src/HOL/Nat.thy
author haftmann
Fri Feb 05 14:33:50 2010 +0100 (2010-02-05)
changeset 35028 108662d50512
parent 34208 a7acd6c68d9b
child 35047 1b2bae06c796
permissions -rw-r--r--
more consistent naming of type classes involving orderings (and lattices) -- c.f. NEWS
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(*  Title:      HOL/Nat.thy
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    Author:     Tobias Nipkow and Lawrence C Paulson and Markus Wenzel
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Type "nat" is a linear order, and a datatype; arithmetic operators + -
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and * (for div and mod, see theory Divides).
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*)
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header {* Natural numbers *}
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theory Nat
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imports Inductive Product_Type Ring_and_Field
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uses
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  "~~/src/Tools/rat.ML"
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  "~~/src/Provers/Arith/cancel_sums.ML"
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  "Tools/arith_data.ML"
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  ("Tools/nat_arith.ML")
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  "~~/src/Provers/Arith/fast_lin_arith.ML"
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  ("Tools/lin_arith.ML")
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begin
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subsection {* Type @{text ind} *}
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typedecl ind
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axiomatization
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  Zero_Rep :: ind and
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  Suc_Rep :: "ind => ind"
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where
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  -- {* the axiom of infinity in 2 parts *}
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  Suc_Rep_inject:       "Suc_Rep x = Suc_Rep y ==> x = y" and
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  Suc_Rep_not_Zero_Rep: "Suc_Rep x \<noteq> Zero_Rep"
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subsection {* Type nat *}
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text {* Type definition *}
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inductive Nat :: "ind \<Rightarrow> bool"
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where
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    Zero_RepI: "Nat Zero_Rep"
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  | Suc_RepI: "Nat i \<Longrightarrow> Nat (Suc_Rep i)"
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global
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typedef (open Nat)
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  nat = Nat
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  by (rule exI, unfold mem_def, rule Nat.Zero_RepI)
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constdefs
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  Suc ::   "nat => nat"
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  Suc_def: "Suc == (%n. Abs_Nat (Suc_Rep (Rep_Nat n)))"
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local
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instantiation nat :: zero
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begin
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definition Zero_nat_def [code del]:
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  "0 = Abs_Nat Zero_Rep"
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instance ..
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end
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lemma Suc_not_Zero: "Suc m \<noteq> 0"
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  by (simp add: Zero_nat_def Suc_def Abs_Nat_inject [unfolded mem_def]
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    Rep_Nat [unfolded mem_def] Suc_RepI Zero_RepI Suc_Rep_not_Zero_Rep [unfolded mem_def])
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lemma Zero_not_Suc: "0 \<noteq> Suc m"
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  by (rule not_sym, rule Suc_not_Zero not_sym)
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lemma Suc_Rep_inject': "Suc_Rep x = Suc_Rep y \<longleftrightarrow> x = y"
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  by (rule iffI, rule Suc_Rep_inject) simp_all
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rep_datatype "0 \<Colon> nat" Suc
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  apply (unfold Zero_nat_def Suc_def)
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     apply (rule Rep_Nat_inverse [THEN subst]) -- {* types force good instantiation *}
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     apply (erule Rep_Nat [unfolded mem_def, THEN Nat.induct])
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     apply (iprover elim: Abs_Nat_inverse [unfolded mem_def, THEN subst])
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    apply (simp_all add: Abs_Nat_inject [unfolded mem_def] Rep_Nat [unfolded mem_def]
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      Suc_RepI Zero_RepI Suc_Rep_not_Zero_Rep [unfolded mem_def]
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      Suc_Rep_not_Zero_Rep [unfolded mem_def, symmetric]
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      Suc_Rep_inject' Rep_Nat_inject)
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  done
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lemma nat_induct [case_names 0 Suc, induct type: nat]:
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  -- {* for backward compatibility -- names of variables differ *}
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  fixes n
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  assumes "P 0"
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    and "\<And>n. P n \<Longrightarrow> P (Suc n)"
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  shows "P n"
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  using assms by (rule nat.induct)
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declare nat.exhaust [case_names 0 Suc, cases type: nat]
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lemmas nat_rec_0 = nat.recs(1)
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  and nat_rec_Suc = nat.recs(2)
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lemmas nat_case_0 = nat.cases(1)
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  and nat_case_Suc = nat.cases(2)
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text {* Injectiveness and distinctness lemmas *}
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lemma inj_Suc[simp]: "inj_on Suc N"
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  by (simp add: inj_on_def)
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lemma Suc_neq_Zero: "Suc m = 0 \<Longrightarrow> R"
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by (rule notE, rule Suc_not_Zero)
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lemma Zero_neq_Suc: "0 = Suc m \<Longrightarrow> R"
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by (rule Suc_neq_Zero, erule sym)
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lemma Suc_inject: "Suc x = Suc y \<Longrightarrow> x = y"
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by (rule inj_Suc [THEN injD])
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lemma n_not_Suc_n: "n \<noteq> Suc n"
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by (induct n) simp_all
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lemma Suc_n_not_n: "Suc n \<noteq> n"
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by (rule not_sym, rule n_not_Suc_n)
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text {* A special form of induction for reasoning
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  about @{term "m < n"} and @{term "m - n"} *}
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lemma diff_induct: "(!!x. P x 0) ==> (!!y. P 0 (Suc y)) ==>
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    (!!x y. P x y ==> P (Suc x) (Suc y)) ==> P m n"
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  apply (rule_tac x = m in spec)
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  apply (induct n)
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  prefer 2
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  apply (rule allI)
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  apply (induct_tac x, iprover+)
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  done
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subsection {* Arithmetic operators *}
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instantiation nat :: "{minus, comm_monoid_add}"
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begin
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primrec plus_nat
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where
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  add_0:      "0 + n = (n\<Colon>nat)"
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  | add_Suc:  "Suc m + n = Suc (m + n)"
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lemma add_0_right [simp]: "m + 0 = (m::nat)"
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  by (induct m) simp_all
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lemma add_Suc_right [simp]: "m + Suc n = Suc (m + n)"
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  by (induct m) simp_all
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declare add_0 [code]
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lemma add_Suc_shift [code]: "Suc m + n = m + Suc n"
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  by simp
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primrec minus_nat
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where
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  diff_0:     "m - 0 = (m\<Colon>nat)"
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  | diff_Suc: "m - Suc n = (case m - n of 0 => 0 | Suc k => k)"
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declare diff_Suc [simp del]
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declare diff_0 [code]
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lemma diff_0_eq_0 [simp, code]: "0 - n = (0::nat)"
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  by (induct n) (simp_all add: diff_Suc)
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lemma diff_Suc_Suc [simp, code]: "Suc m - Suc n = m - n"
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  by (induct n) (simp_all add: diff_Suc)
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instance proof
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  fix n m q :: nat
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  show "(n + m) + q = n + (m + q)" by (induct n) simp_all
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  show "n + m = m + n" by (induct n) simp_all
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  show "0 + n = n" by simp
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qed
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end
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instantiation nat :: comm_semiring_1_cancel
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begin
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definition
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  One_nat_def [simp]: "1 = Suc 0"
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primrec times_nat
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where
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  mult_0:     "0 * n = (0\<Colon>nat)"
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  | mult_Suc: "Suc m * n = n + (m * n)"
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lemma mult_0_right [simp]: "(m::nat) * 0 = 0"
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  by (induct m) simp_all
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lemma mult_Suc_right [simp]: "m * Suc n = m + (m * n)"
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  by (induct m) (simp_all add: add_left_commute)
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lemma add_mult_distrib: "(m + n) * k = (m * k) + ((n * k)::nat)"
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  by (induct m) (simp_all add: add_assoc)
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instance proof
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  fix n m q :: nat
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  show "0 \<noteq> (1::nat)" unfolding One_nat_def by simp
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  show "1 * n = n" unfolding One_nat_def by simp
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  show "n * m = m * n" by (induct n) simp_all
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  show "(n * m) * q = n * (m * q)" by (induct n) (simp_all add: add_mult_distrib)
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  show "(n + m) * q = n * q + m * q" by (rule add_mult_distrib)
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  assume "n + m = n + q" thus "m = q" by (induct n) simp_all
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qed
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end
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subsubsection {* Addition *}
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lemma nat_add_assoc: "(m + n) + k = m + ((n + k)::nat)"
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  by (rule add_assoc)
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lemma nat_add_commute: "m + n = n + (m::nat)"
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  by (rule add_commute)
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lemma nat_add_left_commute: "x + (y + z) = y + ((x + z)::nat)"
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  by (rule add_left_commute)
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lemma nat_add_left_cancel [simp]: "(k + m = k + n) = (m = (n::nat))"
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  by (rule add_left_cancel)
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lemma nat_add_right_cancel [simp]: "(m + k = n + k) = (m=(n::nat))"
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  by (rule add_right_cancel)
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text {* Reasoning about @{text "m + 0 = 0"}, etc. *}
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lemma add_is_0 [iff]:
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  fixes m n :: nat
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  shows "(m + n = 0) = (m = 0 & n = 0)"
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  by (cases m) simp_all
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lemma add_is_1:
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  "(m+n= Suc 0) = (m= Suc 0 & n=0 | m=0 & n= Suc 0)"
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  by (cases m) simp_all
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lemma one_is_add:
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  "(Suc 0 = m + n) = (m = Suc 0 & n = 0 | m = 0 & n = Suc 0)"
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  by (rule trans, rule eq_commute, rule add_is_1)
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lemma add_eq_self_zero:
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  fixes m n :: nat
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  shows "m + n = m \<Longrightarrow> n = 0"
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  by (induct m) simp_all
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lemma inj_on_add_nat[simp]: "inj_on (%n::nat. n+k) N"
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  apply (induct k)
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   apply simp
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  apply(drule comp_inj_on[OF _ inj_Suc])
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  apply (simp add:o_def)
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  done
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subsubsection {* Difference *}
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lemma diff_self_eq_0 [simp]: "(m\<Colon>nat) - m = 0"
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  by (induct m) simp_all
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lemma diff_diff_left: "(i::nat) - j - k = i - (j + k)"
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  by (induct i j rule: diff_induct) simp_all
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lemma Suc_diff_diff [simp]: "(Suc m - n) - Suc k = m - n - k"
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  by (simp add: diff_diff_left)
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lemma diff_commute: "(i::nat) - j - k = i - k - j"
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  by (simp add: diff_diff_left add_commute)
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lemma diff_add_inverse: "(n + m) - n = (m::nat)"
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  by (induct n) simp_all
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lemma diff_add_inverse2: "(m + n) - n = (m::nat)"
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  by (simp add: diff_add_inverse add_commute [of m n])
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lemma diff_cancel: "(k + m) - (k + n) = m - (n::nat)"
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  by (induct k) simp_all
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lemma diff_cancel2: "(m + k) - (n + k) = m - (n::nat)"
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  by (simp add: diff_cancel add_commute)
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lemma diff_add_0: "n - (n + m) = (0::nat)"
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  by (induct n) simp_all
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lemma diff_Suc_1 [simp]: "Suc n - 1 = n"
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  unfolding One_nat_def by simp
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text {* Difference distributes over multiplication *}
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lemma diff_mult_distrib: "((m::nat) - n) * k = (m * k) - (n * k)"
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by (induct m n rule: diff_induct) (simp_all add: diff_cancel)
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lemma diff_mult_distrib2: "k * ((m::nat) - n) = (k * m) - (k * n)"
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by (simp add: diff_mult_distrib mult_commute [of k])
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  -- {* NOT added as rewrites, since sometimes they are used from right-to-left *}
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subsubsection {* Multiplication *}
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lemma nat_mult_assoc: "(m * n) * k = m * ((n * k)::nat)"
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  by (rule mult_assoc)
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lemma nat_mult_commute: "m * n = n * (m::nat)"
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  by (rule mult_commute)
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lemma add_mult_distrib2: "k * (m + n) = (k * m) + ((k * n)::nat)"
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  by (rule right_distrib)
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lemma mult_is_0 [simp]: "((m::nat) * n = 0) = (m=0 | n=0)"
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  by (induct m) auto
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lemmas nat_distrib =
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  add_mult_distrib add_mult_distrib2 diff_mult_distrib diff_mult_distrib2
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lemma mult_eq_1_iff [simp]: "(m * n = Suc 0) = (m = Suc 0 & n = Suc 0)"
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  apply (induct m)
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   apply simp
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  apply (induct n)
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   apply auto
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  done
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lemma one_eq_mult_iff [simp,noatp]: "(Suc 0 = m * n) = (m = Suc 0 & n = Suc 0)"
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  apply (rule trans)
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  apply (rule_tac [2] mult_eq_1_iff, fastsimp)
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  done
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lemma nat_mult_eq_1_iff [simp]: "m * n = (1::nat) \<longleftrightarrow> m = 1 \<and> n = 1"
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  unfolding One_nat_def by (rule mult_eq_1_iff)
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lemma nat_1_eq_mult_iff [simp]: "(1::nat) = m * n \<longleftrightarrow> m = 1 \<and> n = 1"
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  unfolding One_nat_def by (rule one_eq_mult_iff)
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lemma mult_cancel1 [simp]: "(k * m = k * n) = (m = n | (k = (0::nat)))"
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proof -
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  have "k \<noteq> 0 \<Longrightarrow> k * m = k * n \<Longrightarrow> m = n"
haftmann@26072
   336
  proof (induct n arbitrary: m)
haftmann@26072
   337
    case 0 then show "m = 0" by simp
haftmann@26072
   338
  next
haftmann@26072
   339
    case (Suc n) then show "m = Suc n"
haftmann@26072
   340
      by (cases m) (simp_all add: eq_commute [of "0"])
haftmann@26072
   341
  qed
haftmann@26072
   342
  then show ?thesis by auto
haftmann@26072
   343
qed
haftmann@26072
   344
haftmann@26072
   345
lemma mult_cancel2 [simp]: "(m * k = n * k) = (m = n | (k = (0::nat)))"
haftmann@26072
   346
  by (simp add: mult_commute)
haftmann@26072
   347
haftmann@26072
   348
lemma Suc_mult_cancel1: "(Suc k * m = Suc k * n) = (m = n)"
haftmann@26072
   349
  by (subst mult_cancel1) simp
haftmann@26072
   350
haftmann@24995
   351
haftmann@24995
   352
subsection {* Orders on @{typ nat} *}
haftmann@24995
   353
haftmann@26072
   354
subsubsection {* Operation definition *}
haftmann@24995
   355
haftmann@26072
   356
instantiation nat :: linorder
haftmann@25510
   357
begin
haftmann@25510
   358
haftmann@26072
   359
primrec less_eq_nat where
haftmann@26072
   360
  "(0\<Colon>nat) \<le> n \<longleftrightarrow> True"
haftmann@26072
   361
  | "Suc m \<le> n \<longleftrightarrow> (case n of 0 \<Rightarrow> False | Suc n \<Rightarrow> m \<le> n)"
haftmann@26072
   362
haftmann@28514
   363
declare less_eq_nat.simps [simp del]
haftmann@26072
   364
lemma [code]: "(0\<Colon>nat) \<le> n \<longleftrightarrow> True" by (simp add: less_eq_nat.simps)
haftmann@26072
   365
lemma le0 [iff]: "0 \<le> (n\<Colon>nat)" by (simp add: less_eq_nat.simps)
haftmann@26072
   366
haftmann@26072
   367
definition less_nat where
haftmann@28514
   368
  less_eq_Suc_le: "n < m \<longleftrightarrow> Suc n \<le> m"
haftmann@26072
   369
haftmann@26072
   370
lemma Suc_le_mono [iff]: "Suc n \<le> Suc m \<longleftrightarrow> n \<le> m"
haftmann@26072
   371
  by (simp add: less_eq_nat.simps(2))
haftmann@26072
   372
haftmann@26072
   373
lemma Suc_le_eq [code]: "Suc m \<le> n \<longleftrightarrow> m < n"
haftmann@26072
   374
  unfolding less_eq_Suc_le ..
haftmann@26072
   375
haftmann@26072
   376
lemma le_0_eq [iff]: "(n\<Colon>nat) \<le> 0 \<longleftrightarrow> n = 0"
haftmann@26072
   377
  by (induct n) (simp_all add: less_eq_nat.simps(2))
haftmann@26072
   378
haftmann@26072
   379
lemma not_less0 [iff]: "\<not> n < (0\<Colon>nat)"
haftmann@26072
   380
  by (simp add: less_eq_Suc_le)
haftmann@26072
   381
haftmann@26072
   382
lemma less_nat_zero_code [code]: "n < (0\<Colon>nat) \<longleftrightarrow> False"
haftmann@26072
   383
  by simp
haftmann@26072
   384
haftmann@26072
   385
lemma Suc_less_eq [iff]: "Suc m < Suc n \<longleftrightarrow> m < n"
haftmann@26072
   386
  by (simp add: less_eq_Suc_le)
haftmann@26072
   387
haftmann@26072
   388
lemma less_Suc_eq_le [code]: "m < Suc n \<longleftrightarrow> m \<le> n"
haftmann@26072
   389
  by (simp add: less_eq_Suc_le)
haftmann@26072
   390
haftmann@26072
   391
lemma le_SucI: "m \<le> n \<Longrightarrow> m \<le> Suc n"
haftmann@26072
   392
  by (induct m arbitrary: n)
haftmann@26072
   393
    (simp_all add: less_eq_nat.simps(2) split: nat.splits)
haftmann@26072
   394
haftmann@26072
   395
lemma Suc_leD: "Suc m \<le> n \<Longrightarrow> m \<le> n"
haftmann@26072
   396
  by (cases n) (auto intro: le_SucI)
haftmann@26072
   397
haftmann@26072
   398
lemma less_SucI: "m < n \<Longrightarrow> m < Suc n"
haftmann@26072
   399
  by (simp add: less_eq_Suc_le) (erule Suc_leD)
haftmann@24995
   400
haftmann@26072
   401
lemma Suc_lessD: "Suc m < n \<Longrightarrow> m < n"
haftmann@26072
   402
  by (simp add: less_eq_Suc_le) (erule Suc_leD)
haftmann@25510
   403
wenzelm@26315
   404
instance
wenzelm@26315
   405
proof
haftmann@26072
   406
  fix n m :: nat
haftmann@27679
   407
  show "n < m \<longleftrightarrow> n \<le> m \<and> \<not> m \<le> n" 
haftmann@26072
   408
  proof (induct n arbitrary: m)
haftmann@27679
   409
    case 0 then show ?case by (cases m) (simp_all add: less_eq_Suc_le)
haftmann@26072
   410
  next
haftmann@27679
   411
    case (Suc n) then show ?case by (cases m) (simp_all add: less_eq_Suc_le)
haftmann@26072
   412
  qed
haftmann@26072
   413
next
haftmann@26072
   414
  fix n :: nat show "n \<le> n" by (induct n) simp_all
haftmann@26072
   415
next
haftmann@26072
   416
  fix n m :: nat assume "n \<le> m" and "m \<le> n"
haftmann@26072
   417
  then show "n = m"
haftmann@26072
   418
    by (induct n arbitrary: m)
haftmann@26072
   419
      (simp_all add: less_eq_nat.simps(2) split: nat.splits)
haftmann@26072
   420
next
haftmann@26072
   421
  fix n m q :: nat assume "n \<le> m" and "m \<le> q"
haftmann@26072
   422
  then show "n \<le> q"
haftmann@26072
   423
  proof (induct n arbitrary: m q)
haftmann@26072
   424
    case 0 show ?case by simp
haftmann@26072
   425
  next
haftmann@26072
   426
    case (Suc n) then show ?case
haftmann@26072
   427
      by (simp_all (no_asm_use) add: less_eq_nat.simps(2) split: nat.splits, clarify,
haftmann@26072
   428
        simp_all (no_asm_use) add: less_eq_nat.simps(2) split: nat.splits, clarify,
haftmann@26072
   429
        simp_all (no_asm_use) add: less_eq_nat.simps(2) split: nat.splits)
haftmann@26072
   430
  qed
haftmann@26072
   431
next
haftmann@26072
   432
  fix n m :: nat show "n \<le> m \<or> m \<le> n"
haftmann@26072
   433
    by (induct n arbitrary: m)
haftmann@26072
   434
      (simp_all add: less_eq_nat.simps(2) split: nat.splits)
haftmann@26072
   435
qed
haftmann@25510
   436
haftmann@25510
   437
end
berghofe@13449
   438
haftmann@29652
   439
instantiation nat :: bot
haftmann@29652
   440
begin
haftmann@29652
   441
haftmann@29652
   442
definition bot_nat :: nat where
haftmann@29652
   443
  "bot_nat = 0"
haftmann@29652
   444
haftmann@29652
   445
instance proof
haftmann@29652
   446
qed (simp add: bot_nat_def)
haftmann@29652
   447
haftmann@29652
   448
end
haftmann@29652
   449
haftmann@26072
   450
subsubsection {* Introduction properties *}
berghofe@13449
   451
haftmann@26072
   452
lemma lessI [iff]: "n < Suc n"
haftmann@26072
   453
  by (simp add: less_Suc_eq_le)
berghofe@13449
   454
haftmann@26072
   455
lemma zero_less_Suc [iff]: "0 < Suc n"
haftmann@26072
   456
  by (simp add: less_Suc_eq_le)
berghofe@13449
   457
berghofe@13449
   458
berghofe@13449
   459
subsubsection {* Elimination properties *}
berghofe@13449
   460
berghofe@13449
   461
lemma less_not_refl: "~ n < (n::nat)"
haftmann@26072
   462
  by (rule order_less_irrefl)
berghofe@13449
   463
wenzelm@26335
   464
lemma less_not_refl2: "n < m ==> m \<noteq> (n::nat)"
wenzelm@26335
   465
  by (rule not_sym) (rule less_imp_neq) 
berghofe@13449
   466
paulson@14267
   467
lemma less_not_refl3: "(s::nat) < t ==> s \<noteq> t"
haftmann@26072
   468
  by (rule less_imp_neq)
berghofe@13449
   469
wenzelm@26335
   470
lemma less_irrefl_nat: "(n::nat) < n ==> R"
wenzelm@26335
   471
  by (rule notE, rule less_not_refl)
berghofe@13449
   472
berghofe@13449
   473
lemma less_zeroE: "(n::nat) < 0 ==> R"
haftmann@26072
   474
  by (rule notE) (rule not_less0)
berghofe@13449
   475
berghofe@13449
   476
lemma less_Suc_eq: "(m < Suc n) = (m < n | m = n)"
haftmann@26072
   477
  unfolding less_Suc_eq_le le_less ..
berghofe@13449
   478
huffman@30079
   479
lemma less_Suc0 [iff]: "(n < Suc 0) = (n = 0)"
haftmann@26072
   480
  by (simp add: less_Suc_eq)
berghofe@13449
   481
huffman@30079
   482
lemma less_one [iff, noatp]: "(n < (1::nat)) = (n = 0)"
huffman@30079
   483
  unfolding One_nat_def by (rule less_Suc0)
berghofe@13449
   484
berghofe@13449
   485
lemma Suc_mono: "m < n ==> Suc m < Suc n"
haftmann@26072
   486
  by simp
berghofe@13449
   487
nipkow@14302
   488
text {* "Less than" is antisymmetric, sort of *}
nipkow@14302
   489
lemma less_antisym: "\<lbrakk> \<not> n < m; n < Suc m \<rbrakk> \<Longrightarrow> m = n"
haftmann@26072
   490
  unfolding not_less less_Suc_eq_le by (rule antisym)
nipkow@14302
   491
paulson@14267
   492
lemma nat_neq_iff: "((m::nat) \<noteq> n) = (m < n | n < m)"
haftmann@26072
   493
  by (rule linorder_neq_iff)
berghofe@13449
   494
berghofe@13449
   495
lemma nat_less_cases: assumes major: "(m::nat) < n ==> P n m"
berghofe@13449
   496
  and eqCase: "m = n ==> P n m" and lessCase: "n<m ==> P n m"
berghofe@13449
   497
  shows "P n m"
berghofe@13449
   498
  apply (rule less_linear [THEN disjE])
berghofe@13449
   499
  apply (erule_tac [2] disjE)
berghofe@13449
   500
  apply (erule lessCase)
berghofe@13449
   501
  apply (erule sym [THEN eqCase])
berghofe@13449
   502
  apply (erule major)
berghofe@13449
   503
  done
berghofe@13449
   504
berghofe@13449
   505
berghofe@13449
   506
subsubsection {* Inductive (?) properties *}
berghofe@13449
   507
paulson@14267
   508
lemma Suc_lessI: "m < n ==> Suc m \<noteq> n ==> Suc m < n"
haftmann@26072
   509
  unfolding less_eq_Suc_le [of m] le_less by simp 
berghofe@13449
   510
haftmann@26072
   511
lemma lessE:
haftmann@26072
   512
  assumes major: "i < k"
haftmann@26072
   513
  and p1: "k = Suc i ==> P" and p2: "!!j. i < j ==> k = Suc j ==> P"
haftmann@26072
   514
  shows P
haftmann@26072
   515
proof -
haftmann@26072
   516
  from major have "\<exists>j. i \<le> j \<and> k = Suc j"
haftmann@26072
   517
    unfolding less_eq_Suc_le by (induct k) simp_all
haftmann@26072
   518
  then have "(\<exists>j. i < j \<and> k = Suc j) \<or> k = Suc i"
haftmann@26072
   519
    by (clarsimp simp add: less_le)
haftmann@26072
   520
  with p1 p2 show P by auto
haftmann@26072
   521
qed
haftmann@26072
   522
haftmann@26072
   523
lemma less_SucE: assumes major: "m < Suc n"
haftmann@26072
   524
  and less: "m < n ==> P" and eq: "m = n ==> P" shows P
haftmann@26072
   525
  apply (rule major [THEN lessE])
haftmann@26072
   526
  apply (rule eq, blast)
haftmann@26072
   527
  apply (rule less, blast)
berghofe@13449
   528
  done
berghofe@13449
   529
berghofe@13449
   530
lemma Suc_lessE: assumes major: "Suc i < k"
berghofe@13449
   531
  and minor: "!!j. i < j ==> k = Suc j ==> P" shows P
berghofe@13449
   532
  apply (rule major [THEN lessE])
berghofe@13449
   533
  apply (erule lessI [THEN minor])
paulson@14208
   534
  apply (erule Suc_lessD [THEN minor], assumption)
berghofe@13449
   535
  done
berghofe@13449
   536
berghofe@13449
   537
lemma Suc_less_SucD: "Suc m < Suc n ==> m < n"
haftmann@26072
   538
  by simp
berghofe@13449
   539
berghofe@13449
   540
lemma less_trans_Suc:
berghofe@13449
   541
  assumes le: "i < j" shows "j < k ==> Suc i < k"
paulson@14208
   542
  apply (induct k, simp_all)
berghofe@13449
   543
  apply (insert le)
berghofe@13449
   544
  apply (simp add: less_Suc_eq)
berghofe@13449
   545
  apply (blast dest: Suc_lessD)
berghofe@13449
   546
  done
berghofe@13449
   547
berghofe@13449
   548
text {* Can be used with @{text less_Suc_eq} to get @{term "n = m | n < m"} *}
haftmann@26072
   549
lemma not_less_eq: "\<not> m < n \<longleftrightarrow> n < Suc m"
haftmann@26072
   550
  unfolding not_less less_Suc_eq_le ..
berghofe@13449
   551
haftmann@26072
   552
lemma not_less_eq_eq: "\<not> m \<le> n \<longleftrightarrow> Suc n \<le> m"
haftmann@26072
   553
  unfolding not_le Suc_le_eq ..
wenzelm@21243
   554
haftmann@24995
   555
text {* Properties of "less than or equal" *}
berghofe@13449
   556
paulson@14267
   557
lemma le_imp_less_Suc: "m \<le> n ==> m < Suc n"
haftmann@26072
   558
  unfolding less_Suc_eq_le .
berghofe@13449
   559
paulson@14267
   560
lemma Suc_n_not_le_n: "~ Suc n \<le> n"
haftmann@26072
   561
  unfolding not_le less_Suc_eq_le ..
berghofe@13449
   562
paulson@14267
   563
lemma le_Suc_eq: "(m \<le> Suc n) = (m \<le> n | m = Suc n)"
haftmann@26072
   564
  by (simp add: less_Suc_eq_le [symmetric] less_Suc_eq)
berghofe@13449
   565
paulson@14267
   566
lemma le_SucE: "m \<le> Suc n ==> (m \<le> n ==> R) ==> (m = Suc n ==> R) ==> R"
haftmann@26072
   567
  by (drule le_Suc_eq [THEN iffD1], iprover+)
berghofe@13449
   568
paulson@14267
   569
lemma Suc_leI: "m < n ==> Suc(m) \<le> n"
haftmann@26072
   570
  unfolding Suc_le_eq .
berghofe@13449
   571
berghofe@13449
   572
text {* Stronger version of @{text Suc_leD} *}
paulson@14267
   573
lemma Suc_le_lessD: "Suc m \<le> n ==> m < n"
haftmann@26072
   574
  unfolding Suc_le_eq .
berghofe@13449
   575
wenzelm@26315
   576
lemma less_imp_le_nat: "m < n ==> m \<le> (n::nat)"
haftmann@26072
   577
  unfolding less_eq_Suc_le by (rule Suc_leD)
berghofe@13449
   578
paulson@14267
   579
text {* For instance, @{text "(Suc m < Suc n) = (Suc m \<le> n) = (m < n)"} *}
wenzelm@26315
   580
lemmas le_simps = less_imp_le_nat less_Suc_eq_le Suc_le_eq
berghofe@13449
   581
berghofe@13449
   582
paulson@14267
   583
text {* Equivalence of @{term "m \<le> n"} and @{term "m < n | m = n"} *}
berghofe@13449
   584
paulson@14267
   585
lemma less_or_eq_imp_le: "m < n | m = n ==> m \<le> (n::nat)"
haftmann@26072
   586
  unfolding le_less .
berghofe@13449
   587
paulson@14267
   588
lemma le_eq_less_or_eq: "(m \<le> (n::nat)) = (m < n | m=n)"
haftmann@26072
   589
  by (rule le_less)
berghofe@13449
   590
wenzelm@22718
   591
text {* Useful with @{text blast}. *}
paulson@14267
   592
lemma eq_imp_le: "(m::nat) = n ==> m \<le> n"
haftmann@26072
   593
  by auto
berghofe@13449
   594
paulson@14267
   595
lemma le_refl: "n \<le> (n::nat)"
haftmann@26072
   596
  by simp
berghofe@13449
   597
paulson@14267
   598
lemma le_trans: "[| i \<le> j; j \<le> k |] ==> i \<le> (k::nat)"
haftmann@26072
   599
  by (rule order_trans)
berghofe@13449
   600
nipkow@33657
   601
lemma le_antisym: "[| m \<le> n; n \<le> m |] ==> m = (n::nat)"
haftmann@26072
   602
  by (rule antisym)
berghofe@13449
   603
paulson@14267
   604
lemma nat_less_le: "((m::nat) < n) = (m \<le> n & m \<noteq> n)"
haftmann@26072
   605
  by (rule less_le)
berghofe@13449
   606
paulson@14267
   607
lemma le_neq_implies_less: "(m::nat) \<le> n ==> m \<noteq> n ==> m < n"
haftmann@26072
   608
  unfolding less_le ..
berghofe@13449
   609
haftmann@26072
   610
lemma nat_le_linear: "(m::nat) \<le> n | n \<le> m"
haftmann@26072
   611
  by (rule linear)
paulson@14341
   612
wenzelm@22718
   613
lemmas linorder_neqE_nat = linorder_neqE [where 'a = nat]
nipkow@15921
   614
haftmann@26072
   615
lemma le_less_Suc_eq: "m \<le> n ==> (n < Suc m) = (n = m)"
haftmann@26072
   616
  unfolding less_Suc_eq_le by auto
berghofe@13449
   617
haftmann@26072
   618
lemma not_less_less_Suc_eq: "~ n < m ==> (n < Suc m) = (n = m)"
haftmann@26072
   619
  unfolding not_less by (rule le_less_Suc_eq)
berghofe@13449
   620
berghofe@13449
   621
lemmas not_less_simps = not_less_less_Suc_eq le_less_Suc_eq
berghofe@13449
   622
wenzelm@22718
   623
text {* These two rules ease the use of primitive recursion.
paulson@14341
   624
NOTE USE OF @{text "=="} *}
berghofe@13449
   625
lemma def_nat_rec_0: "(!!n. f n == nat_rec c h n) ==> f 0 = c"
nipkow@25162
   626
by simp
berghofe@13449
   627
berghofe@13449
   628
lemma def_nat_rec_Suc: "(!!n. f n == nat_rec c h n) ==> f (Suc n) = h n (f n)"
nipkow@25162
   629
by simp
berghofe@13449
   630
paulson@14267
   631
lemma not0_implies_Suc: "n \<noteq> 0 ==> \<exists>m. n = Suc m"
nipkow@25162
   632
by (cases n) simp_all
nipkow@25162
   633
nipkow@25162
   634
lemma gr0_implies_Suc: "n > 0 ==> \<exists>m. n = Suc m"
nipkow@25162
   635
by (cases n) simp_all
berghofe@13449
   636
wenzelm@22718
   637
lemma gr_implies_not0: fixes n :: nat shows "m<n ==> n \<noteq> 0"
nipkow@25162
   638
by (cases n) simp_all
berghofe@13449
   639
nipkow@25162
   640
lemma neq0_conv[iff]: fixes n :: nat shows "(n \<noteq> 0) = (0 < n)"
nipkow@25162
   641
by (cases n) simp_all
nipkow@25140
   642
berghofe@13449
   643
text {* This theorem is useful with @{text blast} *}
berghofe@13449
   644
lemma gr0I: "((n::nat) = 0 ==> False) ==> 0 < n"
nipkow@25162
   645
by (rule neq0_conv[THEN iffD1], iprover)
berghofe@13449
   646
paulson@14267
   647
lemma gr0_conv_Suc: "(0 < n) = (\<exists>m. n = Suc m)"
nipkow@25162
   648
by (fast intro: not0_implies_Suc)
berghofe@13449
   649
paulson@24286
   650
lemma not_gr0 [iff,noatp]: "!!n::nat. (~ (0 < n)) = (n = 0)"
nipkow@25134
   651
using neq0_conv by blast
berghofe@13449
   652
paulson@14267
   653
lemma Suc_le_D: "(Suc n \<le> m') ==> (? m. m' = Suc m)"
nipkow@25162
   654
by (induct m') simp_all
berghofe@13449
   655
berghofe@13449
   656
text {* Useful in certain inductive arguments *}
paulson@14267
   657
lemma less_Suc_eq_0_disj: "(m < Suc n) = (m = 0 | (\<exists>j. m = Suc j & j < n))"
nipkow@25162
   658
by (cases m) simp_all
berghofe@13449
   659
berghofe@13449
   660
haftmann@26072
   661
subsubsection {* @{term min} and @{term max} *}
berghofe@13449
   662
haftmann@25076
   663
lemma mono_Suc: "mono Suc"
nipkow@25162
   664
by (rule monoI) simp
haftmann@25076
   665
berghofe@13449
   666
lemma min_0L [simp]: "min 0 n = (0::nat)"
nipkow@25162
   667
by (rule min_leastL) simp
berghofe@13449
   668
berghofe@13449
   669
lemma min_0R [simp]: "min n 0 = (0::nat)"
nipkow@25162
   670
by (rule min_leastR) simp
berghofe@13449
   671
berghofe@13449
   672
lemma min_Suc_Suc [simp]: "min (Suc m) (Suc n) = Suc (min m n)"
nipkow@25162
   673
by (simp add: mono_Suc min_of_mono)
berghofe@13449
   674
paulson@22191
   675
lemma min_Suc1:
paulson@22191
   676
   "min (Suc n) m = (case m of 0 => 0 | Suc m' => Suc(min n m'))"
nipkow@25162
   677
by (simp split: nat.split)
paulson@22191
   678
paulson@22191
   679
lemma min_Suc2:
paulson@22191
   680
   "min m (Suc n) = (case m of 0 => 0 | Suc m' => Suc(min m' n))"
nipkow@25162
   681
by (simp split: nat.split)
paulson@22191
   682
berghofe@13449
   683
lemma max_0L [simp]: "max 0 n = (n::nat)"
nipkow@25162
   684
by (rule max_leastL) simp
berghofe@13449
   685
berghofe@13449
   686
lemma max_0R [simp]: "max n 0 = (n::nat)"
nipkow@25162
   687
by (rule max_leastR) simp
berghofe@13449
   688
berghofe@13449
   689
lemma max_Suc_Suc [simp]: "max (Suc m) (Suc n) = Suc(max m n)"
nipkow@25162
   690
by (simp add: mono_Suc max_of_mono)
berghofe@13449
   691
paulson@22191
   692
lemma max_Suc1:
paulson@22191
   693
   "max (Suc n) m = (case m of 0 => Suc n | Suc m' => Suc(max n m'))"
nipkow@25162
   694
by (simp split: nat.split)
paulson@22191
   695
paulson@22191
   696
lemma max_Suc2:
paulson@22191
   697
   "max m (Suc n) = (case m of 0 => Suc n | Suc m' => Suc(max m' n))"
nipkow@25162
   698
by (simp split: nat.split)
paulson@22191
   699
berghofe@13449
   700
haftmann@26072
   701
subsubsection {* Monotonicity of Addition *}
berghofe@13449
   702
haftmann@26072
   703
lemma Suc_pred [simp]: "n>0 ==> Suc (n - Suc 0) = n"
haftmann@26072
   704
by (simp add: diff_Suc split: nat.split)
berghofe@13449
   705
huffman@30128
   706
lemma Suc_diff_1 [simp]: "0 < n ==> Suc (n - 1) = n"
huffman@30128
   707
unfolding One_nat_def by (rule Suc_pred)
huffman@30128
   708
paulson@14331
   709
lemma nat_add_left_cancel_le [simp]: "(k + m \<le> k + n) = (m\<le>(n::nat))"
nipkow@25162
   710
by (induct k) simp_all
berghofe@13449
   711
paulson@14331
   712
lemma nat_add_left_cancel_less [simp]: "(k + m < k + n) = (m<(n::nat))"
nipkow@25162
   713
by (induct k) simp_all
berghofe@13449
   714
nipkow@25162
   715
lemma add_gr_0 [iff]: "!!m::nat. (m + n > 0) = (m>0 | n>0)"
nipkow@25162
   716
by(auto dest:gr0_implies_Suc)
berghofe@13449
   717
paulson@14341
   718
text {* strict, in 1st argument *}
paulson@14341
   719
lemma add_less_mono1: "i < j ==> i + k < j + (k::nat)"
nipkow@25162
   720
by (induct k) simp_all
paulson@14341
   721
paulson@14341
   722
text {* strict, in both arguments *}
paulson@14341
   723
lemma add_less_mono: "[|i < j; k < l|] ==> i + k < j + (l::nat)"
paulson@14341
   724
  apply (rule add_less_mono1 [THEN less_trans], assumption+)
paulson@15251
   725
  apply (induct j, simp_all)
paulson@14341
   726
  done
paulson@14341
   727
paulson@14341
   728
text {* Deleted @{text less_natE}; use @{text "less_imp_Suc_add RS exE"} *}
paulson@14341
   729
lemma less_imp_Suc_add: "m < n ==> (\<exists>k. n = Suc (m + k))"
paulson@14341
   730
  apply (induct n)
paulson@14341
   731
  apply (simp_all add: order_le_less)
wenzelm@22718
   732
  apply (blast elim!: less_SucE
paulson@14341
   733
               intro!: add_0_right [symmetric] add_Suc_right [symmetric])
paulson@14341
   734
  done
paulson@14341
   735
paulson@14341
   736
text {* strict, in 1st argument; proof is by induction on @{text "k > 0"} *}
nipkow@25134
   737
lemma mult_less_mono2: "(i::nat) < j ==> 0<k ==> k * i < k * j"
nipkow@25134
   738
apply(auto simp: gr0_conv_Suc)
nipkow@25134
   739
apply (induct_tac m)
nipkow@25134
   740
apply (simp_all add: add_less_mono)
nipkow@25134
   741
done
paulson@14341
   742
nipkow@14740
   743
text{*The naturals form an ordered @{text comm_semiring_1_cancel}*}
haftmann@35028
   744
instance nat :: linordered_semidom
paulson@14341
   745
proof
paulson@14341
   746
  fix i j k :: nat
paulson@14348
   747
  show "0 < (1::nat)" by simp
paulson@14267
   748
  show "i \<le> j ==> k + i \<le> k + j" by simp
paulson@14267
   749
  show "i < j ==> 0 < k ==> k * i < k * j" by (simp add: mult_less_mono2)
paulson@14267
   750
qed
paulson@14267
   751
nipkow@30056
   752
instance nat :: no_zero_divisors
nipkow@30056
   753
proof
nipkow@30056
   754
  fix a::nat and b::nat show "a ~= 0 \<Longrightarrow> b ~= 0 \<Longrightarrow> a * b ~= 0" by auto
nipkow@30056
   755
qed
nipkow@30056
   756
paulson@14267
   757
lemma nat_mult_1: "(1::nat) * n = n"
nipkow@25162
   758
by simp
paulson@14267
   759
paulson@14267
   760
lemma nat_mult_1_right: "n * (1::nat) = n"
nipkow@25162
   761
by simp
paulson@14267
   762
paulson@14267
   763
krauss@26748
   764
subsubsection {* Additional theorems about @{term "op \<le>"} *}
krauss@26748
   765
krauss@26748
   766
text {* Complete induction, aka course-of-values induction *}
krauss@26748
   767
haftmann@27823
   768
instance nat :: wellorder proof
haftmann@27823
   769
  fix P and n :: nat
haftmann@27823
   770
  assume step: "\<And>n::nat. (\<And>m. m < n \<Longrightarrow> P m) \<Longrightarrow> P n"
haftmann@27823
   771
  have "\<And>q. q \<le> n \<Longrightarrow> P q"
haftmann@27823
   772
  proof (induct n)
haftmann@27823
   773
    case (0 n)
krauss@26748
   774
    have "P 0" by (rule step) auto
krauss@26748
   775
    thus ?case using 0 by auto
krauss@26748
   776
  next
haftmann@27823
   777
    case (Suc m n)
haftmann@27823
   778
    then have "n \<le> m \<or> n = Suc m" by (simp add: le_Suc_eq)
krauss@26748
   779
    thus ?case
krauss@26748
   780
    proof
haftmann@27823
   781
      assume "n \<le> m" thus "P n" by (rule Suc(1))
krauss@26748
   782
    next
haftmann@27823
   783
      assume n: "n = Suc m"
haftmann@27823
   784
      show "P n"
haftmann@27823
   785
        by (rule step) (rule Suc(1), simp add: n le_simps)
krauss@26748
   786
    qed
krauss@26748
   787
  qed
haftmann@27823
   788
  then show "P n" by auto
krauss@26748
   789
qed
krauss@26748
   790
haftmann@27823
   791
lemma Least_Suc:
haftmann@27823
   792
     "[| P n; ~ P 0 |] ==> (LEAST n. P n) = Suc (LEAST m. P(Suc m))"
haftmann@27823
   793
  apply (case_tac "n", auto)
haftmann@27823
   794
  apply (frule LeastI)
haftmann@27823
   795
  apply (drule_tac P = "%x. P (Suc x) " in LeastI)
haftmann@27823
   796
  apply (subgoal_tac " (LEAST x. P x) \<le> Suc (LEAST x. P (Suc x))")
haftmann@27823
   797
  apply (erule_tac [2] Least_le)
haftmann@27823
   798
  apply (case_tac "LEAST x. P x", auto)
haftmann@27823
   799
  apply (drule_tac P = "%x. P (Suc x) " in Least_le)
haftmann@27823
   800
  apply (blast intro: order_antisym)
haftmann@27823
   801
  done
haftmann@27823
   802
haftmann@27823
   803
lemma Least_Suc2:
haftmann@27823
   804
   "[|P n; Q m; ~P 0; !k. P (Suc k) = Q k|] ==> Least P = Suc (Least Q)"
haftmann@27823
   805
  apply (erule (1) Least_Suc [THEN ssubst])
haftmann@27823
   806
  apply simp
haftmann@27823
   807
  done
haftmann@27823
   808
haftmann@27823
   809
lemma ex_least_nat_le: "\<not>P(0) \<Longrightarrow> P(n::nat) \<Longrightarrow> \<exists>k\<le>n. (\<forall>i<k. \<not>P i) & P(k)"
haftmann@27823
   810
  apply (cases n)
haftmann@27823
   811
   apply blast
haftmann@27823
   812
  apply (rule_tac x="LEAST k. P(k)" in exI)
haftmann@27823
   813
  apply (blast intro: Least_le dest: not_less_Least intro: LeastI_ex)
haftmann@27823
   814
  done
haftmann@27823
   815
haftmann@27823
   816
lemma ex_least_nat_less: "\<not>P(0) \<Longrightarrow> P(n::nat) \<Longrightarrow> \<exists>k<n. (\<forall>i\<le>k. \<not>P i) & P(k+1)"
huffman@30079
   817
  unfolding One_nat_def
haftmann@27823
   818
  apply (cases n)
haftmann@27823
   819
   apply blast
haftmann@27823
   820
  apply (frule (1) ex_least_nat_le)
haftmann@27823
   821
  apply (erule exE)
haftmann@27823
   822
  apply (case_tac k)
haftmann@27823
   823
   apply simp
haftmann@27823
   824
  apply (rename_tac k1)
haftmann@27823
   825
  apply (rule_tac x=k1 in exI)
haftmann@27823
   826
  apply (auto simp add: less_eq_Suc_le)
haftmann@27823
   827
  done
haftmann@27823
   828
krauss@26748
   829
lemma nat_less_induct:
krauss@26748
   830
  assumes "!!n. \<forall>m::nat. m < n --> P m ==> P n" shows "P n"
krauss@26748
   831
  using assms less_induct by blast
krauss@26748
   832
krauss@26748
   833
lemma measure_induct_rule [case_names less]:
krauss@26748
   834
  fixes f :: "'a \<Rightarrow> nat"
krauss@26748
   835
  assumes step: "\<And>x. (\<And>y. f y < f x \<Longrightarrow> P y) \<Longrightarrow> P x"
krauss@26748
   836
  shows "P a"
krauss@26748
   837
by (induct m\<equiv>"f a" arbitrary: a rule: less_induct) (auto intro: step)
krauss@26748
   838
krauss@26748
   839
text {* old style induction rules: *}
krauss@26748
   840
lemma measure_induct:
krauss@26748
   841
  fixes f :: "'a \<Rightarrow> nat"
krauss@26748
   842
  shows "(\<And>x. \<forall>y. f y < f x \<longrightarrow> P y \<Longrightarrow> P x) \<Longrightarrow> P a"
krauss@26748
   843
  by (rule measure_induct_rule [of f P a]) iprover
krauss@26748
   844
krauss@26748
   845
lemma full_nat_induct:
krauss@26748
   846
  assumes step: "(!!n. (ALL m. Suc m <= n --> P m) ==> P n)"
krauss@26748
   847
  shows "P n"
krauss@26748
   848
  by (rule less_induct) (auto intro: step simp:le_simps)
paulson@14267
   849
paulson@19870
   850
text{*An induction rule for estabilishing binary relations*}
wenzelm@22718
   851
lemma less_Suc_induct:
paulson@19870
   852
  assumes less:  "i < j"
paulson@19870
   853
     and  step:  "!!i. P i (Suc i)"
krauss@31714
   854
     and  trans: "!!i j k. i < j ==> j < k ==>  P i j ==> P j k ==> P i k"
paulson@19870
   855
  shows "P i j"
paulson@19870
   856
proof -
krauss@31714
   857
  from less obtain k where j: "j = Suc (i + k)" by (auto dest: less_imp_Suc_add)
wenzelm@22718
   858
  have "P i (Suc (i + k))"
paulson@19870
   859
  proof (induct k)
wenzelm@22718
   860
    case 0
wenzelm@22718
   861
    show ?case by (simp add: step)
paulson@19870
   862
  next
paulson@19870
   863
    case (Suc k)
krauss@31714
   864
    have "0 + i < Suc k + i" by (rule add_less_mono1) simp
krauss@31714
   865
    hence "i < Suc (i + k)" by (simp add: add_commute)
krauss@31714
   866
    from trans[OF this lessI Suc step]
krauss@31714
   867
    show ?case by simp
paulson@19870
   868
  qed
wenzelm@22718
   869
  thus "P i j" by (simp add: j)
paulson@19870
   870
qed
paulson@19870
   871
krauss@26748
   872
text {* The method of infinite descent, frequently used in number theory.
krauss@26748
   873
Provided by Roelof Oosterhuis.
krauss@26748
   874
$P(n)$ is true for all $n\in\mathbb{N}$ if
krauss@26748
   875
\begin{itemize}
krauss@26748
   876
  \item case ``0'': given $n=0$ prove $P(n)$,
krauss@26748
   877
  \item case ``smaller'': given $n>0$ and $\neg P(n)$ prove there exists
krauss@26748
   878
        a smaller integer $m$ such that $\neg P(m)$.
krauss@26748
   879
\end{itemize} *}
krauss@26748
   880
krauss@26748
   881
text{* A compact version without explicit base case: *}
krauss@26748
   882
lemma infinite_descent:
krauss@26748
   883
  "\<lbrakk> !!n::nat. \<not> P n \<Longrightarrow>  \<exists>m<n. \<not>  P m \<rbrakk> \<Longrightarrow>  P n"
krauss@26748
   884
by (induct n rule: less_induct, auto)
krauss@26748
   885
krauss@26748
   886
lemma infinite_descent0[case_names 0 smaller]: 
krauss@26748
   887
  "\<lbrakk> P 0; !!n. n>0 \<Longrightarrow> \<not> P n \<Longrightarrow> (\<exists>m::nat. m < n \<and> \<not>P m) \<rbrakk> \<Longrightarrow> P n"
krauss@26748
   888
by (rule infinite_descent) (case_tac "n>0", auto)
krauss@26748
   889
krauss@26748
   890
text {*
krauss@26748
   891
Infinite descent using a mapping to $\mathbb{N}$:
krauss@26748
   892
$P(x)$ is true for all $x\in D$ if there exists a $V: D \to \mathbb{N}$ and
krauss@26748
   893
\begin{itemize}
krauss@26748
   894
\item case ``0'': given $V(x)=0$ prove $P(x)$,
krauss@26748
   895
\item case ``smaller'': given $V(x)>0$ and $\neg P(x)$ prove there exists a $y \in D$ such that $V(y)<V(x)$ and $~\neg P(y)$.
krauss@26748
   896
\end{itemize}
krauss@26748
   897
NB: the proof also shows how to use the previous lemma. *}
krauss@26748
   898
krauss@26748
   899
corollary infinite_descent0_measure [case_names 0 smaller]:
krauss@26748
   900
  assumes A0: "!!x. V x = (0::nat) \<Longrightarrow> P x"
krauss@26748
   901
    and   A1: "!!x. V x > 0 \<Longrightarrow> \<not>P x \<Longrightarrow> (\<exists>y. V y < V x \<and> \<not>P y)"
krauss@26748
   902
  shows "P x"
krauss@26748
   903
proof -
krauss@26748
   904
  obtain n where "n = V x" by auto
krauss@26748
   905
  moreover have "\<And>x. V x = n \<Longrightarrow> P x"
krauss@26748
   906
  proof (induct n rule: infinite_descent0)
krauss@26748
   907
    case 0 -- "i.e. $V(x) = 0$"
krauss@26748
   908
    with A0 show "P x" by auto
krauss@26748
   909
  next -- "now $n>0$ and $P(x)$ does not hold for some $x$ with $V(x)=n$"
krauss@26748
   910
    case (smaller n)
krauss@26748
   911
    then obtain x where vxn: "V x = n " and "V x > 0 \<and> \<not> P x" by auto
krauss@26748
   912
    with A1 obtain y where "V y < V x \<and> \<not> P y" by auto
krauss@26748
   913
    with vxn obtain m where "m = V y \<and> m<n \<and> \<not> P y" by auto
krauss@26748
   914
    then show ?case by auto
krauss@26748
   915
  qed
krauss@26748
   916
  ultimately show "P x" by auto
krauss@26748
   917
qed
krauss@26748
   918
krauss@26748
   919
text{* Again, without explicit base case: *}
krauss@26748
   920
lemma infinite_descent_measure:
krauss@26748
   921
assumes "!!x. \<not> P x \<Longrightarrow> \<exists>y. (V::'a\<Rightarrow>nat) y < V x \<and> \<not> P y" shows "P x"
krauss@26748
   922
proof -
krauss@26748
   923
  from assms obtain n where "n = V x" by auto
krauss@26748
   924
  moreover have "!!x. V x = n \<Longrightarrow> P x"
krauss@26748
   925
  proof (induct n rule: infinite_descent, auto)
krauss@26748
   926
    fix x assume "\<not> P x"
krauss@26748
   927
    with assms show "\<exists>m < V x. \<exists>y. V y = m \<and> \<not> P y" by auto
krauss@26748
   928
  qed
krauss@26748
   929
  ultimately show "P x" by auto
krauss@26748
   930
qed
krauss@26748
   931
paulson@14267
   932
text {* A [clumsy] way of lifting @{text "<"}
paulson@14267
   933
  monotonicity to @{text "\<le>"} monotonicity *}
paulson@14267
   934
lemma less_mono_imp_le_mono:
nipkow@24438
   935
  "\<lbrakk> !!i j::nat. i < j \<Longrightarrow> f i < f j; i \<le> j \<rbrakk> \<Longrightarrow> f i \<le> ((f j)::nat)"
nipkow@24438
   936
by (simp add: order_le_less) (blast)
nipkow@24438
   937
paulson@14267
   938
paulson@14267
   939
text {* non-strict, in 1st argument *}
paulson@14267
   940
lemma add_le_mono1: "i \<le> j ==> i + k \<le> j + (k::nat)"
nipkow@24438
   941
by (rule add_right_mono)
paulson@14267
   942
paulson@14267
   943
text {* non-strict, in both arguments *}
paulson@14267
   944
lemma add_le_mono: "[| i \<le> j;  k \<le> l |] ==> i + k \<le> j + (l::nat)"
nipkow@24438
   945
by (rule add_mono)
paulson@14267
   946
paulson@14267
   947
lemma le_add2: "n \<le> ((m + n)::nat)"
nipkow@24438
   948
by (insert add_right_mono [of 0 m n], simp)
berghofe@13449
   949
paulson@14267
   950
lemma le_add1: "n \<le> ((n + m)::nat)"
nipkow@24438
   951
by (simp add: add_commute, rule le_add2)
berghofe@13449
   952
berghofe@13449
   953
lemma less_add_Suc1: "i < Suc (i + m)"
nipkow@24438
   954
by (rule le_less_trans, rule le_add1, rule lessI)
berghofe@13449
   955
berghofe@13449
   956
lemma less_add_Suc2: "i < Suc (m + i)"
nipkow@24438
   957
by (rule le_less_trans, rule le_add2, rule lessI)
berghofe@13449
   958
paulson@14267
   959
lemma less_iff_Suc_add: "(m < n) = (\<exists>k. n = Suc (m + k))"
nipkow@24438
   960
by (iprover intro!: less_add_Suc1 less_imp_Suc_add)
berghofe@13449
   961
paulson@14267
   962
lemma trans_le_add1: "(i::nat) \<le> j ==> i \<le> j + m"
nipkow@24438
   963
by (rule le_trans, assumption, rule le_add1)
berghofe@13449
   964
paulson@14267
   965
lemma trans_le_add2: "(i::nat) \<le> j ==> i \<le> m + j"
nipkow@24438
   966
by (rule le_trans, assumption, rule le_add2)
berghofe@13449
   967
berghofe@13449
   968
lemma trans_less_add1: "(i::nat) < j ==> i < j + m"
nipkow@24438
   969
by (rule less_le_trans, assumption, rule le_add1)
berghofe@13449
   970
berghofe@13449
   971
lemma trans_less_add2: "(i::nat) < j ==> i < m + j"
nipkow@24438
   972
by (rule less_le_trans, assumption, rule le_add2)
berghofe@13449
   973
berghofe@13449
   974
lemma add_lessD1: "i + j < (k::nat) ==> i < k"
nipkow@24438
   975
apply (rule le_less_trans [of _ "i+j"])
nipkow@24438
   976
apply (simp_all add: le_add1)
nipkow@24438
   977
done
berghofe@13449
   978
berghofe@13449
   979
lemma not_add_less1 [iff]: "~ (i + j < (i::nat))"
nipkow@24438
   980
apply (rule notI)
wenzelm@26335
   981
apply (drule add_lessD1)
wenzelm@26335
   982
apply (erule less_irrefl [THEN notE])
nipkow@24438
   983
done
berghofe@13449
   984
berghofe@13449
   985
lemma not_add_less2 [iff]: "~ (j + i < (i::nat))"
krauss@26748
   986
by (simp add: add_commute)
berghofe@13449
   987
paulson@14267
   988
lemma add_leD1: "m + k \<le> n ==> m \<le> (n::nat)"
nipkow@24438
   989
apply (rule order_trans [of _ "m+k"])
nipkow@24438
   990
apply (simp_all add: le_add1)
nipkow@24438
   991
done
berghofe@13449
   992
paulson@14267
   993
lemma add_leD2: "m + k \<le> n ==> k \<le> (n::nat)"
nipkow@24438
   994
apply (simp add: add_commute)
nipkow@24438
   995
apply (erule add_leD1)
nipkow@24438
   996
done
berghofe@13449
   997
paulson@14267
   998
lemma add_leE: "(m::nat) + k \<le> n ==> (m \<le> n ==> k \<le> n ==> R) ==> R"
nipkow@24438
   999
by (blast dest: add_leD1 add_leD2)
berghofe@13449
  1000
berghofe@13449
  1001
text {* needs @{text "!!k"} for @{text add_ac} to work *}
berghofe@13449
  1002
lemma less_add_eq_less: "!!k::nat. k < l ==> m + l = k + n ==> m < n"
nipkow@24438
  1003
by (force simp del: add_Suc_right
berghofe@13449
  1004
    simp add: less_iff_Suc_add add_Suc_right [symmetric] add_ac)
berghofe@13449
  1005
berghofe@13449
  1006
haftmann@26072
  1007
subsubsection {* More results about difference *}
berghofe@13449
  1008
berghofe@13449
  1009
text {* Addition is the inverse of subtraction:
paulson@14267
  1010
  if @{term "n \<le> m"} then @{term "n + (m - n) = m"}. *}
berghofe@13449
  1011
lemma add_diff_inverse: "~  m < n ==> n + (m - n) = (m::nat)"
nipkow@24438
  1012
by (induct m n rule: diff_induct) simp_all
berghofe@13449
  1013
paulson@14267
  1014
lemma le_add_diff_inverse [simp]: "n \<le> m ==> n + (m - n) = (m::nat)"
nipkow@24438
  1015
by (simp add: add_diff_inverse linorder_not_less)
berghofe@13449
  1016
paulson@14267
  1017
lemma le_add_diff_inverse2 [simp]: "n \<le> m ==> (m - n) + n = (m::nat)"
krauss@26748
  1018
by (simp add: add_commute)
berghofe@13449
  1019
paulson@14267
  1020
lemma Suc_diff_le: "n \<le> m ==> Suc m - n = Suc (m - n)"
nipkow@24438
  1021
by (induct m n rule: diff_induct) simp_all
berghofe@13449
  1022
berghofe@13449
  1023
lemma diff_less_Suc: "m - n < Suc m"
nipkow@24438
  1024
apply (induct m n rule: diff_induct)
nipkow@24438
  1025
apply (erule_tac [3] less_SucE)
nipkow@24438
  1026
apply (simp_all add: less_Suc_eq)
nipkow@24438
  1027
done
berghofe@13449
  1028
paulson@14267
  1029
lemma diff_le_self [simp]: "m - n \<le> (m::nat)"
nipkow@24438
  1030
by (induct m n rule: diff_induct) (simp_all add: le_SucI)
berghofe@13449
  1031
haftmann@26072
  1032
lemma le_iff_add: "(m::nat) \<le> n = (\<exists>k. n = m + k)"
haftmann@26072
  1033
  by (auto simp: le_add1 dest!: le_add_diff_inverse sym [of _ n])
haftmann@26072
  1034
berghofe@13449
  1035
lemma less_imp_diff_less: "(j::nat) < k ==> j - n < k"
nipkow@24438
  1036
by (rule le_less_trans, rule diff_le_self)
berghofe@13449
  1037
berghofe@13449
  1038
lemma diff_Suc_less [simp]: "0<n ==> n - Suc i < n"
nipkow@24438
  1039
by (cases n) (auto simp add: le_simps)
berghofe@13449
  1040
paulson@14267
  1041
lemma diff_add_assoc: "k \<le> (j::nat) ==> (i + j) - k = i + (j - k)"
nipkow@24438
  1042
by (induct j k rule: diff_induct) simp_all
berghofe@13449
  1043
paulson@14267
  1044
lemma diff_add_assoc2: "k \<le> (j::nat) ==> (j + i) - k = (j - k) + i"
nipkow@24438
  1045
by (simp add: add_commute diff_add_assoc)
berghofe@13449
  1046
paulson@14267
  1047
lemma le_imp_diff_is_add: "i \<le> (j::nat) ==> (j - i = k) = (j = k + i)"
nipkow@24438
  1048
by (auto simp add: diff_add_inverse2)
berghofe@13449
  1049
paulson@14267
  1050
lemma diff_is_0_eq [simp]: "((m::nat) - n = 0) = (m \<le> n)"
nipkow@24438
  1051
by (induct m n rule: diff_induct) simp_all
berghofe@13449
  1052
paulson@14267
  1053
lemma diff_is_0_eq' [simp]: "m \<le> n ==> (m::nat) - n = 0"
nipkow@24438
  1054
by (rule iffD2, rule diff_is_0_eq)
berghofe@13449
  1055
berghofe@13449
  1056
lemma zero_less_diff [simp]: "(0 < n - (m::nat)) = (m < n)"
nipkow@24438
  1057
by (induct m n rule: diff_induct) simp_all
berghofe@13449
  1058
wenzelm@22718
  1059
lemma less_imp_add_positive:
wenzelm@22718
  1060
  assumes "i < j"
wenzelm@22718
  1061
  shows "\<exists>k::nat. 0 < k & i + k = j"
wenzelm@22718
  1062
proof
wenzelm@22718
  1063
  from assms show "0 < j - i & i + (j - i) = j"
huffman@23476
  1064
    by (simp add: order_less_imp_le)
wenzelm@22718
  1065
qed
wenzelm@9436
  1066
haftmann@26072
  1067
text {* a nice rewrite for bounded subtraction *}
haftmann@26072
  1068
lemma nat_minus_add_max:
haftmann@26072
  1069
  fixes n m :: nat
haftmann@26072
  1070
  shows "n - m + m = max n m"
haftmann@26072
  1071
    by (simp add: max_def not_le order_less_imp_le)
berghofe@13449
  1072
haftmann@26072
  1073
lemma nat_diff_split:
haftmann@26072
  1074
  "P(a - b::nat) = ((a<b --> P 0) & (ALL d. a = b + d --> P d))"
haftmann@26072
  1075
    -- {* elimination of @{text -} on @{text nat} *}
haftmann@26072
  1076
by (cases "a < b")
haftmann@26072
  1077
  (auto simp add: diff_is_0_eq [THEN iffD2] diff_add_inverse
haftmann@26072
  1078
    not_less le_less dest!: sym [of a] sym [of b] add_eq_self_zero)
berghofe@13449
  1079
haftmann@26072
  1080
lemma nat_diff_split_asm:
haftmann@26072
  1081
  "P(a - b::nat) = (~ (a < b & ~ P 0 | (EX d. a = b + d & ~ P d)))"
haftmann@26072
  1082
    -- {* elimination of @{text -} on @{text nat} in assumptions *}
haftmann@26072
  1083
by (auto split: nat_diff_split)
berghofe@13449
  1084
berghofe@13449
  1085
haftmann@26072
  1086
subsubsection {* Monotonicity of Multiplication *}
berghofe@13449
  1087
paulson@14267
  1088
lemma mult_le_mono1: "i \<le> (j::nat) ==> i * k \<le> j * k"
nipkow@24438
  1089
by (simp add: mult_right_mono)
berghofe@13449
  1090
paulson@14267
  1091
lemma mult_le_mono2: "i \<le> (j::nat) ==> k * i \<le> k * j"
nipkow@24438
  1092
by (simp add: mult_left_mono)
berghofe@13449
  1093
paulson@14267
  1094
text {* @{text "\<le>"} monotonicity, BOTH arguments *}
paulson@14267
  1095
lemma mult_le_mono: "i \<le> (j::nat) ==> k \<le> l ==> i * k \<le> j * l"
nipkow@24438
  1096
by (simp add: mult_mono)
berghofe@13449
  1097
berghofe@13449
  1098
lemma mult_less_mono1: "(i::nat) < j ==> 0 < k ==> i * k < j * k"
nipkow@24438
  1099
by (simp add: mult_strict_right_mono)
berghofe@13449
  1100
paulson@14266
  1101
text{*Differs from the standard @{text zero_less_mult_iff} in that
paulson@14266
  1102
      there are no negative numbers.*}
paulson@14266
  1103
lemma nat_0_less_mult_iff [simp]: "(0 < (m::nat) * n) = (0 < m & 0 < n)"
berghofe@13449
  1104
  apply (induct m)
wenzelm@22718
  1105
   apply simp
wenzelm@22718
  1106
  apply (case_tac n)
wenzelm@22718
  1107
   apply simp_all
berghofe@13449
  1108
  done
berghofe@13449
  1109
huffman@30079
  1110
lemma one_le_mult_iff [simp]: "(Suc 0 \<le> m * n) = (Suc 0 \<le> m & Suc 0 \<le> n)"
berghofe@13449
  1111
  apply (induct m)
wenzelm@22718
  1112
   apply simp
wenzelm@22718
  1113
  apply (case_tac n)
wenzelm@22718
  1114
   apply simp_all
berghofe@13449
  1115
  done
berghofe@13449
  1116
paulson@14341
  1117
lemma mult_less_cancel2 [simp]: "((m::nat) * k < n * k) = (0 < k & m < n)"
berghofe@13449
  1118
  apply (safe intro!: mult_less_mono1)
paulson@14208
  1119
  apply (case_tac k, auto)
berghofe@13449
  1120
  apply (simp del: le_0_eq add: linorder_not_le [symmetric])
berghofe@13449
  1121
  apply (blast intro: mult_le_mono1)
berghofe@13449
  1122
  done
berghofe@13449
  1123
berghofe@13449
  1124
lemma mult_less_cancel1 [simp]: "(k * (m::nat) < k * n) = (0 < k & m < n)"
nipkow@24438
  1125
by (simp add: mult_commute [of k])
berghofe@13449
  1126
paulson@14267
  1127
lemma mult_le_cancel1 [simp]: "(k * (m::nat) \<le> k * n) = (0 < k --> m \<le> n)"
nipkow@24438
  1128
by (simp add: linorder_not_less [symmetric], auto)
berghofe@13449
  1129
paulson@14267
  1130
lemma mult_le_cancel2 [simp]: "((m::nat) * k \<le> n * k) = (0 < k --> m \<le> n)"
nipkow@24438
  1131
by (simp add: linorder_not_less [symmetric], auto)
berghofe@13449
  1132
berghofe@13449
  1133
lemma Suc_mult_less_cancel1: "(Suc k * m < Suc k * n) = (m < n)"
nipkow@24438
  1134
by (subst mult_less_cancel1) simp
berghofe@13449
  1135
paulson@14267
  1136
lemma Suc_mult_le_cancel1: "(Suc k * m \<le> Suc k * n) = (m \<le> n)"
nipkow@24438
  1137
by (subst mult_le_cancel1) simp
berghofe@13449
  1138
haftmann@26072
  1139
lemma le_square: "m \<le> m * (m::nat)"
haftmann@26072
  1140
  by (cases m) (auto intro: le_add1)
haftmann@26072
  1141
haftmann@26072
  1142
lemma le_cube: "(m::nat) \<le> m * (m * m)"
haftmann@26072
  1143
  by (cases m) (auto intro: le_add1)
berghofe@13449
  1144
berghofe@13449
  1145
text {* Lemma for @{text gcd} *}
huffman@30128
  1146
lemma mult_eq_self_implies_10: "(m::nat) = m * n ==> n = 1 | m = 0"
berghofe@13449
  1147
  apply (drule sym)
berghofe@13449
  1148
  apply (rule disjCI)
berghofe@13449
  1149
  apply (rule nat_less_cases, erule_tac [2] _)
paulson@25157
  1150
   apply (drule_tac [2] mult_less_mono2)
nipkow@25162
  1151
    apply (auto)
berghofe@13449
  1152
  done
wenzelm@9436
  1153
haftmann@26072
  1154
text {* the lattice order on @{typ nat} *}
haftmann@24995
  1155
haftmann@26072
  1156
instantiation nat :: distrib_lattice
haftmann@26072
  1157
begin
haftmann@24995
  1158
haftmann@26072
  1159
definition
haftmann@26072
  1160
  "(inf \<Colon> nat \<Rightarrow> nat \<Rightarrow> nat) = min"
haftmann@24995
  1161
haftmann@26072
  1162
definition
haftmann@26072
  1163
  "(sup \<Colon> nat \<Rightarrow> nat \<Rightarrow> nat) = max"
haftmann@24995
  1164
haftmann@26072
  1165
instance by intro_classes
haftmann@26072
  1166
  (auto simp add: inf_nat_def sup_nat_def max_def not_le min_def
haftmann@26072
  1167
    intro: order_less_imp_le antisym elim!: order_trans order_less_trans)
haftmann@24995
  1168
haftmann@26072
  1169
end
haftmann@24995
  1170
haftmann@24995
  1171
haftmann@30954
  1172
subsection {* Natural operation of natural numbers on functions *}
haftmann@30954
  1173
haftmann@30971
  1174
text {*
haftmann@30971
  1175
  We use the same logical constant for the power operations on
haftmann@30971
  1176
  functions and relations, in order to share the same syntax.
haftmann@30971
  1177
*}
haftmann@30971
  1178
haftmann@30971
  1179
consts compow :: "nat \<Rightarrow> ('a \<Rightarrow> 'b) \<Rightarrow> ('a \<Rightarrow> 'b)"
haftmann@30971
  1180
haftmann@30971
  1181
abbreviation compower :: "('a \<Rightarrow> 'b) \<Rightarrow> nat \<Rightarrow> 'a \<Rightarrow> 'b" (infixr "^^" 80) where
haftmann@30971
  1182
  "f ^^ n \<equiv> compow n f"
haftmann@30971
  1183
haftmann@30971
  1184
notation (latex output)
haftmann@30971
  1185
  compower ("(_\<^bsup>_\<^esup>)" [1000] 1000)
haftmann@30971
  1186
haftmann@30971
  1187
notation (HTML output)
haftmann@30971
  1188
  compower ("(_\<^bsup>_\<^esup>)" [1000] 1000)
haftmann@30971
  1189
haftmann@30971
  1190
text {* @{text "f ^^ n = f o ... o f"}, the n-fold composition of @{text f} *}
haftmann@30971
  1191
haftmann@30971
  1192
overloading
haftmann@30971
  1193
  funpow == "compow :: nat \<Rightarrow> ('a \<Rightarrow> 'a) \<Rightarrow> ('a \<Rightarrow> 'a)"
haftmann@30971
  1194
begin
haftmann@30954
  1195
haftmann@30954
  1196
primrec funpow :: "nat \<Rightarrow> ('a \<Rightarrow> 'a) \<Rightarrow> 'a \<Rightarrow> 'a" where
haftmann@30954
  1197
    "funpow 0 f = id"
haftmann@30954
  1198
  | "funpow (Suc n) f = f o funpow n f"
haftmann@30954
  1199
haftmann@30971
  1200
end
haftmann@30971
  1201
haftmann@30971
  1202
text {* for code generation *}
haftmann@30971
  1203
haftmann@30971
  1204
definition funpow :: "nat \<Rightarrow> ('a \<Rightarrow> 'a) \<Rightarrow> 'a \<Rightarrow> 'a" where
haftmann@31998
  1205
  funpow_code_def [code_post]: "funpow = compow"
haftmann@30954
  1206
haftmann@31998
  1207
lemmas [code_unfold] = funpow_code_def [symmetric]
haftmann@30954
  1208
haftmann@30971
  1209
lemma [code]:
haftmann@30971
  1210
  "funpow 0 f = id"
haftmann@30971
  1211
  "funpow (Suc n) f = f o funpow n f"
haftmann@30971
  1212
  unfolding funpow_code_def by simp_all
haftmann@30971
  1213
haftmann@30975
  1214
hide (open) const funpow
haftmann@30954
  1215
haftmann@30954
  1216
lemma funpow_add:
haftmann@30971
  1217
  "f ^^ (m + n) = f ^^ m \<circ> f ^^ n"
haftmann@30954
  1218
  by (induct m) simp_all
haftmann@30954
  1219
haftmann@30954
  1220
lemma funpow_swap1:
haftmann@30971
  1221
  "f ((f ^^ n) x) = (f ^^ n) (f x)"
haftmann@30954
  1222
proof -
haftmann@30971
  1223
  have "f ((f ^^ n) x) = (f ^^ (n + 1)) x" by simp
haftmann@30971
  1224
  also have "\<dots>  = (f ^^ n o f ^^ 1) x" by (simp only: funpow_add)
haftmann@30971
  1225
  also have "\<dots> = (f ^^ n) (f x)" by simp
haftmann@30954
  1226
  finally show ?thesis .
haftmann@30954
  1227
qed
haftmann@30954
  1228
haftmann@30954
  1229
haftmann@25193
  1230
subsection {* Embedding of the Naturals into any
haftmann@25193
  1231
  @{text semiring_1}: @{term of_nat} *}
haftmann@24196
  1232
haftmann@24196
  1233
context semiring_1
haftmann@24196
  1234
begin
haftmann@24196
  1235
haftmann@25559
  1236
primrec
haftmann@25559
  1237
  of_nat :: "nat \<Rightarrow> 'a"
haftmann@25559
  1238
where
haftmann@25559
  1239
  of_nat_0:     "of_nat 0 = 0"
haftmann@25559
  1240
  | of_nat_Suc: "of_nat (Suc m) = 1 + of_nat m"
haftmann@25193
  1241
haftmann@25193
  1242
lemma of_nat_1 [simp]: "of_nat 1 = 1"
huffman@30079
  1243
  unfolding One_nat_def by simp
haftmann@25193
  1244
haftmann@25193
  1245
lemma of_nat_add [simp]: "of_nat (m + n) = of_nat m + of_nat n"
haftmann@25193
  1246
  by (induct m) (simp_all add: add_ac)
haftmann@25193
  1247
haftmann@25193
  1248
lemma of_nat_mult: "of_nat (m * n) = of_nat m * of_nat n"
haftmann@25193
  1249
  by (induct m) (simp_all add: add_ac left_distrib)
haftmann@25193
  1250
haftmann@28514
  1251
primrec of_nat_aux :: "('a \<Rightarrow> 'a) \<Rightarrow> nat \<Rightarrow> 'a \<Rightarrow> 'a" where
haftmann@28514
  1252
  "of_nat_aux inc 0 i = i"
haftmann@28514
  1253
  | "of_nat_aux inc (Suc n) i = of_nat_aux inc n (inc i)" -- {* tail recursive *}
haftmann@25928
  1254
haftmann@30966
  1255
lemma of_nat_code:
haftmann@28514
  1256
  "of_nat n = of_nat_aux (\<lambda>i. i + 1) n 0"
haftmann@28514
  1257
proof (induct n)
haftmann@28514
  1258
  case 0 then show ?case by simp
haftmann@28514
  1259
next
haftmann@28514
  1260
  case (Suc n)
haftmann@28514
  1261
  have "\<And>i. of_nat_aux (\<lambda>i. i + 1) n (i + 1) = of_nat_aux (\<lambda>i. i + 1) n i + 1"
haftmann@28514
  1262
    by (induct n) simp_all
haftmann@28514
  1263
  from this [of 0] have "of_nat_aux (\<lambda>i. i + 1) n 1 = of_nat_aux (\<lambda>i. i + 1) n 0 + 1"
haftmann@28514
  1264
    by simp
haftmann@28514
  1265
  with Suc show ?case by (simp add: add_commute)
haftmann@28514
  1266
qed
haftmann@30966
  1267
haftmann@24196
  1268
end
haftmann@24196
  1269
haftmann@31998
  1270
declare of_nat_code [code, code_unfold, code_inline del]
haftmann@30966
  1271
haftmann@26072
  1272
text{*Class for unital semirings with characteristic zero.
haftmann@26072
  1273
 Includes non-ordered rings like the complex numbers.*}
haftmann@26072
  1274
haftmann@26072
  1275
class semiring_char_0 = semiring_1 +
haftmann@26072
  1276
  assumes of_nat_eq_iff [simp]: "of_nat m = of_nat n \<longleftrightarrow> m = n"
haftmann@26072
  1277
begin
haftmann@26072
  1278
haftmann@26072
  1279
text{*Special cases where either operand is zero*}
haftmann@26072
  1280
haftmann@26072
  1281
lemma of_nat_0_eq_iff [simp, noatp]: "0 = of_nat n \<longleftrightarrow> 0 = n"
huffman@31024
  1282
  by (rule of_nat_eq_iff [of 0 n, unfolded of_nat_0])
haftmann@26072
  1283
haftmann@26072
  1284
lemma of_nat_eq_0_iff [simp, noatp]: "of_nat m = 0 \<longleftrightarrow> m = 0"
huffman@31024
  1285
  by (rule of_nat_eq_iff [of m 0, unfolded of_nat_0])
haftmann@26072
  1286
haftmann@26072
  1287
lemma inj_of_nat: "inj of_nat"
haftmann@26072
  1288
  by (simp add: inj_on_def)
haftmann@26072
  1289
haftmann@26072
  1290
end
haftmann@26072
  1291
haftmann@35028
  1292
context linordered_semidom
haftmann@25193
  1293
begin
haftmann@25193
  1294
haftmann@25193
  1295
lemma zero_le_imp_of_nat: "0 \<le> of_nat m"
haftmann@25193
  1296
  apply (induct m, simp_all)
haftmann@25193
  1297
  apply (erule order_trans)
haftmann@25193
  1298
  apply (rule ord_le_eq_trans [OF _ add_commute])
haftmann@25193
  1299
  apply (rule less_add_one [THEN less_imp_le])
haftmann@25193
  1300
  done
haftmann@25193
  1301
haftmann@25193
  1302
lemma less_imp_of_nat_less: "m < n \<Longrightarrow> of_nat m < of_nat n"
haftmann@25193
  1303
  apply (induct m n rule: diff_induct, simp_all)
haftmann@25193
  1304
  apply (insert add_less_le_mono [OF zero_less_one zero_le_imp_of_nat], force)
haftmann@25193
  1305
  done
haftmann@25193
  1306
haftmann@25193
  1307
lemma of_nat_less_imp_less: "of_nat m < of_nat n \<Longrightarrow> m < n"
haftmann@25193
  1308
  apply (induct m n rule: diff_induct, simp_all)
haftmann@25193
  1309
  apply (insert zero_le_imp_of_nat)
haftmann@25193
  1310
  apply (force simp add: not_less [symmetric])
haftmann@25193
  1311
  done
haftmann@25193
  1312
haftmann@25193
  1313
lemma of_nat_less_iff [simp]: "of_nat m < of_nat n \<longleftrightarrow> m < n"
haftmann@25193
  1314
  by (blast intro: of_nat_less_imp_less less_imp_of_nat_less)
haftmann@25193
  1315
haftmann@26072
  1316
lemma of_nat_le_iff [simp]: "of_nat m \<le> of_nat n \<longleftrightarrow> m \<le> n"
haftmann@26072
  1317
  by (simp add: not_less [symmetric] linorder_not_less [symmetric])
haftmann@25193
  1318
haftmann@35028
  1319
text{*Every @{text linordered_semidom} has characteristic zero.*}
haftmann@25193
  1320
haftmann@26072
  1321
subclass semiring_char_0
haftmann@28823
  1322
  proof qed (simp add: eq_iff order_eq_iff)
haftmann@25193
  1323
haftmann@25193
  1324
text{*Special cases where either operand is zero*}
haftmann@25193
  1325
haftmann@25193
  1326
lemma of_nat_0_le_iff [simp]: "0 \<le> of_nat n"
haftmann@25193
  1327
  by (rule of_nat_le_iff [of 0, simplified])
haftmann@25193
  1328
haftmann@25193
  1329
lemma of_nat_le_0_iff [simp, noatp]: "of_nat m \<le> 0 \<longleftrightarrow> m = 0"
haftmann@25193
  1330
  by (rule of_nat_le_iff [of _ 0, simplified])
haftmann@25193
  1331
haftmann@26072
  1332
lemma of_nat_0_less_iff [simp]: "0 < of_nat n \<longleftrightarrow> 0 < n"
haftmann@26072
  1333
  by (rule of_nat_less_iff [of 0, simplified])
haftmann@26072
  1334
haftmann@26072
  1335
lemma of_nat_less_0_iff [simp]: "\<not> of_nat m < 0"
haftmann@26072
  1336
  by (rule of_nat_less_iff [of _ 0, simplified])
haftmann@26072
  1337
haftmann@26072
  1338
end
haftmann@26072
  1339
haftmann@26072
  1340
context ring_1
haftmann@26072
  1341
begin
haftmann@26072
  1342
haftmann@26072
  1343
lemma of_nat_diff: "n \<le> m \<Longrightarrow> of_nat (m - n) = of_nat m - of_nat n"
nipkow@29667
  1344
by (simp add: algebra_simps of_nat_add [symmetric])
haftmann@26072
  1345
haftmann@26072
  1346
end
haftmann@26072
  1347
haftmann@35028
  1348
context linordered_idom
haftmann@26072
  1349
begin
haftmann@26072
  1350
haftmann@26072
  1351
lemma abs_of_nat [simp]: "\<bar>of_nat n\<bar> = of_nat n"
haftmann@26072
  1352
  unfolding abs_if by auto
haftmann@26072
  1353
haftmann@25193
  1354
end
haftmann@25193
  1355
haftmann@25193
  1356
lemma of_nat_id [simp]: "of_nat n = n"
huffman@30079
  1357
  by (induct n) (auto simp add: One_nat_def)
haftmann@25193
  1358
haftmann@25193
  1359
lemma of_nat_eq_id [simp]: "of_nat = id"
haftmann@25193
  1360
  by (auto simp add: expand_fun_eq)
haftmann@25193
  1361
haftmann@25193
  1362
haftmann@26149
  1363
subsection {* The Set of Natural Numbers *}
haftmann@25193
  1364
haftmann@26072
  1365
context semiring_1
haftmann@25193
  1366
begin
haftmann@25193
  1367
haftmann@26072
  1368
definition
haftmann@26072
  1369
  Nats  :: "'a set" where
haftmann@28562
  1370
  [code del]: "Nats = range of_nat"
haftmann@26072
  1371
haftmann@26072
  1372
notation (xsymbols)
haftmann@26072
  1373
  Nats  ("\<nat>")
haftmann@25193
  1374
haftmann@26072
  1375
lemma of_nat_in_Nats [simp]: "of_nat n \<in> \<nat>"
haftmann@26072
  1376
  by (simp add: Nats_def)
haftmann@26072
  1377
haftmann@26072
  1378
lemma Nats_0 [simp]: "0 \<in> \<nat>"
haftmann@26072
  1379
apply (simp add: Nats_def)
haftmann@26072
  1380
apply (rule range_eqI)
haftmann@26072
  1381
apply (rule of_nat_0 [symmetric])
haftmann@26072
  1382
done
haftmann@25193
  1383
haftmann@26072
  1384
lemma Nats_1 [simp]: "1 \<in> \<nat>"
haftmann@26072
  1385
apply (simp add: Nats_def)
haftmann@26072
  1386
apply (rule range_eqI)
haftmann@26072
  1387
apply (rule of_nat_1 [symmetric])
haftmann@26072
  1388
done
haftmann@25193
  1389
haftmann@26072
  1390
lemma Nats_add [simp]: "a \<in> \<nat> \<Longrightarrow> b \<in> \<nat> \<Longrightarrow> a + b \<in> \<nat>"
haftmann@26072
  1391
apply (auto simp add: Nats_def)
haftmann@26072
  1392
apply (rule range_eqI)
haftmann@26072
  1393
apply (rule of_nat_add [symmetric])
haftmann@26072
  1394
done
haftmann@26072
  1395
haftmann@26072
  1396
lemma Nats_mult [simp]: "a \<in> \<nat> \<Longrightarrow> b \<in> \<nat> \<Longrightarrow> a * b \<in> \<nat>"
haftmann@26072
  1397
apply (auto simp add: Nats_def)
haftmann@26072
  1398
apply (rule range_eqI)
haftmann@26072
  1399
apply (rule of_nat_mult [symmetric])
haftmann@26072
  1400
done
haftmann@25193
  1401
haftmann@25193
  1402
end
haftmann@25193
  1403
haftmann@25193
  1404
wenzelm@21243
  1405
subsection {* Further Arithmetic Facts Concerning the Natural Numbers *}
wenzelm@21243
  1406
haftmann@22845
  1407
lemma subst_equals:
haftmann@22845
  1408
  assumes 1: "t = s" and 2: "u = t"
haftmann@22845
  1409
  shows "u = s"
haftmann@22845
  1410
  using 2 1 by (rule trans)
haftmann@22845
  1411
haftmann@30686
  1412
setup Arith_Data.setup
haftmann@30686
  1413
haftmann@30496
  1414
use "Tools/nat_arith.ML"
haftmann@30496
  1415
declaration {* K Nat_Arith.setup *}
wenzelm@24091
  1416
wenzelm@24091
  1417
use "Tools/lin_arith.ML"
haftmann@31100
  1418
setup {* Lin_Arith.global_setup *}
haftmann@30686
  1419
declaration {* K Lin_Arith.setup *}
wenzelm@24091
  1420
wenzelm@21243
  1421
lemmas [arith_split] = nat_diff_split split_min split_max
wenzelm@21243
  1422
nipkow@27625
  1423
context order
nipkow@27625
  1424
begin
nipkow@27625
  1425
nipkow@27625
  1426
lemma lift_Suc_mono_le:
krauss@27627
  1427
  assumes mono: "!!n. f n \<le> f(Suc n)" and "n\<le>n'"
krauss@27627
  1428
  shows "f n \<le> f n'"
krauss@27627
  1429
proof (cases "n < n'")
krauss@27627
  1430
  case True
krauss@27627
  1431
  thus ?thesis
krauss@27627
  1432
    by (induct n n' rule: less_Suc_induct[consumes 1]) (auto intro: mono)
krauss@27627
  1433
qed (insert `n \<le> n'`, auto) -- {*trivial for @{prop "n = n'"} *}
nipkow@27625
  1434
nipkow@27625
  1435
lemma lift_Suc_mono_less:
krauss@27627
  1436
  assumes mono: "!!n. f n < f(Suc n)" and "n < n'"
krauss@27627
  1437
  shows "f n < f n'"
krauss@27627
  1438
using `n < n'`
krauss@27627
  1439
by (induct n n' rule: less_Suc_induct[consumes 1]) (auto intro: mono)
nipkow@27625
  1440
nipkow@27789
  1441
lemma lift_Suc_mono_less_iff:
nipkow@27789
  1442
  "(!!n. f n < f(Suc n)) \<Longrightarrow> f(n) < f(m) \<longleftrightarrow> n<m"
nipkow@27789
  1443
by(blast intro: less_asym' lift_Suc_mono_less[of f]
nipkow@27789
  1444
         dest: linorder_not_less[THEN iffD1] le_eq_less_or_eq[THEN iffD1])
nipkow@27789
  1445
nipkow@27625
  1446
end
nipkow@27625
  1447
nipkow@29879
  1448
lemma mono_iff_le_Suc: "mono f = (\<forall>n. f n \<le> f (Suc n))"
nipkow@29879
  1449
unfolding mono_def
nipkow@29879
  1450
by (auto intro:lift_Suc_mono_le[of f])
nipkow@27625
  1451
nipkow@27789
  1452
lemma mono_nat_linear_lb:
nipkow@27789
  1453
  "(!!m n::nat. m<n \<Longrightarrow> f m < f n) \<Longrightarrow> f(m)+k \<le> f(m+k)"
nipkow@27789
  1454
apply(induct_tac k)
nipkow@27789
  1455
 apply simp
nipkow@27789
  1456
apply(erule_tac x="m+n" in meta_allE)
huffman@30079
  1457
apply(erule_tac x="Suc(m+n)" in meta_allE)
nipkow@27789
  1458
apply simp
nipkow@27789
  1459
done
nipkow@27789
  1460
nipkow@27789
  1461
wenzelm@21243
  1462
text{*Subtraction laws, mostly by Clemens Ballarin*}
wenzelm@21243
  1463
wenzelm@21243
  1464
lemma diff_less_mono: "[| a < (b::nat); c \<le> a |] ==> a-c < b-c"
nipkow@24438
  1465
by arith
wenzelm@21243
  1466
wenzelm@21243
  1467
lemma less_diff_conv: "(i < j-k) = (i+k < (j::nat))"
nipkow@24438
  1468
by arith
wenzelm@21243
  1469
wenzelm@21243
  1470
lemma le_diff_conv: "(j-k \<le> (i::nat)) = (j \<le> i+k)"
nipkow@24438
  1471
by arith
wenzelm@21243
  1472
wenzelm@21243
  1473
lemma le_diff_conv2: "k \<le> j ==> (i \<le> j-k) = (i+k \<le> (j::nat))"
nipkow@24438
  1474
by arith
wenzelm@21243
  1475
wenzelm@21243
  1476
lemma diff_diff_cancel [simp]: "i \<le> (n::nat) ==> n - (n - i) = i"
nipkow@24438
  1477
by arith
wenzelm@21243
  1478
wenzelm@21243
  1479
lemma le_add_diff: "k \<le> (n::nat) ==> m \<le> n + m - k"
nipkow@24438
  1480
by arith
wenzelm@21243
  1481
wenzelm@21243
  1482
(*Replaces the previous diff_less and le_diff_less, which had the stronger
wenzelm@21243
  1483
  second premise n\<le>m*)
wenzelm@21243
  1484
lemma diff_less[simp]: "!!m::nat. [| 0<n; 0<m |] ==> m - n < m"
nipkow@24438
  1485
by arith
wenzelm@21243
  1486
haftmann@26072
  1487
text {* Simplification of relational expressions involving subtraction *}
wenzelm@21243
  1488
wenzelm@21243
  1489
lemma diff_diff_eq: "[| k \<le> m;  k \<le> (n::nat) |] ==> ((m-k) - (n-k)) = (m-n)"
nipkow@24438
  1490
by (simp split add: nat_diff_split)
wenzelm@21243
  1491
wenzelm@21243
  1492
lemma eq_diff_iff: "[| k \<le> m;  k \<le> (n::nat) |] ==> (m-k = n-k) = (m=n)"
nipkow@24438
  1493
by (auto split add: nat_diff_split)
wenzelm@21243
  1494
wenzelm@21243
  1495
lemma less_diff_iff: "[| k \<le> m;  k \<le> (n::nat) |] ==> (m-k < n-k) = (m<n)"
nipkow@24438
  1496
by (auto split add: nat_diff_split)
wenzelm@21243
  1497
wenzelm@21243
  1498
lemma le_diff_iff: "[| k \<le> m;  k \<le> (n::nat) |] ==> (m-k \<le> n-k) = (m\<le>n)"
nipkow@24438
  1499
by (auto split add: nat_diff_split)
wenzelm@21243
  1500
wenzelm@21243
  1501
text{*(Anti)Monotonicity of subtraction -- by Stephan Merz*}
wenzelm@21243
  1502
wenzelm@21243
  1503
(* Monotonicity of subtraction in first argument *)
wenzelm@21243
  1504
lemma diff_le_mono: "m \<le> (n::nat) ==> (m-l) \<le> (n-l)"
nipkow@24438
  1505
by (simp split add: nat_diff_split)
wenzelm@21243
  1506
wenzelm@21243
  1507
lemma diff_le_mono2: "m \<le> (n::nat) ==> (l-n) \<le> (l-m)"
nipkow@24438
  1508
by (simp split add: nat_diff_split)
wenzelm@21243
  1509
wenzelm@21243
  1510
lemma diff_less_mono2: "[| m < (n::nat); m<l |] ==> (l-n) < (l-m)"
nipkow@24438
  1511
by (simp split add: nat_diff_split)
wenzelm@21243
  1512
wenzelm@21243
  1513
lemma diffs0_imp_equal: "!!m::nat. [| m-n = 0; n-m = 0 |] ==>  m=n"
nipkow@24438
  1514
by (simp split add: nat_diff_split)
wenzelm@21243
  1515
bulwahn@26143
  1516
lemma min_diff: "min (m - (i::nat)) (n - i) = min m n - i"
nipkow@32437
  1517
by auto
bulwahn@26143
  1518
bulwahn@26143
  1519
lemma inj_on_diff_nat: 
bulwahn@26143
  1520
  assumes k_le_n: "\<forall>n \<in> N. k \<le> (n::nat)"
bulwahn@26143
  1521
  shows "inj_on (\<lambda>n. n - k) N"
bulwahn@26143
  1522
proof (rule inj_onI)
bulwahn@26143
  1523
  fix x y
bulwahn@26143
  1524
  assume a: "x \<in> N" "y \<in> N" "x - k = y - k"
bulwahn@26143
  1525
  with k_le_n have "x - k + k = y - k + k" by auto
bulwahn@26143
  1526
  with a k_le_n show "x = y" by auto
bulwahn@26143
  1527
qed
bulwahn@26143
  1528
haftmann@26072
  1529
text{*Rewriting to pull differences out*}
haftmann@26072
  1530
haftmann@26072
  1531
lemma diff_diff_right [simp]: "k\<le>j --> i - (j - k) = i + (k::nat) - j"
haftmann@26072
  1532
by arith
haftmann@26072
  1533
haftmann@26072
  1534
lemma diff_Suc_diff_eq1 [simp]: "k \<le> j ==> m - Suc (j - k) = m + k - Suc j"
haftmann@26072
  1535
by arith
haftmann@26072
  1536
haftmann@26072
  1537
lemma diff_Suc_diff_eq2 [simp]: "k \<le> j ==> Suc (j - k) - m = Suc j - (k + m)"
haftmann@26072
  1538
by arith
haftmann@26072
  1539
wenzelm@21243
  1540
text{*Lemmas for ex/Factorization*}
wenzelm@21243
  1541
wenzelm@21243
  1542
lemma one_less_mult: "[| Suc 0 < n; Suc 0 < m |] ==> Suc 0 < m*n"
nipkow@24438
  1543
by (cases m) auto
wenzelm@21243
  1544
wenzelm@21243
  1545
lemma n_less_m_mult_n: "[| Suc 0 < n; Suc 0 < m |] ==> n<m*n"
nipkow@24438
  1546
by (cases m) auto
wenzelm@21243
  1547
wenzelm@21243
  1548
lemma n_less_n_mult_m: "[| Suc 0 < n; Suc 0 < m |] ==> n<n*m"
nipkow@24438
  1549
by (cases m) auto
wenzelm@21243
  1550
krauss@23001
  1551
text {* Specialized induction principles that work "backwards": *}
krauss@23001
  1552
krauss@23001
  1553
lemma inc_induct[consumes 1, case_names base step]:
krauss@23001
  1554
  assumes less: "i <= j"
krauss@23001
  1555
  assumes base: "P j"
krauss@23001
  1556
  assumes step: "!!i. [| i < j; P (Suc i) |] ==> P i"
krauss@23001
  1557
  shows "P i"
krauss@23001
  1558
  using less
krauss@23001
  1559
proof (induct d=="j - i" arbitrary: i)
krauss@23001
  1560
  case (0 i)
krauss@23001
  1561
  hence "i = j" by simp
krauss@23001
  1562
  with base show ?case by simp
krauss@23001
  1563
next
krauss@23001
  1564
  case (Suc d i)
krauss@23001
  1565
  hence "i < j" "P (Suc i)"
krauss@23001
  1566
    by simp_all
krauss@23001
  1567
  thus "P i" by (rule step)
krauss@23001
  1568
qed
krauss@23001
  1569
krauss@23001
  1570
lemma strict_inc_induct[consumes 1, case_names base step]:
krauss@23001
  1571
  assumes less: "i < j"
krauss@23001
  1572
  assumes base: "!!i. j = Suc i ==> P i"
krauss@23001
  1573
  assumes step: "!!i. [| i < j; P (Suc i) |] ==> P i"
krauss@23001
  1574
  shows "P i"
krauss@23001
  1575
  using less
krauss@23001
  1576
proof (induct d=="j - i - 1" arbitrary: i)
krauss@23001
  1577
  case (0 i)
krauss@23001
  1578
  with `i < j` have "j = Suc i" by simp
krauss@23001
  1579
  with base show ?case by simp
krauss@23001
  1580
next
krauss@23001
  1581
  case (Suc d i)
krauss@23001
  1582
  hence "i < j" "P (Suc i)"
krauss@23001
  1583
    by simp_all
krauss@23001
  1584
  thus "P i" by (rule step)
krauss@23001
  1585
qed
krauss@23001
  1586
krauss@23001
  1587
lemma zero_induct_lemma: "P k ==> (!!n. P (Suc n) ==> P n) ==> P (k - i)"
krauss@23001
  1588
  using inc_induct[of "k - i" k P, simplified] by blast
krauss@23001
  1589
krauss@23001
  1590
lemma zero_induct: "P k ==> (!!n. P (Suc n) ==> P n) ==> P 0"
krauss@23001
  1591
  using inc_induct[of 0 k P] by blast
wenzelm@21243
  1592
wenzelm@21243
  1593
(*The others are
wenzelm@21243
  1594
      i - j - k = i - (j + k),
wenzelm@21243
  1595
      k \<le> j ==> j - k + i = j + i - k,
wenzelm@21243
  1596
      k \<le> j ==> i + (j - k) = i + j - k *)
wenzelm@21243
  1597
lemmas add_diff_assoc = diff_add_assoc [symmetric]
wenzelm@21243
  1598
lemmas add_diff_assoc2 = diff_add_assoc2[symmetric]
haftmann@26072
  1599
declare diff_diff_left [simp]  add_diff_assoc [simp] add_diff_assoc2[simp]
wenzelm@21243
  1600
wenzelm@21243
  1601
text{*At present we prove no analogue of @{text not_less_Least} or @{text
wenzelm@21243
  1602
Least_Suc}, since there appears to be no need.*}
wenzelm@21243
  1603
nipkow@27625
  1604
haftmann@33274
  1605
subsection {* The divides relation on @{typ nat} *}
haftmann@33274
  1606
haftmann@33274
  1607
lemma dvd_1_left [iff]: "Suc 0 dvd k"
haftmann@33274
  1608
unfolding dvd_def by simp
haftmann@33274
  1609
haftmann@33274
  1610
lemma dvd_1_iff_1 [simp]: "(m dvd Suc 0) = (m = Suc 0)"
haftmann@33274
  1611
by (simp add: dvd_def)
haftmann@33274
  1612
haftmann@33274
  1613
lemma nat_dvd_1_iff_1 [simp]: "m dvd (1::nat) \<longleftrightarrow> m = 1"
haftmann@33274
  1614
by (simp add: dvd_def)
haftmann@33274
  1615
nipkow@33657
  1616
lemma dvd_antisym: "[| m dvd n; n dvd m |] ==> m = (n::nat)"
haftmann@33274
  1617
  unfolding dvd_def
haftmann@33274
  1618
  by (force dest: mult_eq_self_implies_10 simp add: mult_assoc mult_eq_1_iff)
haftmann@33274
  1619
haftmann@33274
  1620
text {* @{term "op dvd"} is a partial order *}
haftmann@33274
  1621
haftmann@33274
  1622
interpretation dvd: order "op dvd" "\<lambda>n m \<Colon> nat. n dvd m \<and> \<not> m dvd n"
nipkow@33657
  1623
  proof qed (auto intro: dvd_refl dvd_trans dvd_antisym)
haftmann@33274
  1624
haftmann@33274
  1625
lemma dvd_diff_nat[simp]: "[| k dvd m; k dvd n |] ==> k dvd (m-n :: nat)"
haftmann@33274
  1626
unfolding dvd_def
haftmann@33274
  1627
by (blast intro: diff_mult_distrib2 [symmetric])
haftmann@33274
  1628
haftmann@33274
  1629
lemma dvd_diffD: "[| k dvd m-n; k dvd n; n\<le>m |] ==> k dvd (m::nat)"
haftmann@33274
  1630
  apply (erule linorder_not_less [THEN iffD2, THEN add_diff_inverse, THEN subst])
haftmann@33274
  1631
  apply (blast intro: dvd_add)
haftmann@33274
  1632
  done
haftmann@33274
  1633
haftmann@33274
  1634
lemma dvd_diffD1: "[| k dvd m-n; k dvd m; n\<le>m |] ==> k dvd (n::nat)"
haftmann@33274
  1635
by (drule_tac m = m in dvd_diff_nat, auto)
haftmann@33274
  1636
haftmann@33274
  1637
lemma dvd_reduce: "(k dvd n + k) = (k dvd (n::nat))"
haftmann@33274
  1638
  apply (rule iffI)
haftmann@33274
  1639
   apply (erule_tac [2] dvd_add)
haftmann@33274
  1640
   apply (rule_tac [2] dvd_refl)
haftmann@33274
  1641
  apply (subgoal_tac "n = (n+k) -k")
haftmann@33274
  1642
   prefer 2 apply simp
haftmann@33274
  1643
  apply (erule ssubst)
haftmann@33274
  1644
  apply (erule dvd_diff_nat)
haftmann@33274
  1645
  apply (rule dvd_refl)
haftmann@33274
  1646
  done
haftmann@33274
  1647
haftmann@33274
  1648
lemma dvd_mult_cancel: "!!k::nat. [| k*m dvd k*n; 0<k |] ==> m dvd n"
haftmann@33274
  1649
  unfolding dvd_def
haftmann@33274
  1650
  apply (erule exE)
haftmann@33274
  1651
  apply (simp add: mult_ac)
haftmann@33274
  1652
  done
haftmann@33274
  1653
haftmann@33274
  1654
lemma dvd_mult_cancel1: "0<m ==> (m*n dvd m) = (n = (1::nat))"
haftmann@33274
  1655
  apply auto
haftmann@33274
  1656
   apply (subgoal_tac "m*n dvd m*1")
haftmann@33274
  1657
   apply (drule dvd_mult_cancel, auto)
haftmann@33274
  1658
  done
haftmann@33274
  1659
haftmann@33274
  1660
lemma dvd_mult_cancel2: "0<m ==> (n*m dvd m) = (n = (1::nat))"
haftmann@33274
  1661
  apply (subst mult_commute)
haftmann@33274
  1662
  apply (erule dvd_mult_cancel1)
haftmann@33274
  1663
  done
haftmann@33274
  1664
haftmann@33274
  1665
lemma dvd_imp_le: "[| k dvd n; 0 < n |] ==> k \<le> (n::nat)"
haftmann@33274
  1666
by (auto elim!: dvdE) (auto simp add: gr0_conv_Suc)
haftmann@33274
  1667
haftmann@33274
  1668
lemma nat_dvd_not_less:
haftmann@33274
  1669
  fixes m n :: nat
haftmann@33274
  1670
  shows "0 < m \<Longrightarrow> m < n \<Longrightarrow> \<not> n dvd m"
haftmann@33274
  1671
by (auto elim!: dvdE) (auto simp add: gr0_conv_Suc)
haftmann@33274
  1672
haftmann@33274
  1673
haftmann@26072
  1674
subsection {* size of a datatype value *}
haftmann@25193
  1675
haftmann@29608
  1676
class size =
krauss@26748
  1677
  fixes size :: "'a \<Rightarrow> nat" -- {* see further theory @{text Wellfounded} *}
haftmann@23852
  1678
haftmann@33364
  1679
haftmann@33364
  1680
subsection {* code module namespace *}
haftmann@33364
  1681
haftmann@33364
  1682
code_modulename SML
haftmann@33364
  1683
  Nat Arith
haftmann@33364
  1684
haftmann@33364
  1685
code_modulename OCaml
haftmann@33364
  1686
  Nat Arith
haftmann@33364
  1687
haftmann@33364
  1688
code_modulename Haskell
haftmann@33364
  1689
  Nat Arith
haftmann@33364
  1690
haftmann@25193
  1691
end