x: A. (0::'a::ordered_idom) < f x)
--> 0 < setprod f A"
apply (case_tac "finite A")
apply (induct set: Finites, force, clarsimp)
apply (subgoal_tac "0 * 0 < f x * setprod f F", force)
apply (rule mult_strict_mono, assumption+)
apply (auto simp add: setprod_def)
done
lemma setprod_nonzero [rule_format]:
"(ALL x y. (x::'a::comm_semiring_1_cancel) * y = 0 --> x = 0 | y = 0) ==>
finite A ==> (ALL x: A. f x \<noteq> (0::'a)) --> setprod f A \<noteq> 0"
apply (erule finite_induct, auto)
done
lemma setprod_zero_eq:
"(ALL x y. (x::'a::comm_semiring_1_cancel) * y = 0 --> x = 0 | y = 0) ==>
finite A ==> (setprod f A = (0::'a)) = (EX x: A. f x = 0)"
apply (insert setprod_zero [of A f] setprod_nonzero [of A f], blast)
done
lemma setprod_nonzero_field:
"finite A ==> (ALL x: A. f x \<noteq> (0::'a::field)) ==> setprod f A \<noteq> 0"
apply (rule setprod_nonzero, auto)
done
lemma setprod_zero_eq_field:
"finite A ==> (setprod f A = (0::'a::field)) = (EX x: A. f x = 0)"
apply (rule setprod_zero_eq, auto)
done
lemma setprod_Un: "finite A ==> finite B ==> (ALL x: A Int B. f x \<noteq> 0) ==>
(setprod f (A Un B) :: 'a ::{field})
= setprod f A * setprod f B / setprod f (A Int B)"
apply (subst setprod_Un_Int [symmetric], auto)
apply (subgoal_tac "finite (A Int B)")
apply (frule setprod_nonzero_field [of "A Int B" f], assumption)
apply (subst times_divide_eq_right [THEN sym], auto simp add: divide_self)
done
lemma setprod_diff1: "finite A ==> f a \<noteq> 0 ==>
(setprod f (A - {a}) :: 'a :: {field}) =
(if a:A then setprod f A / f a else setprod f A)"
apply (erule finite_induct)
apply (auto simp add: insert_Diff_if)
apply (subgoal_tac "f a * setprod f F / f a = setprod f F * f a / f a")
apply (erule ssubst)
apply (subst times_divide_eq_right [THEN sym])
apply (auto simp add: mult_ac times_divide_eq_right divide_self)
done
lemma setprod_inversef: "finite A ==>
ALL x: A. f x \<noteq> (0::'a::{field,division_by_zero}) ==>
setprod (inverse \<circ> f) A = inverse (setprod f A)"
apply (erule finite_induct)
apply (simp, simp)
done
lemma setprod_dividef:
"[|finite A;
\<forall>x \<in> A. g x \<noteq> (0::'a::{field,division_by_zero})|]
==> setprod (%x. f x / g x) A = setprod f A / setprod g A"
apply (subgoal_tac
"setprod (%x. f x / g x) A = setprod (%x. f x * (inverse \<circ> g) x) A")
apply (erule ssubst)
apply (subst divide_inverse)
apply (subst setprod_timesf)
apply (subst setprod_inversef, assumption+, rule refl)
apply (rule setprod_cong, rule refl)
apply (subst divide_inverse, auto)
done
subsection {* Finite cardinality *}
text {* This definition, although traditional, is ugly to work with:
@{text "card A == LEAST n. EX f. A = {f i | i. i < n}"}.
But now that we have @{text setsum} things are easy:
*}
constdefs
card :: "'a set => nat"
"card A == setsum (%x. 1::nat) A"
lemma card_empty [simp]: "card {} = 0"
by (simp add: card_def)
lemma card_infinite [simp]: "~ finite A ==> card A = 0"
by (simp add: card_def)
lemma card_eq_setsum: "card A = setsum (%x. 1) A"
by (simp add: card_def)
lemma card_insert_disjoint [simp]:
"finite A ==> x \<notin> A ==> card (insert x A) = Suc(card A)"
by(simp add: card_def)
lemma card_insert_if:
"finite A ==> card (insert x A) = (if x:A then card A else Suc(card(A)))"
by (simp add: insert_absorb)
lemma card_0_eq [simp]: "finite A ==> (card A = 0) = (A = {})"
apply auto
apply (drule_tac a = x in mk_disjoint_insert, clarify, auto)
done
lemma card_eq_0_iff: "(card A = 0) = (A = {} | ~ finite A)"
by auto
lemma card_Suc_Diff1: "finite A ==> x: A ==> Suc (card (A - {x})) = card A"
apply(rule_tac t = A in insert_Diff [THEN subst], assumption)
apply(simp del:insert_Diff_single)
done
lemma card_Diff_singleton:
"finite A ==> x: A ==> card (A - {x}) = card A - 1"
by (simp add: card_Suc_Diff1 [symmetric])
lemma card_Diff_singleton_if:
"finite A ==> card (A-{x}) = (if x : A then card A - 1 else card A)"
by (simp add: card_Diff_singleton)
lemma card_insert: "finite A ==> card (insert x A) = Suc (card (A - {x}))"
by (simp add: card_insert_if card_Suc_Diff1)
lemma card_insert_le: "finite A ==> card A <= card (insert x A)"
by (simp add: card_insert_if)
lemma card_mono: "\<lbrakk> finite B; A \<subseteq> B \<rbrakk> \<Longrightarrow> card A \<le> card B"
by (simp add: card_def setsum_mono2)
lemma card_seteq: "finite B ==> (!!A. A <= B ==> card B <= card A ==> A = B)"
apply (induct set: Finites, simp, clarify)
apply (subgoal_tac "finite A & A - {x} <= F")
prefer 2 apply (blast intro: finite_subset, atomize)
apply (drule_tac x = "A - {x}" in spec)
apply (simp add: card_Diff_singleton_if split add: split_if_asm)
apply (case_tac "card A", auto)
done
lemma psubset_card_mono: "finite B ==> A < B ==> card A < card B"
apply (simp add: psubset_def linorder_not_le [symmetric])
apply (blast dest: card_seteq)
done
lemma card_Un_Int: "finite A ==> finite B
==> card A + card B = card (A Un B) + card (A Int B)"
by(simp add:card_def setsum_Un_Int)
lemma card_Un_disjoint: "finite A ==> finite B
==> A Int B = {} ==> card (A Un B) = card A + card B"
by (simp add: card_Un_Int)
lemma card_Diff_subset:
"finite B ==> B <= A ==> card (A - B) = card A - card B"
by(simp add:card_def setsum_diff_nat)
lemma card_Diff1_less: "finite A ==> x: A ==> card (A - {x}) < card A"
apply (rule Suc_less_SucD)
apply (simp add: card_Suc_Diff1)
done
lemma card_Diff2_less:
"finite A ==> x: A ==> y: A ==> card (A - {x} - {y}) < card A"
apply (case_tac "x = y")
apply (simp add: card_Diff1_less)
apply (rule less_trans)
prefer 2 apply (auto intro!: card_Diff1_less)
done
lemma card_Diff1_le: "finite A ==> card (A - {x}) <= card A"
apply (case_tac "x : A")
apply (simp_all add: card_Diff1_less less_imp_le)
done
lemma card_psubset: "finite B ==> A \<subseteq> B ==> card A < card B ==> A < B"
by (erule psubsetI, blast)
lemma insert_partition:
"\<lbrakk> x \<notin> F; \<forall>c1 \<in> insert x F. \<forall>c2 \<in> insert x F. c1 \<noteq> c2 \<longrightarrow> c1 \<inter> c2 = {} \<rbrakk>
\<Longrightarrow> x \<inter> \<Union> F = {}"
by auto
(* main cardinality theorem *)
lemma card_partition [rule_format]:
"finite C ==>
finite (\<Union> C) -->
(\<forall>c\<in>C. card c = k) -->
(\<forall>c1 \<in> C. \<forall>c2 \<in> C. c1 \<noteq> c2 --> c1 \<inter> c2 = {}) -->
k * card(C) = card (\<Union> C)"
apply (erule finite_induct, simp)
apply (simp add: card_insert_disjoint card_Un_disjoint insert_partition
finite_subset [of _ "\<Union> (insert x F)"])
done
lemma setsum_constant [simp]: "(\<Sum>x \<in> A. y) = of_nat(card A) * y"
apply (cases "finite A")
apply (erule finite_induct)
apply (auto simp add: ring_distrib add_ac)
done
lemma setprod_constant: "finite A ==> (\<Prod>x\<in> A. (y::'a::recpower)) = y^(card A)"
apply (erule finite_induct)
apply (auto simp add: power_Suc)
done
lemma setsum_bounded:
assumes le: "\<And>i. i\<in>A \<Longrightarrow> f i \<le> (K::'a::{comm_semiring_1_cancel, pordered_ab_semigroup_add})"
shows "setsum f A \<le> of_nat(card A) * K"
proof (cases "finite A")
case True
thus ?thesis using le setsum_mono[where K=A and g = "%x. K"] by simp
next
case False thus ?thesis by (simp add: setsum_def)
qed
subsubsection {* Cardinality of unions *}
lemma of_nat_id[simp]: "(of_nat n :: nat) = n"
by(induct n, auto)
lemma card_UN_disjoint:
"finite I ==> (ALL i:I. finite (A i)) ==>
(ALL i:I. ALL j:I. i \<noteq> j --> A i Int A j = {}) ==>
card (UNION I A) = (\<Sum>i\<in>I. card(A i))"
apply (simp add: card_def del: setsum_constant)
apply (subgoal_tac
"setsum (%i. card (A i)) I = setsum (%i. (setsum (%x. 1) (A i))) I")
apply (simp add: setsum_UN_disjoint del: setsum_constant)
apply (simp cong: setsum_cong)
done
lemma card_Union_disjoint:
"finite C ==> (ALL A:C. finite A) ==>
(ALL A:C. ALL B:C. A \<noteq> B --> A Int B = {}) ==>
card (Union C) = setsum card C"
apply (frule card_UN_disjoint [of C id])
apply (unfold Union_def id_def, assumption+)
done
subsubsection {* Cardinality of image *}
text{*The image of a finite set can be expressed using @{term fold}.*}
lemma image_eq_fold: "finite A ==> f ` A = fold (op Un) (%x. {f x}) {} A"
apply (erule finite_induct, simp)
apply (subst ACf.fold_insert)
apply (auto simp add: ACf_def)
done
lemma card_image_le: "finite A ==> card (f ` A) <= card A"
apply (induct set: Finites, simp)
apply (simp add: le_SucI finite_imageI card_insert_if)
done
lemma card_image: "inj_on f A ==> card (f ` A) = card A"
by(simp add:card_def setsum_reindex o_def del:setsum_constant)
lemma endo_inj_surj: "finite A ==> f ` A \<subseteq> A ==> inj_on f A ==> f ` A = A"
by (simp add: card_seteq card_image)
lemma eq_card_imp_inj_on:
"[| finite A; card(f ` A) = card A |] ==> inj_on f A"
apply (induct rule:finite_induct, simp)
apply(frule card_image_le[where f = f])
apply(simp add:card_insert_if split:if_splits)
done
lemma inj_on_iff_eq_card:
"finite A ==> inj_on f A = (card(f ` A) = card A)"
by(blast intro: card_image eq_card_imp_inj_on)
lemma card_inj_on_le:
"[|inj_on f A; f ` A \<subseteq> B; finite B |] ==> card A \<le> card B"
apply (subgoal_tac "finite A")
apply (force intro: card_mono simp add: card_image [symmetric])
apply (blast intro: finite_imageD dest: finite_subset)
done
lemma card_bij_eq:
"[|inj_on f A; f ` A \<subseteq> B; inj_on g B; g ` B \<subseteq> A;
finite A; finite B |] ==> card A = card B"
by (auto intro: le_anti_sym card_inj_on_le)
subsubsection {* Cardinality of products *}
(*
lemma SigmaI_insert: "y \<notin> A ==>
(SIGMA x:(insert y A). B x) = (({y} <*> (B y)) \<union> (SIGMA x: A. B x))"
by auto
*)
lemma card_SigmaI [simp]:
"\<lbrakk> finite A; ALL a:A. finite (B a) \<rbrakk>
\<Longrightarrow> card (SIGMA x: A. B x) = (\<Sum>a\<in>A. card (B a))"
by(simp add:card_def setsum_Sigma del:setsum_constant)
lemma card_cartesian_product: "card (A <*> B) = card(A) * card(B)"
apply (cases "finite A")
apply (cases "finite B")
apply (auto simp add: card_eq_0_iff
dest: finite_cartesian_productD1 finite_cartesian_productD2)
done
lemma card_cartesian_product_singleton: "card({x} <*> A) = card(A)"
by (simp add: card_cartesian_product)
subsubsection {* Cardinality of the Powerset *}
lemma card_Pow: "finite A ==> card (Pow A) = Suc (Suc 0) ^ card A" (* FIXME numeral 2 (!?) *)
apply (induct set: Finites)
apply (simp_all add: Pow_insert)
apply (subst card_Un_disjoint, blast)
apply (blast intro: finite_imageI, blast)
apply (subgoal_tac "inj_on (insert x) (Pow F)")
apply (simp add: card_image Pow_insert)
apply (unfold inj_on_def)
apply (blast elim!: equalityE)
done
text {* Relates to equivalence classes. Based on a theorem of
F. Kammüller's. *}
lemma dvd_partition:
"finite (Union C) ==>
ALL c : C. k dvd card c ==>
(ALL c1: C. ALL c2: C. c1 \<noteq> c2 --> c1 Int c2 = {}) ==>
k dvd card (Union C)"
apply(frule finite_UnionD)
apply(rotate_tac -1)
apply (induct set: Finites, simp_all, clarify)
apply (subst card_Un_disjoint)
apply (auto simp add: dvd_add disjoint_eq_subset_Compl)
done
subsection{* A fold functional for non-empty sets *}
text{* Does not require start value. *}
consts
fold1Set :: "('a => 'a => 'a) => ('a set \<times> 'a) set"
inductive "fold1Set f"
intros
fold1Set_insertI [intro]:
"\<lbrakk> (A,x) \<in> foldSet f id a; a \<notin> A \<rbrakk> \<Longrightarrow> (insert a A, x) \<in> fold1Set f"
constdefs
fold1 :: "('a => 'a => 'a) => 'a set => 'a"
"fold1 f A == THE x. (A, x) : fold1Set f"
lemma fold1Set_nonempty:
"(A, x) : fold1Set f \<Longrightarrow> A \<noteq> {}"
by(erule fold1Set.cases, simp_all)
inductive_cases empty_fold1SetE [elim!]: "({}, x) : fold1Set f"
inductive_cases insert_fold1SetE [elim!]: "(insert a X, x) : fold1Set f"
lemma fold1Set_sing [iff]: "(({a},b) : fold1Set f) = (a = b)"
by (blast intro: foldSet.intros elim: foldSet.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. (A, x) : fold1Set f"
apply (induct A rule: finite_induct)
apply (auto dest: finite_imp_foldSet [of _ f id])
done
text{*First, some lemmas about @{term foldSet}.*}
lemma (in ACf) foldSet_insert_swap:
assumes fold: "(A,y) \<in> foldSet f id b"
shows "b \<notin> A \<Longrightarrow> (insert b A, z \<cdot> y) \<in> foldSet f id z"
using fold
proof (induct rule: foldSet.induct)
case emptyI thus ?case by (force simp add: fold_insert_aux commute)
next
case (insertI A x y)
have "(insert x (insert b A), x \<cdot> (z \<cdot> y)) \<in> foldSet f (\<lambda>u. u) z"
using insertI by force --{*how does @{term id} get unfolded?*}
thus ?case by (simp add: insert_commute AC)
qed
lemma (in ACf) foldSet_permute_diff:
assumes fold: "(A,x) \<in> foldSet f id b"
shows "!!a. \<lbrakk>a \<in> A; b \<notin> A\<rbrakk> \<Longrightarrow> (insert b (A-{a}), x) \<in> foldSet f id a"
using fold
proof (induct rule: foldSet.induct)
case emptyI thus ?case by simp
next
case (insertI A x 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: foldSet_insert_swap)
next
assume ainA: "a \<in> A"
hence "(insert x (insert b (A - {a})), x \<cdot> y) \<in> foldSet f id a"
using insertI by (force simp: id_def)
moreover
have "insert x (insert b (A - {a})) = insert b (insert x A - {a})"
using ainA insertI by blast
ultimately show ?thesis by (simp add: id_def)
qed
qed
lemma (in ACf) fold1_eq_fold:
"[|finite A; a \<notin> A|] ==> fold1 f (insert a A) = fold f id a A"
apply (simp add: fold1_def fold_def)
apply (rule the_equality)
apply (best intro: foldSet_determ theI dest: finite_imp_foldSet [of _ f id])
apply (rule sym, clarify)
apply (case_tac "Aa=A")
apply (best intro: the_equality foldSet_determ)
apply (subgoal_tac "(A,x) \<in> foldSet f id a")
apply (best intro: the_equality foldSet_determ)
apply (subgoal_tac "insert aa (Aa - {a}) = A")
prefer 2 apply (blast elim: equalityE)
apply (auto dest: foldSet_permute_diff [where a=a])
done
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 (in ACf) fold1_insert:
assumes nonempty: "A \<noteq> {}" and A: "finite A" "x \<notin> A"
shows "fold1 f (insert x A) = f x (fold1 f A)"
proof -
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
lemma (in ACIf) fold1_insert_idem [simp]:
assumes nonempty: "A \<noteq> {}" and A: "finite A"
shows "fold1 f (insert x A) = f x (fold1 f A)"
proof -
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 add: idem)
next
assume "A' \<noteq> {}"
with prems show ?thesis
by (simp add: fold1_insert assoc [symmetric] idem)
qed
next
assume "a \<noteq> x"
with prems show ?thesis
by (simp add: insert_commute fold1_eq_fold fold_insert_idem)
qed
qed
text{* Now the recursion rules for definitions: *}
lemma fold1_singleton_def: "g \<equiv> fold1 f \<Longrightarrow> g {a} = a"
by(simp add:fold1_singleton)
lemma (in ACf) fold1_insert_def:
"\<lbrakk> g \<equiv> fold1 f; finite A; x \<notin> A; A \<noteq> {} \<rbrakk> \<Longrightarrow> g(insert x A) = x \<cdot> (g A)"
by(simp add:fold1_insert)
lemma (in ACIf) fold1_insert_idem_def:
"\<lbrakk> g \<equiv> fold1 f; finite A; A \<noteq> {} \<rbrakk> \<Longrightarrow> g(insert x A) = x \<cdot> (g A)"
by(simp add:fold1_insert_idem)
subsubsection{* Determinacy for @{term fold1Set} *}
text{*Not actually used!!*}
lemma (in ACf) foldSet_permute:
"[|(insert a A, x) \<in> foldSet f id b; a \<notin> A; b \<notin> A|]
==> (insert b A, x) \<in> foldSet f id a"
apply (case_tac "a=b")
apply (auto dest: foldSet_permute_diff)
done
lemma (in ACf) fold1Set_determ:
"(A, x) \<in> fold1Set f ==> (A, y) \<in> fold1Set f ==> y = x"
proof (clarify elim!: fold1Set.cases)
fix A x B y a b
assume Ax: "(A, x) \<in> foldSet f id a"
assume By: "(B, y) \<in> foldSet f id b"
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: foldSet_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 "(insert b ?D, y) \<in> foldSet f id a"
by (auto intro: foldSet_permute simp add: insert_absorb)
moreover
have "(insert b ?D, x) \<in> foldSet f id a"
by (simp add: A [symmetric] Ax)
ultimately show ?thesis by (blast intro: foldSet_determ)
qed
qed
lemma (in ACf) fold1Set_equality: "(A, y) : fold1Set f ==> fold1 f A = y"
by (unfold fold1_def) (blast intro: fold1Set_determ)
declare
empty_foldSetE [rule del] foldSet.intros [rule del]
empty_fold1SetE [rule del] insert_fold1SetE [rule del]
-- {* No more proves involve these relations. *}
subsubsection{* Semi-Lattices *}
locale ACIfSL = ACIf +
fixes below :: "'a \<Rightarrow> 'a \<Rightarrow> bool" (infixl "\<sqsubseteq>" 50)
assumes below_def: "(x \<sqsubseteq> y) = (x\<cdot>y = x)"
locale ACIfSLlin = ACIfSL +
assumes lin: "x\<cdot>y \<in> {x,y}"
lemma (in ACIfSL) below_refl[simp]: "x \<sqsubseteq> x"
by(simp add: below_def idem)
lemma (in ACIfSL) below_f_conv[simp]: "x \<sqsubseteq> y \<cdot> z = (x \<sqsubseteq> y \<and> x \<sqsubseteq> z)"
proof
assume "x \<sqsubseteq> y \<cdot> z"
hence xyzx: "x \<cdot> (y \<cdot> z) = x" by(simp add: below_def)
have "x \<cdot> y = x"
proof -
have "x \<cdot> y = (x \<cdot> (y \<cdot> z)) \<cdot> y" by(rule subst[OF xyzx], rule refl)
also have "\<dots> = x \<cdot> (y \<cdot> z)" by(simp add:ACI)
also have "\<dots> = x" by(rule xyzx)
finally show ?thesis .
qed
moreover have "x \<cdot> z = x"
proof -
have "x \<cdot> z = (x \<cdot> (y \<cdot> z)) \<cdot> z" by(rule subst[OF xyzx], rule refl)
also have "\<dots> = x \<cdot> (y \<cdot> z)" by(simp add:ACI)
also have "\<dots> = x" by(rule xyzx)
finally show ?thesis .
qed
ultimately show "x \<sqsubseteq> y \<and> x \<sqsubseteq> z" by(simp add: below_def)
next
assume a: "x \<sqsubseteq> y \<and> x \<sqsubseteq> z"
hence y: "x \<cdot> y = x" and z: "x \<cdot> z = x" by(simp_all add: below_def)
have "x \<cdot> (y \<cdot> z) = (x \<cdot> y) \<cdot> z" by(simp add:assoc)
also have "x \<cdot> y = x" using a by(simp_all add: below_def)
also have "x \<cdot> z = x" using a by(simp_all add: below_def)
finally show "x \<sqsubseteq> y \<cdot> z" by(simp_all add: below_def)
qed
lemma (in ACIfSLlin) above_f_conv:
"x \<cdot> y \<sqsubseteq> z = (x \<sqsubseteq> z \<or> y \<sqsubseteq> z)"
proof
assume a: "x \<cdot> y \<sqsubseteq> z"
have "x \<cdot> y = x \<or> x \<cdot> y = y" using lin[of x y] by simp
thus "x \<sqsubseteq> z \<or> y \<sqsubseteq> z"
proof
assume "x \<cdot> y = x" hence "x \<sqsubseteq> z" by(rule subst)(rule a) thus ?thesis ..
next
assume "x \<cdot> y = y" hence "y \<sqsubseteq> z" by(rule subst)(rule a) thus ?thesis ..
qed
next
assume "x \<sqsubseteq> z \<or> y \<sqsubseteq> z"
thus "x \<cdot> y \<sqsubseteq> z"
proof
assume a: "x \<sqsubseteq> z"
have "(x \<cdot> y) \<cdot> z = (x \<cdot> z) \<cdot> y" by(simp add:ACI)
also have "x \<cdot> z = x" using a by(simp add:below_def)
finally show "x \<cdot> y \<sqsubseteq> z" by(simp add:below_def)
next
assume a: "y \<sqsubseteq> z"
have "(x \<cdot> y) \<cdot> z = x \<cdot> (y \<cdot> z)" by(simp add:ACI)
also have "y \<cdot> z = y" using a by(simp add:below_def)
finally show "x \<cdot> y \<sqsubseteq> z" by(simp add:below_def)
qed
qed
subsubsection{* Lemmas about @{text fold1} *}
lemma (in ACf) fold1_Un:
assumes A: "finite A" "A \<noteq> {}"
shows "finite B \<Longrightarrow> B \<noteq> {} \<Longrightarrow> A Int B = {} \<Longrightarrow>
fold1 f (A Un B) = f (fold1 f A) (fold1 f B)"
using A
proof(induct rule:finite_ne_induct)
case singleton thus ?case by(simp add:fold1_insert)
next
case insert thus ?case by (simp add:fold1_insert assoc)
qed
lemma (in ACIf) fold1_Un2:
assumes A: "finite A" "A \<noteq> {}"
shows "finite B \<Longrightarrow> B \<noteq> {} \<Longrightarrow>
fold1 f (A Un B) = f (fold1 f A) (fold1 f B)"
using A
proof(induct rule:finite_ne_induct)
case singleton thus ?case by(simp add:fold1_insert_idem)
next
case insert thus ?case by (simp add:fold1_insert_idem assoc)
qed
lemma (in ACf) fold1_in:
assumes A: "finite (A)" "A \<noteq> {}" and elem: "\<And>x y. x\<cdot>y \<in> {x,y}"
shows "fold1 f 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
lemma (in ACIfSL) below_fold1_iff:
assumes A: "finite A" "A \<noteq> {}"
shows "x \<sqsubseteq> fold1 f A = (\<forall>a\<in>A. x \<sqsubseteq> a)"
using A
by(induct rule:finite_ne_induct) simp_all
lemma (in ACIfSL) fold1_belowI:
assumes A: "finite A" "A \<noteq> {}"
shows "a \<in> A \<Longrightarrow> fold1 f A \<sqsubseteq> a"
using A
proof (induct rule:finite_ne_induct)
case singleton thus ?case by simp
next
case (insert x F)
from insert(5) have "a = x \<or> a \<in> F" by simp
thus ?case
proof
assume "a = x" thus ?thesis using insert by(simp add:below_def ACI)
next
assume "a \<in> F"
hence bel: "fold1 f F \<sqsubseteq> a" by(rule insert)
have "fold1 f (insert x F) \<cdot> a = x \<cdot> (fold1 f F \<cdot> a)"
using insert by(simp add:below_def ACI)
also have "fold1 f F \<cdot> a = fold1 f F"
using bel by(simp add:below_def ACI)
also have "x \<cdot> \<dots> = fold1 f (insert x F)"
using insert by(simp add:below_def ACI)
finally show ?thesis by(simp add:below_def)
qed
qed
lemma (in ACIfSLlin) fold1_below_iff:
assumes A: "finite A" "A \<noteq> {}"
shows "fold1 f A \<sqsubseteq> x = (\<exists>a\<in>A. a \<sqsubseteq> x)"
using A
by(induct rule:finite_ne_induct)(simp_all add:above_f_conv)
subsubsection{* Lattices *}
locale Lattice = lattice +
fixes Inf :: "'a set \<Rightarrow> 'a" ("\<Sqinter>_" [900] 900)
and Sup :: "'a set \<Rightarrow> 'a" ("\<Squnion>_" [900] 900)
defines "Inf == fold1 inf" and "Sup == fold1 sup"
locale Distrib_Lattice = distrib_lattice + Lattice
text{* Lattices are semilattices *}
lemma (in Lattice) ACf_inf: "ACf inf"
by(blast intro: ACf.intro inf_commute inf_assoc)
lemma (in Lattice) ACf_sup: "ACf sup"
by(blast intro: ACf.intro sup_commute sup_assoc)
lemma (in Lattice) ACIf_inf: "ACIf inf"
apply(rule ACIf.intro)
apply(rule ACf_inf)
apply(rule ACIf_axioms.intro)
apply(rule inf_idem)
done
lemma (in Lattice) ACIf_sup: "ACIf sup"
apply(rule ACIf.intro)
apply(rule ACf_sup)
apply(rule ACIf_axioms.intro)
apply(rule sup_idem)
done
lemma (in Lattice) ACIfSL_inf: "ACIfSL inf (op \<sqsubseteq>)"
apply(rule ACIfSL.intro)
apply(rule ACf_inf)
apply(rule ACIf.axioms[OF ACIf_inf])
apply(rule ACIfSL_axioms.intro)
apply(rule iffI)
apply(blast intro: antisym inf_le1 inf_le2 inf_least refl)
apply(erule subst)
apply(rule inf_le2)
done
lemma (in Lattice) ACIfSL_sup: "ACIfSL sup (%x y. y \<sqsubseteq> x)"
apply(rule ACIfSL.intro)
apply(rule ACf_sup)
apply(rule ACIf.axioms[OF ACIf_sup])
apply(rule ACIfSL_axioms.intro)
apply(rule iffI)
apply(blast intro: antisym sup_ge1 sup_ge2 sup_greatest refl)
apply(erule subst)
apply(rule sup_ge2)
done
subsubsection{* Fold laws in lattices *}
lemma (in Lattice) Inf_le_Sup[simp]: "\<lbrakk> finite A; A \<noteq> {} \<rbrakk> \<Longrightarrow> \<Sqinter>A \<sqsubseteq> \<Squnion>A"
apply(unfold Sup_def Inf_def)
apply(subgoal_tac "EX a. a:A")
prefer 2 apply blast
apply(erule exE)
apply(rule trans)
apply(erule (2) ACIfSL.fold1_belowI[OF ACIfSL_inf])
apply(erule (2) ACIfSL.fold1_belowI[OF ACIfSL_sup])
done
lemma (in Lattice) sup_Inf_absorb[simp]:
"\<lbrakk> finite A; A \<noteq> {}; a \<in> A \<rbrakk> \<Longrightarrow> (a \<squnion> \<Sqinter>A) = a"
apply(subst sup_commute)
apply(simp add:Inf_def sup_absorb ACIfSL.fold1_belowI[OF ACIfSL_inf])
done
lemma (in Lattice) inf_Sup_absorb[simp]:
"\<lbrakk> finite A; A \<noteq> {}; a \<in> A \<rbrakk> \<Longrightarrow> (a \<sqinter> \<Squnion>A) = a"
by(simp add:Sup_def inf_absorb ACIfSL.fold1_belowI[OF ACIfSL_sup])
lemma (in Distrib_Lattice) sup_Inf1_distrib:
assumes A: "finite A" "A \<noteq> {}"
shows "(x \<squnion> \<Sqinter>A) = \<Sqinter>{x \<squnion> a|a. a \<in> A}"
using A
proof (induct rule: finite_ne_induct)
case singleton thus ?case by(simp add:Inf_def)
next
case (insert y A)
have fin: "finite {x \<squnion> a |a. a \<in> A}"
by(fast intro: finite_surj[where f = "%a. x \<squnion> a", OF insert(1)])
have "x \<squnion> \<Sqinter> (insert y A) = x \<squnion> (y \<sqinter> \<Sqinter> A)"
using insert by(simp add:ACf.fold1_insert_def[OF ACf_inf Inf_def])
also have "\<dots> = (x \<squnion> y) \<sqinter> (x \<squnion> \<Sqinter> A)" by(rule sup_inf_distrib1)
also have "x \<squnion> \<Sqinter> A = \<Sqinter>{x \<squnion> a|a. a \<in> A}" using insert by simp
also have "(x \<squnion> y) \<sqinter> \<dots> = \<Sqinter> (insert (x \<squnion> y) {x \<squnion> a |a. a \<in> A})"
using insert by(simp add:ACIf.fold1_insert_idem_def[OF ACIf_inf Inf_def fin])
also have "insert (x\<squnion>y) {x\<squnion>a |a. a \<in> A} = {x\<squnion>a |a. a \<in> insert y A}"
by blast
finally show ?case .
qed
lemma (in Distrib_Lattice) sup_Inf2_distrib:
assumes A: "finite A" "A \<noteq> {}" and B: "finite B" "B \<noteq> {}"
shows "(\<Sqinter>A \<squnion> \<Sqinter>B) = \<Sqinter>{a \<squnion> b|a b. a \<in> A \<and> b \<in> B}"
using A
proof (induct rule: finite_ne_induct)
case singleton thus ?case
by(simp add: sup_Inf1_distrib[OF B] fold1_singleton_def[OF Inf_def])
next
case (insert x A)
have finB: "finite {x \<squnion> b |b. b \<in> B}"
by(fast intro: finite_surj[where f = "%b. x \<squnion> b", OF B(1)])
have finAB: "finite {a \<squnion> b |a b. a \<in> A \<and> b \<in> B}"
proof -
have "{a \<squnion> b |a b. a \<in> A \<and> b \<in> B} = (UN a:A. UN b:B. {a \<squnion> b})"
by blast
thus ?thesis by(simp add: insert(1) B(1))
qed
have ne: "{a \<squnion> b |a b. a \<in> A \<and> b \<in> B} \<noteq> {}" using insert B by blast
have "\<Sqinter>(insert x A) \<squnion> \<Sqinter>B = (x \<sqinter> \<Sqinter>A) \<squnion> \<Sqinter>B"
using insert by(simp add:ACIf.fold1_insert_idem_def[OF ACIf_inf Inf_def])
also have "\<dots> = (x \<squnion> \<Sqinter>B) \<sqinter> (\<Sqinter>A \<squnion> \<Sqinter>B)" by(rule sup_inf_distrib2)
also have "\<dots> = \<Sqinter>{x \<squnion> b|b. b \<in> B} \<sqinter> \<Sqinter>{a \<squnion> b|a b. a \<in> A \<and> b \<in> B}"
using insert by(simp add:sup_Inf1_distrib[OF B])
also have "\<dots> = \<Sqinter>({x\<squnion>b |b. b \<in> B} \<union> {a\<squnion>b |a b. a \<in> A \<and> b \<in> B})"
(is "_ = \<Sqinter>?M")
using B insert
by(simp add:Inf_def ACIf.fold1_Un2[OF ACIf_inf finB _ finAB ne])
also have "?M = {a \<squnion> b |a b. a \<in> insert x A \<and> b \<in> B}"
by blast
finally show ?case .
qed
subsection{*Min and Max*}
text{* As an application of @{text fold1} we define the minimal and
maximal element of a (non-empty) set over a linear order. *}
constdefs
Min :: "('a::linorder)set => 'a"
"Min == fold1 min"
Max :: "('a::linorder)set => 'a"
"Max == fold1 max"
text{* Before we can do anything, we need to show that @{text min} and
@{text max} are ACI and the ordering is linear: *}
interpretation min: ACf ["min:: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a"]
apply(rule ACf.intro)
apply(auto simp:min_def)
done
interpretation min: ACIf ["min:: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a"]
apply(rule ACIf_axioms.intro)
apply(auto simp:min_def)
done
interpretation max: ACf ["max :: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a"]
apply(rule ACf.intro)
apply(auto simp:max_def)
done
interpretation max: ACIf ["max:: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a"]
apply(rule ACIf_axioms.intro)
apply(auto simp:max_def)
done
interpretation min:
ACIfSL ["min:: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a" "op \<le>"]
apply(rule ACIfSL_axioms.intro)
apply(auto simp:min_def)
done
interpretation min:
ACIfSLlin ["min :: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a" "op \<le>"]
apply(rule ACIfSLlin_axioms.intro)
apply(auto simp:min_def)
done
interpretation max:
ACIfSL ["max :: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a" "%x y. y\<le>x"]
apply(rule ACIfSL_axioms.intro)
apply(auto simp:max_def)
done
interpretation max:
ACIfSLlin ["max :: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a" "%x y. y\<le>x"]
apply(rule ACIfSLlin_axioms.intro)
apply(auto simp:max_def)
done
interpretation min_max:
Lattice ["op \<le>" "min :: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a" "max" "Min" "Max"]
apply -
apply(rule Min_def)
apply(rule Max_def)
done
interpretation min_max:
Distrib_Lattice ["op \<le>" "min :: 'a::linorder \<Rightarrow> 'a \<Rightarrow> 'a" "max" "Min" "Max"]
.
text{* Now we instantiate the recursion equations and declare them
simplification rules: *}
(* Making Min or Max a defined parameter of a locale, suitably
extending ACIf, could make the following interpretations more automatic. *)
lemmas Min_singleton = fold1_singleton_def [OF Min_def]
lemmas Max_singleton = fold1_singleton_def [OF Max_def]
lemmas Min_insert = min.fold1_insert_idem_def [OF Min_def]
lemmas Max_insert = max.fold1_insert_idem_def [OF Max_def]
declare Min_singleton [simp] Max_singleton [simp]
declare Min_insert [simp] Max_insert [simp]
text{* Now we instantiate some @{text fold1} properties: *}
lemma Min_in [simp]:
shows "finite A \<Longrightarrow> A \<noteq> {} \<Longrightarrow> Min A \<in> A"
using min.fold1_in
by(fastsimp simp: Min_def min_def)
lemma Max_in [simp]:
shows "finite A \<Longrightarrow> A \<noteq> {} \<Longrightarrow> Max A \<in> A"
using max.fold1_in
by(fastsimp simp: Max_def max_def)
lemma Min_le [simp]: "\<lbrakk> finite A; A \<noteq> {}; x \<in> A \<rbrakk> \<Longrightarrow> Min A \<le> x"
by(simp add: Min_def min.fold1_belowI)
lemma Max_ge [simp]: "\<lbrakk> finite A; A \<noteq> {}; x \<in> A \<rbrakk> \<Longrightarrow> x \<le> Max A"
by(simp add: Max_def max.fold1_belowI)
lemma Min_ge_iff[simp]:
"\<lbrakk> finite A; A \<noteq> {} \<rbrakk> \<Longrightarrow> (x \<le> Min A) = (\<forall>a\<in>A. x \<le> a)"
by(simp add: Min_def min.below_fold1_iff)
lemma Max_le_iff[simp]:
"\<lbrakk> finite A; A \<noteq> {} \<rbrakk> \<Longrightarrow> (Max A \<le> x) = (\<forall>a\<in>A. a \<le> x)"
by(simp add: Max_def max.below_fold1_iff)
lemma Min_le_iff:
"\<lbrakk> finite A; A \<noteq> {} \<rbrakk> \<Longrightarrow> (Min A \<le> x) = (\<exists>a\<in>A. a \<le> x)"
by(simp add: Min_def min.fold1_below_iff)
lemma Max_ge_iff:
"\<lbrakk> finite A; A \<noteq> {} \<rbrakk> \<Longrightarrow> (x \<le> Max A) = (\<exists>a\<in>A. x \<le> a)"
by(simp add: Max_def max.fold1_below_iff)
subsection {* Properties of axclass @{text finite} *}
text{* Many of these are by Brian Huffman. *}
lemma finite_set: "finite (A::'a::finite set)"
by (rule finite_subset [OF subset_UNIV finite])
instance unit :: finite
proof
have "finite {()}" by simp
also have "{()} = UNIV" by auto
finally show "finite (UNIV :: unit set)" .
qed
instance bool :: finite
proof
have "finite {True, False}" by simp
also have "{True, False} = UNIV" by auto
finally show "finite (UNIV :: bool set)" .
qed
instance * :: (finite, finite) finite
proof
show "finite (UNIV :: ('a \<times> 'b) set)"
proof (rule finite_Prod_UNIV)
show "finite (UNIV :: 'a set)" by (rule finite)
show "finite (UNIV :: 'b set)" by (rule finite)
qed
qed
instance "+" :: (finite, finite) finite
proof
have a: "finite (UNIV :: 'a set)" by (rule finite)
have b: "finite (UNIV :: 'b set)" by (rule finite)
from a b have "finite ((UNIV :: 'a set) <+> (UNIV :: 'b set))"
by (rule finite_Plus)
thus "finite (UNIV :: ('a + 'b) set)" by simp
qed
instance set :: (finite) finite
proof
have "finite (UNIV :: 'a set)" by (rule finite)
hence "finite (Pow (UNIV :: 'a set))"
by (rule finite_Pow_iff [THEN iffD2])
thus "finite (UNIV :: 'a set set)" by simp
qed
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}"
show "finite (range ?graph)" by (rule finite_set)
show "inj ?graph" by (rule inj_graph)
qed
qed
end