src/HOL/Library/Extended_Nat.thy
changeset 43919 a7e4fb1a0502
parent 43532 d32d72ea3215
child 43921 e8511be08ddd
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/HOL/Library/Extended_Nat.thy	Tue Jul 19 14:35:44 2011 +0200
@@ -0,0 +1,551 @@
+(*  Title:      HOL/Library/Extended_Nat.thy
+    Author:     David von Oheimb, TU Muenchen;  Florian Haftmann, TU Muenchen
+    Contributions: David Trachtenherz, TU Muenchen
+*)
+
+header {* Extended natural numbers (i.e. with infinity) *}
+
+theory Extended_Nat
+imports Main
+begin
+
+subsection {* Type definition *}
+
+text {*
+  We extend the standard natural numbers by a special value indicating
+  infinity.
+*}
+
+datatype enat = Fin nat | Infty
+
+notation (xsymbols)
+  Infty  ("\<infinity>")
+
+notation (HTML output)
+  Infty  ("\<infinity>")
+
+
+lemma not_Infty_eq[iff]: "(x ~= Infty) = (EX i. x = Fin i)"
+by (cases x) auto
+
+lemma not_Fin_eq [iff]: "(ALL y. x ~= Fin y) = (x = Infty)"
+by (cases x) auto
+
+
+primrec the_Fin :: "enat \<Rightarrow> nat"
+where "the_Fin (Fin n) = n"
+
+
+subsection {* Constructors and numbers *}
+
+instantiation enat :: "{zero, one, number}"
+begin
+
+definition
+  "0 = Fin 0"
+
+definition
+  [code_unfold]: "1 = Fin 1"
+
+definition
+  [code_unfold, code del]: "number_of k = Fin (number_of k)"
+
+instance ..
+
+end
+
+definition iSuc :: "enat \<Rightarrow> enat" where
+  "iSuc i = (case i of Fin n \<Rightarrow> Fin (Suc n) | \<infinity> \<Rightarrow> \<infinity>)"
+
+lemma Fin_0: "Fin 0 = 0"
+  by (simp add: zero_enat_def)
+
+lemma Fin_1: "Fin 1 = 1"
+  by (simp add: one_enat_def)
+
+lemma Fin_number: "Fin (number_of k) = number_of k"
+  by (simp add: number_of_enat_def)
+
+lemma one_iSuc: "1 = iSuc 0"
+  by (simp add: zero_enat_def one_enat_def iSuc_def)
+
+lemma Infty_ne_i0 [simp]: "\<infinity> \<noteq> 0"
+  by (simp add: zero_enat_def)
+
+lemma i0_ne_Infty [simp]: "0 \<noteq> \<infinity>"
+  by (simp add: zero_enat_def)
+
+lemma zero_enat_eq [simp]:
+  "number_of k = (0\<Colon>enat) \<longleftrightarrow> number_of k = (0\<Colon>nat)"
+  "(0\<Colon>enat) = number_of k \<longleftrightarrow> number_of k = (0\<Colon>nat)"
+  unfolding zero_enat_def number_of_enat_def by simp_all
+
+lemma one_enat_eq [simp]:
+  "number_of k = (1\<Colon>enat) \<longleftrightarrow> number_of k = (1\<Colon>nat)"
+  "(1\<Colon>enat) = number_of k \<longleftrightarrow> number_of k = (1\<Colon>nat)"
+  unfolding one_enat_def number_of_enat_def by simp_all
+
+lemma zero_one_enat_neq [simp]:
+  "\<not> 0 = (1\<Colon>enat)"
+  "\<not> 1 = (0\<Colon>enat)"
+  unfolding zero_enat_def one_enat_def by simp_all
+
+lemma Infty_ne_i1 [simp]: "\<infinity> \<noteq> 1"
+  by (simp add: one_enat_def)
+
+lemma i1_ne_Infty [simp]: "1 \<noteq> \<infinity>"
+  by (simp add: one_enat_def)
+
+lemma Infty_ne_number [simp]: "\<infinity> \<noteq> number_of k"
+  by (simp add: number_of_enat_def)
+
+lemma number_ne_Infty [simp]: "number_of k \<noteq> \<infinity>"
+  by (simp add: number_of_enat_def)
+
+lemma iSuc_Fin: "iSuc (Fin n) = Fin (Suc n)"
+  by (simp add: iSuc_def)
+
+lemma iSuc_number_of: "iSuc (number_of k) = Fin (Suc (number_of k))"
+  by (simp add: iSuc_Fin number_of_enat_def)
+
+lemma iSuc_Infty [simp]: "iSuc \<infinity> = \<infinity>"
+  by (simp add: iSuc_def)
+
+lemma iSuc_ne_0 [simp]: "iSuc n \<noteq> 0"
+  by (simp add: iSuc_def zero_enat_def split: enat.splits)
+
+lemma zero_ne_iSuc [simp]: "0 \<noteq> iSuc n"
+  by (rule iSuc_ne_0 [symmetric])
+
+lemma iSuc_inject [simp]: "iSuc m = iSuc n \<longleftrightarrow> m = n"
+  by (simp add: iSuc_def split: enat.splits)
+
+lemma number_of_enat_inject [simp]:
+  "(number_of k \<Colon> enat) = number_of l \<longleftrightarrow> (number_of k \<Colon> nat) = number_of l"
+  by (simp add: number_of_enat_def)
+
+
+subsection {* Addition *}
+
+instantiation enat :: comm_monoid_add
+begin
+
+definition [nitpick_simp]:
+  "m + n = (case m of \<infinity> \<Rightarrow> \<infinity> | Fin m \<Rightarrow> (case n of \<infinity> \<Rightarrow> \<infinity> | Fin n \<Rightarrow> Fin (m + n)))"
+
+lemma plus_enat_simps [simp, code]:
+  "Fin m + Fin n = Fin (m + n)"
+  "\<infinity> + q = \<infinity>"
+  "q + \<infinity> = \<infinity>"
+  by (simp_all add: plus_enat_def split: enat.splits)
+
+instance proof
+  fix n m q :: enat
+  show "n + m + q = n + (m + q)"
+    by (cases n, auto, cases m, auto, cases q, auto)
+  show "n + m = m + n"
+    by (cases n, auto, cases m, auto)
+  show "0 + n = n"
+    by (cases n) (simp_all add: zero_enat_def)
+qed
+
+end
+
+lemma plus_enat_0 [simp]:
+  "0 + (q\<Colon>enat) = q"
+  "(q\<Colon>enat) + 0 = q"
+  by (simp_all add: plus_enat_def zero_enat_def split: enat.splits)
+
+lemma plus_enat_number [simp]:
+  "(number_of k \<Colon> enat) + number_of l = (if k < Int.Pls then number_of l
+    else if l < Int.Pls then number_of k else number_of (k + l))"
+  unfolding number_of_enat_def plus_enat_simps nat_arith(1) if_distrib [symmetric, of _ Fin] ..
+
+lemma iSuc_number [simp]:
+  "iSuc (number_of k) = (if neg (number_of k \<Colon> int) then 1 else number_of (Int.succ k))"
+  unfolding iSuc_number_of
+  unfolding one_enat_def number_of_enat_def Suc_nat_number_of if_distrib [symmetric] ..
+
+lemma iSuc_plus_1:
+  "iSuc n = n + 1"
+  by (cases n) (simp_all add: iSuc_Fin one_enat_def)
+  
+lemma plus_1_iSuc:
+  "1 + q = iSuc q"
+  "q + 1 = iSuc q"
+by (simp_all add: iSuc_plus_1 add_ac)
+
+lemma iadd_Suc: "iSuc m + n = iSuc (m + n)"
+by (simp_all add: iSuc_plus_1 add_ac)
+
+lemma iadd_Suc_right: "m + iSuc n = iSuc (m + n)"
+by (simp only: add_commute[of m] iadd_Suc)
+
+lemma iadd_is_0: "(m + n = (0::enat)) = (m = 0 \<and> n = 0)"
+by (cases m, cases n, simp_all add: zero_enat_def)
+
+subsection {* Multiplication *}
+
+instantiation enat :: comm_semiring_1
+begin
+
+definition times_enat_def [nitpick_simp]:
+  "m * n = (case m of \<infinity> \<Rightarrow> if n = 0 then 0 else \<infinity> | Fin m \<Rightarrow>
+    (case n of \<infinity> \<Rightarrow> if m = 0 then 0 else \<infinity> | Fin n \<Rightarrow> Fin (m * n)))"
+
+lemma times_enat_simps [simp, code]:
+  "Fin m * Fin n = Fin (m * n)"
+  "\<infinity> * \<infinity> = \<infinity>"
+  "\<infinity> * Fin n = (if n = 0 then 0 else \<infinity>)"
+  "Fin m * \<infinity> = (if m = 0 then 0 else \<infinity>)"
+  unfolding times_enat_def zero_enat_def
+  by (simp_all split: enat.split)
+
+instance proof
+  fix a b c :: enat
+  show "(a * b) * c = a * (b * c)"
+    unfolding times_enat_def zero_enat_def
+    by (simp split: enat.split)
+  show "a * b = b * a"
+    unfolding times_enat_def zero_enat_def
+    by (simp split: enat.split)
+  show "1 * a = a"
+    unfolding times_enat_def zero_enat_def one_enat_def
+    by (simp split: enat.split)
+  show "(a + b) * c = a * c + b * c"
+    unfolding times_enat_def zero_enat_def
+    by (simp split: enat.split add: left_distrib)
+  show "0 * a = 0"
+    unfolding times_enat_def zero_enat_def
+    by (simp split: enat.split)
+  show "a * 0 = 0"
+    unfolding times_enat_def zero_enat_def
+    by (simp split: enat.split)
+  show "(0::enat) \<noteq> 1"
+    unfolding zero_enat_def one_enat_def
+    by simp
+qed
+
+end
+
+lemma mult_iSuc: "iSuc m * n = n + m * n"
+  unfolding iSuc_plus_1 by (simp add: algebra_simps)
+
+lemma mult_iSuc_right: "m * iSuc n = m + m * n"
+  unfolding iSuc_plus_1 by (simp add: algebra_simps)
+
+lemma of_nat_eq_Fin: "of_nat n = Fin n"
+  apply (induct n)
+  apply (simp add: Fin_0)
+  apply (simp add: plus_1_iSuc iSuc_Fin)
+  done
+
+instance enat :: number_semiring
+proof
+  fix n show "number_of (int n) = (of_nat n :: enat)"
+    unfolding number_of_enat_def number_of_int of_nat_id of_nat_eq_Fin ..
+qed
+
+instance enat :: semiring_char_0 proof
+  have "inj Fin" by (rule injI) simp
+  then show "inj (\<lambda>n. of_nat n :: enat)" by (simp add: of_nat_eq_Fin)
+qed
+
+lemma imult_is_0[simp]: "((m::enat) * n = 0) = (m = 0 \<or> n = 0)"
+by(auto simp add: times_enat_def zero_enat_def split: enat.split)
+
+lemma imult_is_Infty: "((a::enat) * b = \<infinity>) = (a = \<infinity> \<and> b \<noteq> 0 \<or> b = \<infinity> \<and> a \<noteq> 0)"
+by(auto simp add: times_enat_def zero_enat_def split: enat.split)
+
+
+subsection {* Subtraction *}
+
+instantiation enat :: minus
+begin
+
+definition diff_enat_def:
+"a - b = (case a of (Fin x) \<Rightarrow> (case b of (Fin y) \<Rightarrow> Fin (x - y) | \<infinity> \<Rightarrow> 0)
+          | \<infinity> \<Rightarrow> \<infinity>)"
+
+instance ..
+
+end
+
+lemma idiff_Fin_Fin[simp,code]: "Fin a - Fin b = Fin (a - b)"
+by(simp add: diff_enat_def)
+
+lemma idiff_Infty[simp,code]: "\<infinity> - n = \<infinity>"
+by(simp add: diff_enat_def)
+
+lemma idiff_Infty_right[simp,code]: "Fin a - \<infinity> = 0"
+by(simp add: diff_enat_def)
+
+lemma idiff_0[simp]: "(0::enat) - n = 0"
+by (cases n, simp_all add: zero_enat_def)
+
+lemmas idiff_Fin_0[simp] = idiff_0[unfolded zero_enat_def]
+
+lemma idiff_0_right[simp]: "(n::enat) - 0 = n"
+by (cases n) (simp_all add: zero_enat_def)
+
+lemmas idiff_Fin_0_right[simp] = idiff_0_right[unfolded zero_enat_def]
+
+lemma idiff_self[simp]: "n \<noteq> \<infinity> \<Longrightarrow> (n::enat) - n = 0"
+by(auto simp: zero_enat_def)
+
+lemma iSuc_minus_iSuc [simp]: "iSuc n - iSuc m = n - m"
+by(simp add: iSuc_def split: enat.split)
+
+lemma iSuc_minus_1 [simp]: "iSuc n - 1 = n"
+by(simp add: one_enat_def iSuc_Fin[symmetric] zero_enat_def[symmetric])
+
+(*lemmas idiff_self_eq_0_Fin = idiff_self_eq_0[unfolded zero_enat_def]*)
+
+
+subsection {* Ordering *}
+
+instantiation enat :: linordered_ab_semigroup_add
+begin
+
+definition [nitpick_simp]:
+  "m \<le> n = (case n of Fin n1 \<Rightarrow> (case m of Fin m1 \<Rightarrow> m1 \<le> n1 | \<infinity> \<Rightarrow> False)
+    | \<infinity> \<Rightarrow> True)"
+
+definition [nitpick_simp]:
+  "m < n = (case m of Fin m1 \<Rightarrow> (case n of Fin n1 \<Rightarrow> m1 < n1 | \<infinity> \<Rightarrow> True)
+    | \<infinity> \<Rightarrow> False)"
+
+lemma enat_ord_simps [simp]:
+  "Fin m \<le> Fin n \<longleftrightarrow> m \<le> n"
+  "Fin m < Fin n \<longleftrightarrow> m < n"
+  "q \<le> \<infinity>"
+  "q < \<infinity> \<longleftrightarrow> q \<noteq> \<infinity>"
+  "\<infinity> \<le> q \<longleftrightarrow> q = \<infinity>"
+  "\<infinity> < q \<longleftrightarrow> False"
+  by (simp_all add: less_eq_enat_def less_enat_def split: enat.splits)
+
+lemma enat_ord_code [code]:
+  "Fin m \<le> Fin n \<longleftrightarrow> m \<le> n"
+  "Fin m < Fin n \<longleftrightarrow> m < n"
+  "q \<le> \<infinity> \<longleftrightarrow> True"
+  "Fin m < \<infinity> \<longleftrightarrow> True"
+  "\<infinity> \<le> Fin n \<longleftrightarrow> False"
+  "\<infinity> < q \<longleftrightarrow> False"
+  by simp_all
+
+instance by default
+  (auto simp add: less_eq_enat_def less_enat_def plus_enat_def split: enat.splits)
+
+end
+
+instance enat :: ordered_comm_semiring
+proof
+  fix a b c :: enat
+  assume "a \<le> b" and "0 \<le> c"
+  thus "c * a \<le> c * b"
+    unfolding times_enat_def less_eq_enat_def zero_enat_def
+    by (simp split: enat.splits)
+qed
+
+lemma enat_ord_number [simp]:
+  "(number_of m \<Colon> enat) \<le> number_of n \<longleftrightarrow> (number_of m \<Colon> nat) \<le> number_of n"
+  "(number_of m \<Colon> enat) < number_of n \<longleftrightarrow> (number_of m \<Colon> nat) < number_of n"
+  by (simp_all add: number_of_enat_def)
+
+lemma i0_lb [simp]: "(0\<Colon>enat) \<le> n"
+  by (simp add: zero_enat_def less_eq_enat_def split: enat.splits)
+
+lemma ile0_eq [simp]: "n \<le> (0\<Colon>enat) \<longleftrightarrow> n = 0"
+by (simp add: zero_enat_def less_eq_enat_def split: enat.splits)
+
+lemma Infty_ileE [elim!]: "\<infinity> \<le> Fin m \<Longrightarrow> R"
+  by (simp add: zero_enat_def less_eq_enat_def split: enat.splits)
+
+lemma Infty_ilessE [elim!]: "\<infinity> < Fin m \<Longrightarrow> R"
+  by simp
+
+lemma not_iless0 [simp]: "\<not> n < (0\<Colon>enat)"
+  by (simp add: zero_enat_def less_enat_def split: enat.splits)
+
+lemma i0_less [simp]: "(0\<Colon>enat) < n \<longleftrightarrow> n \<noteq> 0"
+by (simp add: zero_enat_def less_enat_def split: enat.splits)
+
+lemma iSuc_ile_mono [simp]: "iSuc n \<le> iSuc m \<longleftrightarrow> n \<le> m"
+  by (simp add: iSuc_def less_eq_enat_def split: enat.splits)
+ 
+lemma iSuc_mono [simp]: "iSuc n < iSuc m \<longleftrightarrow> n < m"
+  by (simp add: iSuc_def less_enat_def split: enat.splits)
+
+lemma ile_iSuc [simp]: "n \<le> iSuc n"
+  by (simp add: iSuc_def less_eq_enat_def split: enat.splits)
+
+lemma not_iSuc_ilei0 [simp]: "\<not> iSuc n \<le> 0"
+  by (simp add: zero_enat_def iSuc_def less_eq_enat_def split: enat.splits)
+
+lemma i0_iless_iSuc [simp]: "0 < iSuc n"
+  by (simp add: zero_enat_def iSuc_def less_enat_def split: enat.splits)
+
+lemma iless_iSuc0[simp]: "(n < iSuc 0) = (n = 0)"
+by (simp add: zero_enat_def iSuc_def less_enat_def split: enat.split)
+
+lemma ileI1: "m < n \<Longrightarrow> iSuc m \<le> n"
+  by (simp add: iSuc_def less_eq_enat_def less_enat_def split: enat.splits)
+
+lemma Suc_ile_eq: "Fin (Suc m) \<le> n \<longleftrightarrow> Fin m < n"
+  by (cases n) auto
+
+lemma iless_Suc_eq [simp]: "Fin m < iSuc n \<longleftrightarrow> Fin m \<le> n"
+  by (auto simp add: iSuc_def less_enat_def split: enat.splits)
+
+lemma imult_Infty: "(0::enat) < n \<Longrightarrow> \<infinity> * n = \<infinity>"
+by (simp add: zero_enat_def less_enat_def split: enat.splits)
+
+lemma imult_Infty_right: "(0::enat) < n \<Longrightarrow> n * \<infinity> = \<infinity>"
+by (simp add: zero_enat_def less_enat_def split: enat.splits)
+
+lemma enat_0_less_mult_iff: "(0 < (m::enat) * n) = (0 < m \<and> 0 < n)"
+by (simp only: i0_less imult_is_0, simp)
+
+lemma mono_iSuc: "mono iSuc"
+by(simp add: mono_def)
+
+
+lemma min_enat_simps [simp]:
+  "min (Fin m) (Fin n) = Fin (min m n)"
+  "min q 0 = 0"
+  "min 0 q = 0"
+  "min q \<infinity> = q"
+  "min \<infinity> q = q"
+  by (auto simp add: min_def)
+
+lemma max_enat_simps [simp]:
+  "max (Fin m) (Fin n) = Fin (max m n)"
+  "max q 0 = q"
+  "max 0 q = q"
+  "max q \<infinity> = \<infinity>"
+  "max \<infinity> q = \<infinity>"
+  by (simp_all add: max_def)
+
+lemma Fin_ile: "n \<le> Fin m \<Longrightarrow> \<exists>k. n = Fin k"
+  by (cases n) simp_all
+
+lemma Fin_iless: "n < Fin m \<Longrightarrow> \<exists>k. n = Fin k"
+  by (cases n) simp_all
+
+lemma chain_incr: "\<forall>i. \<exists>j. Y i < Y j ==> \<exists>j. Fin k < Y j"
+apply (induct_tac k)
+ apply (simp (no_asm) only: Fin_0)
+ apply (fast intro: le_less_trans [OF i0_lb])
+apply (erule exE)
+apply (drule spec)
+apply (erule exE)
+apply (drule ileI1)
+apply (rule iSuc_Fin [THEN subst])
+apply (rule exI)
+apply (erule (1) le_less_trans)
+done
+
+instantiation enat :: "{bot, top}"
+begin
+
+definition bot_enat :: enat where
+  "bot_enat = 0"
+
+definition top_enat :: enat where
+  "top_enat = \<infinity>"
+
+instance proof
+qed (simp_all add: bot_enat_def top_enat_def)
+
+end
+
+lemma finite_Fin_bounded:
+  assumes le_fin: "\<And>y. y \<in> A \<Longrightarrow> y \<le> Fin n"
+  shows "finite A"
+proof (rule finite_subset)
+  show "finite (Fin ` {..n})" by blast
+
+  have "A \<subseteq> {..Fin n}" using le_fin by fastsimp
+  also have "\<dots> \<subseteq> Fin ` {..n}"
+    by (rule subsetI) (case_tac x, auto)
+  finally show "A \<subseteq> Fin ` {..n}" .
+qed
+
+
+subsection {* Well-ordering *}
+
+lemma less_FinE:
+  "[| n < Fin m; !!k. n = Fin k ==> k < m ==> P |] ==> P"
+by (induct n) auto
+
+lemma less_InftyE:
+  "[| n < Infty; !!k. n = Fin k ==> P |] ==> P"
+by (induct n) auto
+
+lemma enat_less_induct:
+  assumes prem: "!!n. \<forall>m::enat. m < n --> P m ==> P n" shows "P n"
+proof -
+  have P_Fin: "!!k. P (Fin k)"
+    apply (rule nat_less_induct)
+    apply (rule prem, clarify)
+    apply (erule less_FinE, simp)
+    done
+  show ?thesis
+  proof (induct n)
+    fix nat
+    show "P (Fin nat)" by (rule P_Fin)
+  next
+    show "P Infty"
+      apply (rule prem, clarify)
+      apply (erule less_InftyE)
+      apply (simp add: P_Fin)
+      done
+  qed
+qed
+
+instance enat :: wellorder
+proof
+  fix P and n
+  assume hyp: "(\<And>n\<Colon>enat. (\<And>m\<Colon>enat. m < n \<Longrightarrow> P m) \<Longrightarrow> P n)"
+  show "P n" by (blast intro: enat_less_induct hyp)
+qed
+
+subsection {* Complete Lattice *}
+
+instantiation enat :: complete_lattice
+begin
+
+definition inf_enat :: "enat \<Rightarrow> enat \<Rightarrow> enat" where
+  "inf_enat \<equiv> min"
+
+definition sup_enat :: "enat \<Rightarrow> enat \<Rightarrow> enat" where
+  "sup_enat \<equiv> max"
+
+definition Inf_enat :: "enat set \<Rightarrow> enat" where
+  "Inf_enat A \<equiv> if A = {} then \<infinity> else (LEAST x. x \<in> A)"
+
+definition Sup_enat :: "enat set \<Rightarrow> enat" where
+  "Sup_enat A \<equiv> if A = {} then 0
+    else if finite A then Max A
+                     else \<infinity>"
+instance proof
+  fix x :: "enat" and A :: "enat set"
+  { assume "x \<in> A" then show "Inf A \<le> x"
+      unfolding Inf_enat_def by (auto intro: Least_le) }
+  { assume "\<And>y. y \<in> A \<Longrightarrow> x \<le> y" then show "x \<le> Inf A"
+      unfolding Inf_enat_def
+      by (cases "A = {}") (auto intro: LeastI2_ex) }
+  { assume "x \<in> A" then show "x \<le> Sup A"
+      unfolding Sup_enat_def by (cases "finite A") auto }
+  { assume "\<And>y. y \<in> A \<Longrightarrow> y \<le> x" then show "Sup A \<le> x"
+      unfolding Sup_enat_def using finite_Fin_bounded by auto }
+qed (simp_all add: inf_enat_def sup_enat_def)
+end
+
+
+subsection {* Traditional theorem names *}
+
+lemmas enat_defs = zero_enat_def one_enat_def number_of_enat_def iSuc_def
+  plus_enat_def less_eq_enat_def less_enat_def
+
+end