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theory Nat(* Title: HOL/Nat.thy ID: $Id: Nat.thy,v 1.59 2005/09/28 22:58:55 wenzelm Exp $ Author: Tobias Nipkow and Lawrence C Paulson Type "nat" is a linear order, and a datatype; arithmetic operators + - and * (for div, mod and dvd, see theory Divides). *) header {* Natural numbers *} theory Nat imports Wellfounded_Recursion Ring_and_Field begin subsection {* Type @{text ind} *} typedecl ind consts Zero_Rep :: ind Suc_Rep :: "ind => ind" axioms -- {* the axiom of infinity in 2 parts *} inj_Suc_Rep: "inj Suc_Rep" Suc_Rep_not_Zero_Rep: "Suc_Rep x ≠ Zero_Rep" finalconsts Zero_Rep Suc_Rep subsection {* Type nat *} text {* Type definition *} consts Nat :: "ind set" inductive Nat intros Zero_RepI: "Zero_Rep : Nat" Suc_RepI: "i : Nat ==> Suc_Rep i : Nat" global typedef (open Nat) nat = Nat by (rule exI, rule Nat.Zero_RepI) instance nat :: "{ord, zero, one}" .. text {* Abstract constants and syntax *} consts Suc :: "nat => nat" pred_nat :: "(nat * nat) set" local defs Zero_nat_def: "0 == Abs_Nat Zero_Rep" Suc_def: "Suc == (%n. Abs_Nat (Suc_Rep (Rep_Nat n)))" One_nat_def [simp]: "1 == Suc 0" -- {* nat operations *} pred_nat_def: "pred_nat == {(m, n). n = Suc m}" less_def: "m < n == (m, n) : trancl pred_nat" le_def: "m ≤ (n::nat) == ~ (n < m)" text {* Induction *} theorem nat_induct: "P 0 ==> (!!n. P n ==> P (Suc n)) ==> P n" apply (unfold Zero_nat_def Suc_def) apply (rule Rep_Nat_inverse [THEN subst]) -- {* types force good instantiation *} apply (erule Rep_Nat [THEN Nat.induct]) apply (iprover elim: Abs_Nat_inverse [THEN subst]) done text {* Distinctness of constructors *} lemma Suc_not_Zero [iff]: "Suc m ≠ 0" by (simp add: Zero_nat_def Suc_def Abs_Nat_inject Rep_Nat Suc_RepI Zero_RepI Suc_Rep_not_Zero_Rep) lemma Zero_not_Suc [iff]: "0 ≠ Suc m" by (rule not_sym, rule Suc_not_Zero not_sym) lemma Suc_neq_Zero: "Suc m = 0 ==> R" by (rule notE, rule Suc_not_Zero) lemma Zero_neq_Suc: "0 = Suc m ==> R" by (rule Suc_neq_Zero, erule sym) text {* Injectiveness of @{term Suc} *} lemma inj_Suc[simp]: "inj_on Suc N" by (simp add: Suc_def inj_on_def Abs_Nat_inject Rep_Nat Suc_RepI inj_Suc_Rep [THEN inj_eq] Rep_Nat_inject) lemma Suc_inject: "Suc x = Suc y ==> x = y" by (rule inj_Suc [THEN injD]) lemma Suc_Suc_eq [iff]: "(Suc m = Suc n) = (m = n)" by (rule inj_Suc [THEN inj_eq]) lemma nat_not_singleton: "(∀x. x = (0::nat)) = False" by auto text {* @{typ nat} is a datatype *} rep_datatype nat distinct Suc_not_Zero Zero_not_Suc inject Suc_Suc_eq induction nat_induct lemma n_not_Suc_n: "n ≠ Suc n" by (induct n) simp_all lemma Suc_n_not_n: "Suc t ≠ t" by (rule not_sym, rule n_not_Suc_n) text {* A special form of induction for reasoning about @{term "m < n"} and @{term "m - n"} *} theorem diff_induct: "(!!x. P x 0) ==> (!!y. P 0 (Suc y)) ==> (!!x y. P x y ==> P (Suc x) (Suc y)) ==> P m n" apply (rule_tac x = m in spec) apply (induct n) prefer 2 apply (rule allI) apply (induct_tac x, iprover+) done subsection {* Basic properties of "less than" *} lemma wf_pred_nat: "wf pred_nat" apply (unfold wf_def pred_nat_def, clarify) apply (induct_tac x, blast+) done lemma wf_less: "wf {(x, y::nat). x < y}" apply (unfold less_def) apply (rule wf_pred_nat [THEN wf_trancl, THEN wf_subset], blast) done lemma less_eq: "((m, n) : pred_nat^+) = (m < n)" apply (unfold less_def) apply (rule refl) done subsubsection {* Introduction properties *} lemma less_trans: "i < j ==> j < k ==> i < (k::nat)" apply (unfold less_def) apply (rule trans_trancl [THEN transD], assumption+) done lemma lessI [iff]: "n < Suc n" apply (unfold less_def pred_nat_def) apply (simp add: r_into_trancl) done lemma less_SucI: "i < j ==> i < Suc j" apply (rule less_trans, assumption) apply (rule lessI) done lemma zero_less_Suc [iff]: "0 < Suc n" apply (induct n) apply (rule lessI) apply (erule less_trans) apply (rule lessI) done subsubsection {* Elimination properties *} lemma less_not_sym: "n < m ==> ~ m < (n::nat)" apply (unfold less_def) apply (blast intro: wf_pred_nat wf_trancl [THEN wf_asym]) done lemma less_asym: assumes h1: "(n::nat) < m" and h2: "~ P ==> m < n" shows P apply (rule contrapos_np) apply (rule less_not_sym) apply (rule h1) apply (erule h2) done lemma less_not_refl: "~ n < (n::nat)" apply (unfold less_def) apply (rule wf_pred_nat [THEN wf_trancl, THEN wf_not_refl]) done lemma less_irrefl [elim!]: "(n::nat) < n ==> R" by (rule notE, rule less_not_refl) lemma less_not_refl2: "n < m ==> m ≠ (n::nat)" by blast lemma less_not_refl3: "(s::nat) < t ==> s ≠ t" by (rule not_sym, rule less_not_refl2) lemma lessE: assumes major: "i < k" and p1: "k = Suc i ==> P" and p2: "!!j. i < j ==> k = Suc j ==> P" shows P apply (rule major [unfolded less_def pred_nat_def, THEN tranclE], simp_all) apply (erule p1) apply (rule p2) apply (simp add: less_def pred_nat_def, assumption) done lemma not_less0 [iff]: "~ n < (0::nat)" by (blast elim: lessE) lemma less_zeroE: "(n::nat) < 0 ==> R" by (rule notE, rule not_less0) lemma less_SucE: assumes major: "m < Suc n" and less: "m < n ==> P" and eq: "m = n ==> P" shows P apply (rule major [THEN lessE]) apply (rule eq, blast) apply (rule less, blast) done lemma less_Suc_eq: "(m < Suc n) = (m < n | m = n)" by (blast elim!: less_SucE intro: less_trans) lemma less_one [iff]: "(n < (1::nat)) = (n = 0)" by (simp add: less_Suc_eq) lemma less_Suc0 [iff]: "(n < Suc 0) = (n = 0)" by (simp add: less_Suc_eq) lemma Suc_mono: "m < n ==> Suc m < Suc n" by (induct n) (fast elim: less_trans lessE)+ text {* "Less than" is a linear ordering *} lemma less_linear: "m < n | m = n | n < (m::nat)" apply (induct m) apply (induct n) apply (rule refl [THEN disjI1, THEN disjI2]) apply (rule zero_less_Suc [THEN disjI1]) apply (blast intro: Suc_mono less_SucI elim: lessE) done text {* "Less than" is antisymmetric, sort of *} lemma less_antisym: "[| ¬ n < m; n < Suc m |] ==> m = n" apply(simp only:less_Suc_eq) apply blast done lemma nat_neq_iff: "((m::nat) ≠ n) = (m < n | n < m)" using less_linear by blast lemma nat_less_cases: assumes major: "(m::nat) < n ==> P n m" and eqCase: "m = n ==> P n m" and lessCase: "n<m ==> P n m" shows "P n m" apply (rule less_linear [THEN disjE]) apply (erule_tac [2] disjE) apply (erule lessCase) apply (erule sym [THEN eqCase]) apply (erule major) done subsubsection {* Inductive (?) properties *} lemma Suc_lessI: "m < n ==> Suc m ≠ n ==> Suc m < n" apply (simp add: nat_neq_iff) apply (blast elim!: less_irrefl less_SucE elim: less_asym) done lemma Suc_lessD: "Suc m < n ==> m < n" apply (induct n) apply (fast intro!: lessI [THEN less_SucI] elim: less_trans lessE)+ done lemma Suc_lessE: assumes major: "Suc i < k" and minor: "!!j. i < j ==> k = Suc j ==> P" shows P apply (rule major [THEN lessE]) apply (erule lessI [THEN minor]) apply (erule Suc_lessD [THEN minor], assumption) done lemma Suc_less_SucD: "Suc m < Suc n ==> m < n" by (blast elim: lessE dest: Suc_lessD) lemma Suc_less_eq [iff, code]: "(Suc m < Suc n) = (m < n)" apply (rule iffI) apply (erule Suc_less_SucD) apply (erule Suc_mono) done lemma less_trans_Suc: assumes le: "i < j" shows "j < k ==> Suc i < k" apply (induct k, simp_all) apply (insert le) apply (simp add: less_Suc_eq) apply (blast dest: Suc_lessD) done lemma [code]: "((n::nat) < 0) = False" by simp lemma [code]: "(0 < Suc n) = True" by simp text {* Can be used with @{text less_Suc_eq} to get @{term "n = m | n < m"} *} lemma not_less_eq: "(~ m < n) = (n < Suc m)" by (rule_tac m = m and n = n in diff_induct, simp_all) text {* Complete induction, aka course-of-values induction *} lemma nat_less_induct: assumes prem: "!!n. ∀m::nat. m < n --> P m ==> P n" shows "P n" apply (rule_tac a=n in wf_induct) apply (rule wf_pred_nat [THEN wf_trancl]) apply (rule prem) apply (unfold less_def, assumption) done lemmas less_induct = nat_less_induct [rule_format, case_names less] subsection {* Properties of "less than or equal" *} text {* Was @{text le_eq_less_Suc}, but this orientation is more useful *} lemma less_Suc_eq_le: "(m < Suc n) = (m ≤ n)" by (unfold le_def, rule not_less_eq [symmetric]) lemma le_imp_less_Suc: "m ≤ n ==> m < Suc n" by (rule less_Suc_eq_le [THEN iffD2]) lemma le0 [iff]: "(0::nat) ≤ n" by (unfold le_def, rule not_less0) lemma Suc_n_not_le_n: "~ Suc n ≤ n" by (simp add: le_def) lemma le_0_eq [iff]: "((i::nat) ≤ 0) = (i = 0)" by (induct i) (simp_all add: le_def) lemma le_Suc_eq: "(m ≤ Suc n) = (m ≤ n | m = Suc n)" by (simp del: less_Suc_eq_le add: less_Suc_eq_le [symmetric] less_Suc_eq) lemma le_SucE: "m ≤ Suc n ==> (m ≤ n ==> R) ==> (m = Suc n ==> R) ==> R" by (drule le_Suc_eq [THEN iffD1], iprover+) lemma Suc_leI: "m < n ==> Suc(m) ≤ n" apply (simp add: le_def less_Suc_eq) apply (blast elim!: less_irrefl less_asym) done -- {* formerly called lessD *} lemma Suc_leD: "Suc(m) ≤ n ==> m ≤ n" by (simp add: le_def less_Suc_eq) text {* Stronger version of @{text Suc_leD} *} lemma Suc_le_lessD: "Suc m ≤ n ==> m < n" apply (simp add: le_def less_Suc_eq) using less_linear apply blast done lemma Suc_le_eq: "(Suc m ≤ n) = (m < n)" by (blast intro: Suc_leI Suc_le_lessD) lemma le_SucI: "m ≤ n ==> m ≤ Suc n" by (unfold le_def) (blast dest: Suc_lessD) lemma less_imp_le: "m < n ==> m ≤ (n::nat)" by (unfold le_def) (blast elim: less_asym) text {* For instance, @{text "(Suc m < Suc n) = (Suc m ≤ n) = (m < n)"} *} lemmas le_simps = less_imp_le less_Suc_eq_le Suc_le_eq text {* Equivalence of @{term "m ≤ n"} and @{term "m < n | m = n"} *} lemma le_imp_less_or_eq: "m ≤ n ==> m < n | m = (n::nat)" apply (unfold le_def) using less_linear apply (blast elim: less_irrefl less_asym) done lemma less_or_eq_imp_le: "m < n | m = n ==> m ≤ (n::nat)" apply (unfold le_def) using less_linear apply (blast elim!: less_irrefl elim: less_asym) done lemma le_eq_less_or_eq: "(m ≤ (n::nat)) = (m < n | m=n)" by (iprover intro: less_or_eq_imp_le le_imp_less_or_eq) text {* Useful with @{text Blast}. *} lemma eq_imp_le: "(m::nat) = n ==> m ≤ n" by (rule less_or_eq_imp_le, rule disjI2) lemma le_refl: "n ≤ (n::nat)" by (simp add: le_eq_less_or_eq) lemma le_less_trans: "[| i ≤ j; j < k |] ==> i < (k::nat)" by (blast dest!: le_imp_less_or_eq intro: less_trans) lemma less_le_trans: "[| i < j; j ≤ k |] ==> i < (k::nat)" by (blast dest!: le_imp_less_or_eq intro: less_trans) lemma le_trans: "[| i ≤ j; j ≤ k |] ==> i ≤ (k::nat)" by (blast dest!: le_imp_less_or_eq intro: less_or_eq_imp_le less_trans) lemma le_anti_sym: "[| m ≤ n; n ≤ m |] ==> m = (n::nat)" by (blast dest!: le_imp_less_or_eq elim!: less_irrefl elim: less_asym) lemma Suc_le_mono [iff]: "(Suc n ≤ Suc m) = (n ≤ m)" by (simp add: le_simps) text {* Axiom @{text order_less_le} of class @{text order}: *} lemma nat_less_le: "((m::nat) < n) = (m ≤ n & m ≠ n)" by (simp add: le_def nat_neq_iff) (blast elim!: less_asym) lemma le_neq_implies_less: "(m::nat) ≤ n ==> m ≠ n ==> m < n" by (rule iffD2, rule nat_less_le, rule conjI) text {* Axiom @{text linorder_linear} of class @{text linorder}: *} lemma nat_le_linear: "(m::nat) ≤ n | n ≤ m" apply (simp add: le_eq_less_or_eq) using less_linear apply blast done text {* Type {@typ nat} is a wellfounded linear order *} instance nat :: "{order, linorder, wellorder}" by intro_classes (assumption | rule le_refl le_trans le_anti_sym nat_less_le nat_le_linear wf_less)+ lemmas linorder_neqE_nat = linorder_neqE[where 'a = nat] lemma not_less_less_Suc_eq: "~ n < m ==> (n < Suc m) = (n = m)" by (blast elim!: less_SucE) text {* Rewrite @{term "n < Suc m"} to @{term "n = m"} if @{term "~ n < m"} or @{term "m ≤ n"} hold. Not suitable as default simprules because they often lead to looping *} lemma le_less_Suc_eq: "m ≤ n ==> (n < Suc m) = (n = m)" by (rule not_less_less_Suc_eq, rule leD) lemmas not_less_simps = not_less_less_Suc_eq le_less_Suc_eq text {* Re-orientation of the equations @{text "0 = x"} and @{text "1 = x"}. No longer added as simprules (they loop) but via @{text reorient_simproc} in Bin *} text {* Polymorphic, not just for @{typ nat} *} lemma zero_reorient: "(0 = x) = (x = 0)" by auto lemma one_reorient: "(1 = x) = (x = 1)" by auto subsection {* Arithmetic operators *} axclass power < type consts power :: "('a::power) => nat => 'a" (infixr "^" 80) text {* arithmetic operators @{text "+ -"} and @{text "*"} *} instance nat :: "{plus, minus, times, power}" .. text {* size of a datatype value; overloaded *} consts size :: "'a => nat" primrec add_0: "0 + n = n" add_Suc: "Suc m + n = Suc (m + n)" primrec diff_0: "m - 0 = m" diff_Suc: "m - Suc n = (case m - n of 0 => 0 | Suc k => k)" primrec mult_0: "0 * n = 0" mult_Suc: "Suc m * n = n + (m * n)" text {* These two rules ease the use of primitive recursion. NOTE USE OF @{text "=="} *} lemma def_nat_rec_0: "(!!n. f n == nat_rec c h n) ==> f 0 = c" by simp lemma def_nat_rec_Suc: "(!!n. f n == nat_rec c h n) ==> f (Suc n) = h n (f n)" by simp lemma not0_implies_Suc: "n ≠ 0 ==> ∃m. n = Suc m" by (case_tac n) simp_all lemma gr_implies_not0: "!!n::nat. m<n ==> n ≠ 0" by (case_tac n) simp_all lemma neq0_conv [iff]: "!!n::nat. (n ≠ 0) = (0 < n)" by (case_tac n) simp_all text {* This theorem is useful with @{text blast} *} lemma gr0I: "((n::nat) = 0 ==> False) ==> 0 < n" by (rule iffD1, rule neq0_conv, iprover) lemma gr0_conv_Suc: "(0 < n) = (∃m. n = Suc m)" by (fast intro: not0_implies_Suc) lemma not_gr0 [iff]: "!!n::nat. (~ (0 < n)) = (n = 0)" apply (rule iffI) apply (rule ccontr, simp_all) done lemma Suc_le_D: "(Suc n ≤ m') ==> (? m. m' = Suc m)" by (induct m') simp_all text {* Useful in certain inductive arguments *} lemma less_Suc_eq_0_disj: "(m < Suc n) = (m = 0 | (∃j. m = Suc j & j < n))" by (case_tac m) simp_all lemma nat_induct2: "[|P 0; P (Suc 0); !!k. P k ==> P (Suc (Suc k))|] ==> P n" apply (rule nat_less_induct) apply (case_tac n) apply (case_tac [2] nat) apply (blast intro: less_trans)+ done subsection {* @{text LEAST} theorems for type @{typ nat}*} lemma Least_Suc: "[| P n; ~ P 0 |] ==> (LEAST n. P n) = Suc (LEAST m. P(Suc m))" apply (case_tac "n", auto) apply (frule LeastI) apply (drule_tac P = "%x. P (Suc x) " in LeastI) apply (subgoal_tac " (LEAST x. P x) ≤ Suc (LEAST x. P (Suc x))") apply (erule_tac [2] Least_le) apply (case_tac "LEAST x. P x", auto) apply (drule_tac P = "%x. P (Suc x) " in Least_le) apply (blast intro: order_antisym) done lemma Least_Suc2: "[|P n; Q m; ~P 0; !k. P (Suc k) = Q k|] ==> Least P = Suc (Least Q)" by (erule (1) Least_Suc [THEN ssubst], simp) subsection {* @{term min} and @{term max} *} lemma min_0L [simp]: "min 0 n = (0::nat)" by (rule min_leastL) simp lemma min_0R [simp]: "min n 0 = (0::nat)" by (rule min_leastR) simp lemma min_Suc_Suc [simp]: "min (Suc m) (Suc n) = Suc (min m n)" by (simp add: min_of_mono) lemma max_0L [simp]: "max 0 n = (n::nat)" by (rule max_leastL) simp lemma max_0R [simp]: "max n 0 = (n::nat)" by (rule max_leastR) simp lemma max_Suc_Suc [simp]: "max (Suc m) (Suc n) = Suc(max m n)" by (simp add: max_of_mono) subsection {* Basic rewrite rules for the arithmetic operators *} text {* Difference *} lemma diff_0_eq_0 [simp, code]: "0 - n = (0::nat)" by (induct n) simp_all lemma diff_Suc_Suc [simp, code]: "Suc(m) - Suc(n) = m - n" by (induct n) simp_all text {* Could be (and is, below) generalized in various ways However, none of the generalizations are currently in the simpset, and I dread to think what happens if I put them in *} lemma Suc_pred [simp]: "0 < n ==> Suc (n - Suc 0) = n" by (simp split add: nat.split) declare diff_Suc [simp del, code del] subsection {* Addition *} lemma add_0_right [simp]: "m + 0 = (m::nat)" by (induct m) simp_all lemma add_Suc_right [simp]: "m + Suc n = Suc (m + n)" by (induct m) simp_all lemma [code]: "Suc m + n = m + Suc n" by simp text {* Associative law for addition *} lemma nat_add_assoc: "(m + n) + k = m + ((n + k)::nat)" by (induct m) simp_all text {* Commutative law for addition *} lemma nat_add_commute: "m + n = n + (m::nat)" by (induct m) simp_all lemma nat_add_left_commute: "x + (y + z) = y + ((x + z)::nat)" apply (rule mk_left_commute [of "op +"]) apply (rule nat_add_assoc) apply (rule nat_add_commute) done lemma nat_add_left_cancel [simp]: "(k + m = k + n) = (m = (n::nat))" by (induct k) simp_all lemma nat_add_right_cancel [simp]: "(m + k = n + k) = (m=(n::nat))" by (induct k) simp_all lemma nat_add_left_cancel_le [simp]: "(k + m ≤ k + n) = (m≤(n::nat))" by (induct k) simp_all lemma nat_add_left_cancel_less [simp]: "(k + m < k + n) = (m<(n::nat))" by (induct k) simp_all text {* Reasoning about @{text "m + 0 = 0"}, etc. *} lemma add_is_0 [iff]: "!!m::nat. (m + n = 0) = (m = 0 & n = 0)" by (case_tac m) simp_all lemma add_is_1: "(m+n= Suc 0) = (m= Suc 0 & n=0 | m=0 & n= Suc 0)" by (case_tac m) simp_all lemma one_is_add: "(Suc 0 = m + n) = (m = Suc 0 & n = 0 | m = 0 & n = Suc 0)" by (rule trans, rule eq_commute, rule add_is_1) lemma add_gr_0 [iff]: "!!m::nat. (0 < m + n) = (0 < m | 0 < n)" by (simp del: neq0_conv add: neq0_conv [symmetric]) lemma add_eq_self_zero: "!!m::nat. m + n = m ==> n = 0" apply (drule add_0_right [THEN ssubst]) apply (simp add: nat_add_assoc del: add_0_right) done lemma inj_on_add_nat[simp]: "inj_on (%n::nat. n+k) N" apply(induct k) apply simp apply(drule comp_inj_on[OF _ inj_Suc]) apply (simp add:o_def) done subsection {* Multiplication *} text {* right annihilation in product *} lemma mult_0_right [simp]: "(m::nat) * 0 = 0" by (induct m) simp_all text {* right successor law for multiplication *} lemma mult_Suc_right [simp]: "m * Suc n = m + (m * n)" by (induct m) (simp_all add: nat_add_left_commute) text {* Commutative law for multiplication *} lemma nat_mult_commute: "m * n = n * (m::nat)" by (induct m) simp_all text {* addition distributes over multiplication *} lemma add_mult_distrib: "(m + n) * k = (m * k) + ((n * k)::nat)" by (induct m) (simp_all add: nat_add_assoc nat_add_left_commute) lemma add_mult_distrib2: "k * (m + n) = (k * m) + ((k * n)::nat)" by (induct m) (simp_all add: nat_add_assoc) text {* Associative law for multiplication *} lemma nat_mult_assoc: "(m * n) * k = m * ((n * k)::nat)" by (induct m) (simp_all add: add_mult_distrib) text{*The naturals form a @{text comm_semiring_1_cancel}*} instance nat :: comm_semiring_1_cancel proof fix i j k :: nat show "(i + j) + k = i + (j + k)" by (rule nat_add_assoc) show "i + j = j + i" by (rule nat_add_commute) show "0 + i = i" by simp show "(i * j) * k = i * (j * k)" by (rule nat_mult_assoc) show "i * j = j * i" by (rule nat_mult_commute) show "1 * i = i" by simp show "(i + j) * k = i * k + j * k" by (simp add: add_mult_distrib) show "0 ≠ (1::nat)" by simp assume "k+i = k+j" thus "i=j" by simp qed lemma mult_is_0 [simp]: "((m::nat) * n = 0) = (m=0 | n=0)" apply (induct m) apply (induct_tac [2] n, simp_all) done subsection {* Monotonicity of Addition *} text {* strict, in 1st argument *} lemma add_less_mono1: "i < j ==> i + k < j + (k::nat)" by (induct k) simp_all text {* strict, in both arguments *} lemma add_less_mono: "[|i < j; k < l|] ==> i + k < j + (l::nat)" apply (rule add_less_mono1 [THEN less_trans], assumption+) apply (induct j, simp_all) done text {* Deleted @{text less_natE}; use @{text "less_imp_Suc_add RS exE"} *} lemma less_imp_Suc_add: "m < n ==> (∃k. n = Suc (m + k))" apply (induct n) apply (simp_all add: order_le_less) apply (blast elim!: less_SucE intro!: add_0_right [symmetric] add_Suc_right [symmetric]) done text {* strict, in 1st argument; proof is by induction on @{text "k > 0"} *} lemma mult_less_mono2: "(i::nat) < j ==> 0 < k ==> k * i < k * j" apply (erule_tac m1 = 0 in less_imp_Suc_add [THEN exE], simp) apply (induct_tac x) apply (simp_all add: add_less_mono) done text{*The naturals form an ordered @{text comm_semiring_1_cancel}*} instance nat :: ordered_semidom proof fix i j k :: nat show "0 < (1::nat)" by simp show "i ≤ j ==> k + i ≤ k + j" by simp show "i < j ==> 0 < k ==> k * i < k * j" by (simp add: mult_less_mono2) qed lemma nat_mult_1: "(1::nat) * n = n" by simp lemma nat_mult_1_right: "n * (1::nat) = n" by simp subsection {* Additional theorems about "less than" *} text {* A [clumsy] way of lifting @{text "<"} monotonicity to @{text "≤"} monotonicity *} lemma less_mono_imp_le_mono: assumes lt_mono: "!!i j::nat. i < j ==> f i < f j" and le: "i ≤ j" shows "f i ≤ ((f j)::nat)" using le apply (simp add: order_le_less) apply (blast intro!: lt_mono) done text {* non-strict, in 1st argument *} lemma add_le_mono1: "i ≤ j ==> i + k ≤ j + (k::nat)" by (rule add_right_mono) text {* non-strict, in both arguments *} lemma add_le_mono: "[| i ≤ j; k ≤ l |] ==> i + k ≤ j + (l::nat)" by (rule add_mono) lemma le_add2: "n ≤ ((m + n)::nat)" by (insert add_right_mono [of 0 m n], simp) lemma le_add1: "n ≤ ((n + m)::nat)" by (simp add: add_commute, rule le_add2) lemma less_add_Suc1: "i < Suc (i + m)" by (rule le_less_trans, rule le_add1, rule lessI) lemma less_add_Suc2: "i < Suc (m + i)" by (rule le_less_trans, rule le_add2, rule lessI) lemma less_iff_Suc_add: "(m < n) = (∃k. n = Suc (m + k))" by (iprover intro!: less_add_Suc1 less_imp_Suc_add) lemma trans_le_add1: "(i::nat) ≤ j ==> i ≤ j + m" by (rule le_trans, assumption, rule le_add1) lemma trans_le_add2: "(i::nat) ≤ j ==> i ≤ m + j" by (rule le_trans, assumption, rule le_add2) lemma trans_less_add1: "(i::nat) < j ==> i < j + m" by (rule less_le_trans, assumption, rule le_add1) lemma trans_less_add2: "(i::nat) < j ==> i < m + j" by (rule less_le_trans, assumption, rule le_add2) lemma add_lessD1: "i + j < (k::nat) ==> i < k" apply (rule le_less_trans [of _ "i+j"]) apply (simp_all add: le_add1) done lemma not_add_less1 [iff]: "~ (i + j < (i::nat))" apply (rule notI) apply (erule add_lessD1 [THEN less_irrefl]) done lemma not_add_less2 [iff]: "~ (j + i < (i::nat))" by (simp add: add_commute not_add_less1) lemma add_leD1: "m + k ≤ n ==> m ≤ (n::nat)" apply (rule order_trans [of _ "m+k"]) apply (simp_all add: le_add1) done lemma add_leD2: "m + k ≤ n ==> k ≤ (n::nat)" apply (simp add: add_commute) apply (erule add_leD1) done lemma add_leE: "(m::nat) + k ≤ n ==> (m ≤ n ==> k ≤ n ==> R) ==> R" by (blast dest: add_leD1 add_leD2) text {* needs @{text "!!k"} for @{text add_ac} to work *} lemma less_add_eq_less: "!!k::nat. k < l ==> m + l = k + n ==> m < n" by (force simp del: add_Suc_right simp add: less_iff_Suc_add add_Suc_right [symmetric] add_ac) subsection {* Difference *} lemma diff_self_eq_0 [simp]: "(m::nat) - m = 0" by (induct m) simp_all text {* Addition is the inverse of subtraction: if @{term "n ≤ m"} then @{term "n + (m - n) = m"}. *} lemma add_diff_inverse: "~ m < n ==> n + (m - n) = (m::nat)" by (induct m n rule: diff_induct) simp_all lemma le_add_diff_inverse [simp]: "n ≤ m ==> n + (m - n) = (m::nat)" by (simp add: add_diff_inverse linorder_not_less) lemma le_add_diff_inverse2 [simp]: "n ≤ m ==> (m - n) + n = (m::nat)" by (simp add: le_add_diff_inverse add_commute) subsection {* More results about difference *} lemma Suc_diff_le: "n ≤ m ==> Suc m - n = Suc (m - n)" by (induct m n rule: diff_induct) simp_all lemma diff_less_Suc: "m - n < Suc m" apply (induct m n rule: diff_induct) apply (erule_tac [3] less_SucE) apply (simp_all add: less_Suc_eq) done lemma diff_le_self [simp]: "m - n ≤ (m::nat)" by (induct m n rule: diff_induct) (simp_all add: le_SucI) lemma less_imp_diff_less: "(j::nat) < k ==> j - n < k" by (rule le_less_trans, rule diff_le_self) lemma diff_diff_left: "(i::nat) - j - k = i - (j + k)" by (induct i j rule: diff_induct) simp_all lemma Suc_diff_diff [simp]: "(Suc m - n) - Suc k = m - n - k" by (simp add: diff_diff_left) lemma diff_Suc_less [simp]: "0<n ==> n - Suc i < n" apply (case_tac "n", safe) apply (simp add: le_simps) done text {* This and the next few suggested by Florian Kammueller *} lemma diff_commute: "(i::nat) - j - k = i - k - j" by (simp add: diff_diff_left add_commute) lemma diff_add_assoc: "k ≤ (j::nat) ==> (i + j) - k = i + (j - k)" by (induct j k rule: diff_induct) simp_all lemma diff_add_assoc2: "k ≤ (j::nat) ==> (j + i) - k = (j - k) + i" by (simp add: add_commute diff_add_assoc) lemma diff_add_inverse: "(n + m) - n = (m::nat)" by (induct n) simp_all lemma diff_add_inverse2: "(m + n) - n = (m::nat)" by (simp add: diff_add_assoc) lemma le_imp_diff_is_add: "i ≤ (j::nat) ==> (j - i = k) = (j = k + i)" apply safe apply (simp_all add: diff_add_inverse2) done lemma diff_is_0_eq [simp]: "((m::nat) - n = 0) = (m ≤ n)" by (induct m n rule: diff_induct) simp_all lemma diff_is_0_eq' [simp]: "m ≤ n ==> (m::nat) - n = 0" by (rule iffD2, rule diff_is_0_eq) lemma zero_less_diff [simp]: "(0 < n - (m::nat)) = (m < n)" by (induct m n rule: diff_induct) simp_all lemma less_imp_add_positive: "i < j ==> ∃k::nat. 0 < k & i + k = j" apply (rule_tac x = "j - i" in exI) apply (simp (no_asm_simp) add: add_diff_inverse less_not_sym) done lemma zero_induct_lemma: "P k ==> (!!n. P (Suc n) ==> P n) ==> P (k - i)" apply (induct k i rule: diff_induct) apply (simp_all (no_asm)) apply iprover done lemma zero_induct: "P k ==> (!!n. P (Suc n) ==> P n) ==> P 0" apply (rule diff_self_eq_0 [THEN subst]) apply (rule zero_induct_lemma, iprover+) done lemma diff_cancel: "(k + m) - (k + n) = m - (n::nat)" by (induct k) simp_all lemma diff_cancel2: "(m + k) - (n + k) = m - (n::nat)" by (simp add: diff_cancel add_commute) lemma diff_add_0: "n - (n + m) = (0::nat)" by (induct n) simp_all text {* Difference distributes over multiplication *} lemma diff_mult_distrib: "((m::nat) - n) * k = (m * k) - (n * k)" by (induct m n rule: diff_induct) (simp_all add: diff_cancel) lemma diff_mult_distrib2: "k * ((m::nat) - n) = (k * m) - (k * n)" by (simp add: diff_mult_distrib mult_commute [of k]) -- {* NOT added as rewrites, since sometimes they are used from right-to-left *} lemmas nat_distrib = add_mult_distrib add_mult_distrib2 diff_mult_distrib diff_mult_distrib2 subsection {* Monotonicity of Multiplication *} lemma mult_le_mono1: "i ≤ (j::nat) ==> i * k ≤ j * k" by (simp add: mult_right_mono) lemma mult_le_mono2: "i ≤ (j::nat) ==> k * i ≤ k * j" by (simp add: mult_left_mono) text {* @{text "≤"} monotonicity, BOTH arguments *} lemma mult_le_mono: "i ≤ (j::nat) ==> k ≤ l ==> i * k ≤ j * l" by (simp add: mult_mono) lemma mult_less_mono1: "(i::nat) < j ==> 0 < k ==> i * k < j * k" by (simp add: mult_strict_right_mono) text{*Differs from the standard @{text zero_less_mult_iff} in that there are no negative numbers.*} lemma nat_0_less_mult_iff [simp]: "(0 < (m::nat) * n) = (0 < m & 0 < n)" apply (induct m) apply (case_tac [2] n, simp_all) done lemma one_le_mult_iff [simp]: "(Suc 0 ≤ m * n) = (1 ≤ m & 1 ≤ n)" apply (induct m) apply (case_tac [2] n, simp_all) done lemma mult_eq_1_iff [simp]: "(m * n = Suc 0) = (m = 1 & n = 1)" apply (induct m, simp) apply (induct n, simp, fastsimp) done lemma one_eq_mult_iff [simp]: "(Suc 0 = m * n) = (m = 1 & n = 1)" apply (rule trans) apply (rule_tac [2] mult_eq_1_iff, fastsimp) done lemma mult_less_cancel2 [simp]: "((m::nat) * k < n * k) = (0 < k & m < n)" apply (safe intro!: mult_less_mono1) apply (case_tac k, auto) apply (simp del: le_0_eq add: linorder_not_le [symmetric]) apply (blast intro: mult_le_mono1) done lemma mult_less_cancel1 [simp]: "(k * (m::nat) < k * n) = (0 < k & m < n)" by (simp add: mult_commute [of k]) lemma mult_le_cancel1 [simp]: "(k * (m::nat) ≤ k * n) = (0 < k --> m ≤ n)" by (simp add: linorder_not_less [symmetric], auto) lemma mult_le_cancel2 [simp]: "((m::nat) * k ≤ n * k) = (0 < k --> m ≤ n)" by (simp add: linorder_not_less [symmetric], auto) lemma mult_cancel2 [simp]: "(m * k = n * k) = (m = n | (k = (0::nat)))" apply (cut_tac less_linear, safe, auto) apply (drule mult_less_mono1, assumption, simp)+ done lemma mult_cancel1 [simp]: "(k * m = k * n) = (m = n | (k = (0::nat)))" by (simp add: mult_commute [of k]) lemma Suc_mult_less_cancel1: "(Suc k * m < Suc k * n) = (m < n)" by (subst mult_less_cancel1) simp lemma Suc_mult_le_cancel1: "(Suc k * m ≤ Suc k * n) = (m ≤ n)" by (subst mult_le_cancel1) simp lemma Suc_mult_cancel1: "(Suc k * m = Suc k * n) = (m = n)" by (subst mult_cancel1) simp text {* Lemma for @{text gcd} *} lemma mult_eq_self_implies_10: "(m::nat) = m * n ==> n = 1 | m = 0" apply (drule sym) apply (rule disjCI) apply (rule nat_less_cases, erule_tac [2] _) apply (fastsimp elim!: less_SucE) apply (fastsimp dest: mult_less_mono2) done end
theorem nat_induct:
[| P 0; !!n. P n ==> P (Suc n) |] ==> P n
lemma Suc_not_Zero:
Suc m ≠ 0
lemma Zero_not_Suc:
0 ≠ Suc m
lemma Suc_neq_Zero:
Suc m = 0 ==> R
lemma Zero_neq_Suc:
0 = Suc m ==> R
lemma inj_Suc:
inj_on Suc N
lemma Suc_inject:
Suc x = Suc y ==> x = y
lemma Suc_Suc_eq:
(Suc m = Suc n) = (m = n)
lemma nat_not_singleton:
(∀x. x = 0) = False
lemma n_not_Suc_n:
n ≠ Suc n
lemma Suc_n_not_n:
Suc t ≠ t
theorem diff_induct:
[| !!x. P x 0; !!y. P 0 (Suc y); !!x y. P x y ==> P (Suc x) (Suc y) |] ==> P m n
lemma wf_pred_nat:
wf pred_nat
lemma wf_less:
wf {(x, y). x < y}
lemma less_eq:
((m, n) ∈ pred_nat+) = (m < n)
lemma less_trans:
[| i < j; j < k |] ==> i < k
lemma lessI:
n < Suc n
lemma less_SucI:
i < j ==> i < Suc j
lemma zero_less_Suc:
0 < Suc n
lemma less_not_sym:
n < m ==> ¬ m < n
lemma less_asym:
[| n < m; ¬ P ==> m < n |] ==> P
lemma less_not_refl:
¬ n < n
lemma less_irrefl:
n < n ==> R
lemma less_not_refl2:
n < m ==> m ≠ n
lemma less_not_refl3:
s < t ==> s ≠ t
lemma lessE:
[| i < k; k = Suc i ==> P; !!j. [| i < j; k = Suc j |] ==> P |] ==> P
lemma not_less0:
¬ n < 0
lemma less_zeroE:
n < 0 ==> R
lemma less_SucE:
[| m < Suc n; m < n ==> P; m = n ==> P |] ==> P
lemma less_Suc_eq:
(m < Suc n) = (m < n ∨ m = n)
lemma less_one:
(n < 1) = (n = 0)
lemma less_Suc0:
(n < Suc 0) = (n = 0)
lemma Suc_mono:
m < n ==> Suc m < Suc n
lemma less_linear:
m < n ∨ m = n ∨ n < m
lemma less_antisym:
[| ¬ n < m; n < Suc m |] ==> m = n
lemma nat_neq_iff:
(m ≠ n) = (m < n ∨ n < m)
lemma nat_less_cases:
[| m < n ==> P n m; m = n ==> P n m; n < m ==> P n m |] ==> P n m
lemma Suc_lessI:
[| m < n; Suc m ≠ n |] ==> Suc m < n
lemma Suc_lessD:
Suc m < n ==> m < n
lemma Suc_lessE:
[| Suc i < k; !!j. [| i < j; k = Suc j |] ==> P |] ==> P
lemma Suc_less_SucD:
Suc m < Suc n ==> m < n
lemma Suc_less_eq:
(Suc m < Suc n) = (m < n)
lemma less_trans_Suc:
[| i < j; j < k |] ==> Suc i < k
lemma
(n < 0) = False
lemma
(0 < Suc n) = True
lemma not_less_eq:
(¬ m < n) = (n < Suc m)
lemma nat_less_induct:
(!!n. ∀m<n. P m ==> P n) ==> P n
lemmas less_induct:
(!!n. (!!m. m < n ==> P m) ==> P n) ==> P n
lemmas less_induct:
(!!n. (!!m. m < n ==> P m) ==> P n) ==> P n
lemma less_Suc_eq_le:
(m < Suc n) = (m ≤ n)
lemma le_imp_less_Suc:
m ≤ n ==> m < Suc n
lemma le0:
0 ≤ n
lemma Suc_n_not_le_n:
¬ Suc n ≤ n
lemma le_0_eq:
(i ≤ 0) = (i = 0)
lemma le_Suc_eq:
(m ≤ Suc n) = (m ≤ n ∨ m = Suc n)
lemma le_SucE:
[| m ≤ Suc n; m ≤ n ==> R; m = Suc n ==> R |] ==> R
lemma Suc_leI:
m < n ==> Suc m ≤ n
lemma Suc_leD:
Suc m ≤ n ==> m ≤ n
lemma Suc_le_lessD:
Suc m ≤ n ==> m < n
lemma Suc_le_eq:
(Suc m ≤ n) = (m < n)
lemma le_SucI:
m ≤ n ==> m ≤ Suc n
lemma less_imp_le:
m < n ==> m ≤ n
lemmas le_simps:
m < n ==> m ≤ n
(m < Suc n) = (m ≤ n)
(Suc m ≤ n) = (m < n)
lemmas le_simps:
m < n ==> m ≤ n
(m < Suc n) = (m ≤ n)
(Suc m ≤ n) = (m < n)
lemma le_imp_less_or_eq:
m ≤ n ==> m < n ∨ m = n
lemma less_or_eq_imp_le:
m < n ∨ m = n ==> m ≤ n
lemma le_eq_less_or_eq:
(m ≤ n) = (m < n ∨ m = n)
lemma eq_imp_le:
m = n ==> m ≤ n
lemma le_refl:
n ≤ n
lemma le_less_trans:
[| i ≤ j; j < k |] ==> i < k
lemma less_le_trans:
[| i < j; j ≤ k |] ==> i < k
lemma le_trans:
[| i ≤ j; j ≤ k |] ==> i ≤ k
lemma le_anti_sym:
[| m ≤ n; n ≤ m |] ==> m = n
lemma Suc_le_mono:
(Suc n ≤ Suc m) = (n ≤ m)
lemma nat_less_le:
(m < n) = (m ≤ n ∧ m ≠ n)
lemma le_neq_implies_less:
[| m ≤ n; m ≠ n |] ==> m < n
lemma nat_le_linear:
m ≤ n ∨ n ≤ m
lemmas linorder_neqE_nat:
[| x ≠ y; x < y ==> R; y < x ==> R |] ==> R
lemmas linorder_neqE_nat:
[| x ≠ y; x < y ==> R; y < x ==> R |] ==> R
lemma not_less_less_Suc_eq:
¬ n < m ==> (n < Suc m) = (n = m)
lemma le_less_Suc_eq:
m ≤ n ==> (n < Suc m) = (n = m)
lemmas not_less_simps:
¬ n < m ==> (n < Suc m) = (n = m)
m ≤ n ==> (n < Suc m) = (n = m)
lemmas not_less_simps:
¬ n < m ==> (n < Suc m) = (n = m)
m ≤ n ==> (n < Suc m) = (n = m)
lemma zero_reorient:
((0::'a) = x) = (x = (0::'a))
lemma one_reorient:
((1::'a) = x) = (x = (1::'a))
lemma def_nat_rec_0:
(!!n. f n == nat_rec c h n) ==> f 0 = c
lemma def_nat_rec_Suc:
(!!n. f n == nat_rec c h n) ==> f (Suc n) = h n (f n)
lemma not0_implies_Suc:
n ≠ 0 ==> ∃m. n = Suc m
lemma gr_implies_not0:
m < n ==> n ≠ 0
lemma neq0_conv:
(n ≠ 0) = (0 < n)
lemma gr0I:
(n = 0 ==> False) ==> 0 < n
lemma gr0_conv_Suc:
(0 < n) = (∃m. n = Suc m)
lemma not_gr0:
(¬ 0 < n) = (n = 0)
lemma Suc_le_D:
Suc n ≤ m' ==> ∃m. m' = Suc m
lemma less_Suc_eq_0_disj:
(m < Suc n) = (m = 0 ∨ (∃j. m = Suc j ∧ j < n))
lemma nat_induct2:
[| P 0; P (Suc 0); !!k. P k ==> P (Suc (Suc k)) |] ==> P n
lemma Least_Suc:
[| P n; ¬ P 0 |] ==> (LEAST n. P n) = Suc (LEAST m. P (Suc m))
lemma Least_Suc2:
[| P n; Q m; ¬ P 0; ∀k. P (Suc k) = Q k |] ==> Least P = Suc (Least Q)
lemma min_0L:
min 0 n = 0
lemma min_0R:
min n 0 = 0
lemma min_Suc_Suc:
min (Suc m) (Suc n) = Suc (min m n)
lemma max_0L:
max 0 n = n
lemma max_0R:
max n 0 = n
lemma max_Suc_Suc:
max (Suc m) (Suc n) = Suc (max m n)
lemma diff_0_eq_0:
0 - n = 0
lemma diff_Suc_Suc:
Suc m - Suc n = m - n
lemma Suc_pred:
0 < n ==> Suc (n - Suc 0) = n
lemma add_0_right:
m + 0 = m
lemma add_Suc_right:
m + Suc n = Suc (m + n)
lemma
Suc m + n = m + Suc n
lemma nat_add_assoc:
m + n + k = m + (n + k)
lemma nat_add_commute:
m + n = n + m
lemma nat_add_left_commute:
x + (y + z) = y + (x + z)
lemma nat_add_left_cancel:
(k + m = k + n) = (m = n)
lemma nat_add_right_cancel:
(m + k = n + k) = (m = n)
lemma nat_add_left_cancel_le:
(k + m ≤ k + n) = (m ≤ n)
lemma nat_add_left_cancel_less:
(k + m < k + n) = (m < n)
lemma add_is_0:
(m + n = 0) = (m = 0 ∧ n = 0)
lemma add_is_1:
(m + n = Suc 0) = (m = Suc 0 ∧ n = 0 ∨ m = 0 ∧ n = Suc 0)
lemma one_is_add:
(Suc 0 = m + n) = (m = Suc 0 ∧ n = 0 ∨ m = 0 ∧ n = Suc 0)
lemma add_gr_0:
(0 < m + n) = (0 < m ∨ 0 < n)
lemma add_eq_self_zero:
m + n = m ==> n = 0
lemma inj_on_add_nat:
inj_on (%n. n + k) N
lemma mult_0_right:
m * 0 = 0
lemma mult_Suc_right:
m * Suc n = m + m * n
lemma nat_mult_commute:
m * n = n * m
lemma add_mult_distrib:
(m + n) * k = m * k + n * k
lemma add_mult_distrib2:
k * (m + n) = k * m + k * n
lemma nat_mult_assoc:
m * n * k = m * (n * k)
lemma mult_is_0:
(m * n = 0) = (m = 0 ∨ n = 0)
lemma add_less_mono1:
i < j ==> i + k < j + k
lemma add_less_mono:
[| i < j; k < l |] ==> i + k < j + l
lemma less_imp_Suc_add:
m < n ==> ∃k. n = Suc (m + k)
lemma mult_less_mono2:
[| i < j; 0 < k |] ==> k * i < k * j
lemma nat_mult_1:
1 * n = n
lemma nat_mult_1_right:
n * 1 = n
lemma less_mono_imp_le_mono:
[| !!i j. i < j ==> f i < f j; i ≤ j |] ==> f i ≤ f j
lemma add_le_mono1:
i ≤ j ==> i + k ≤ j + k
lemma add_le_mono:
[| i ≤ j; k ≤ l |] ==> i + k ≤ j + l
lemma le_add2:
n ≤ m + n
lemma le_add1:
n ≤ n + m
lemma less_add_Suc1:
i < Suc (i + m)
lemma less_add_Suc2:
i < Suc (m + i)
lemma less_iff_Suc_add:
(m < n) = (∃k. n = Suc (m + k))
lemma trans_le_add1:
i ≤ j ==> i ≤ j + m
lemma trans_le_add2:
i ≤ j ==> i ≤ m + j
lemma trans_less_add1:
i < j ==> i < j + m
lemma trans_less_add2:
i < j ==> i < m + j
lemma add_lessD1:
i + j < k ==> i < k
lemma not_add_less1:
¬ i + j < i
lemma not_add_less2:
¬ j + i < i
lemma add_leD1:
m + k ≤ n ==> m ≤ n
lemma add_leD2:
m + k ≤ n ==> k ≤ n
lemma add_leE:
[| m + k ≤ n; [| m ≤ n; k ≤ n |] ==> R |] ==> R
lemma less_add_eq_less:
[| k < l; m + l = k + n |] ==> m < n
lemma diff_self_eq_0:
m - m = 0
lemma add_diff_inverse:
¬ m < n ==> n + (m - n) = m
lemma le_add_diff_inverse:
n ≤ m ==> n + (m - n) = m
lemma le_add_diff_inverse2:
n ≤ m ==> m - n + n = m
lemma Suc_diff_le:
n ≤ m ==> Suc m - n = Suc (m - n)
lemma diff_less_Suc:
m - n < Suc m
lemma diff_le_self:
m - n ≤ m
lemma less_imp_diff_less:
j < k ==> j - n < k
lemma diff_diff_left:
i - j - k = i - (j + k)
lemma Suc_diff_diff:
Suc m - n - Suc k = m - n - k
lemma diff_Suc_less:
0 < n ==> n - Suc i < n
lemma diff_commute:
i - j - k = i - k - j
lemma diff_add_assoc:
k ≤ j ==> i + j - k = i + (j - k)
lemma diff_add_assoc2:
k ≤ j ==> j + i - k = j - k + i
lemma diff_add_inverse:
n + m - n = m
lemma diff_add_inverse2:
m + n - n = m
lemma le_imp_diff_is_add:
i ≤ j ==> (j - i = k) = (j = k + i)
lemma diff_is_0_eq:
(m - n = 0) = (m ≤ n)
lemma diff_is_0_eq':
m ≤ n ==> m - n = 0
lemma zero_less_diff:
(0 < n - m) = (m < n)
lemma less_imp_add_positive:
i < j ==> ∃k>0. i + k = j
lemma zero_induct_lemma:
[| P k; !!n. P (Suc n) ==> P n |] ==> P (k - i)
lemma zero_induct:
[| P k; !!n. P (Suc n) ==> P n |] ==> P 0
lemma diff_cancel:
k + m - (k + n) = m - n
lemma diff_cancel2:
m + k - (n + k) = m - n
lemma diff_add_0:
n - (n + m) = 0
lemma diff_mult_distrib:
(m - n) * k = m * k - n * k
lemma diff_mult_distrib2:
k * (m - n) = k * m - k * n
lemmas nat_distrib:
(m + n) * k = m * k + n * k
k * (m + n) = k * m + k * n
(m - n) * k = m * k - n * k
k * (m - n) = k * m - k * n
lemmas nat_distrib:
(m + n) * k = m * k + n * k
k * (m + n) = k * m + k * n
(m - n) * k = m * k - n * k
k * (m - n) = k * m - k * n
lemma mult_le_mono1:
i ≤ j ==> i * k ≤ j * k
lemma mult_le_mono2:
i ≤ j ==> k * i ≤ k * j
lemma mult_le_mono:
[| i ≤ j; k ≤ l |] ==> i * k ≤ j * l
lemma mult_less_mono1:
[| i < j; 0 < k |] ==> i * k < j * k
lemma nat_0_less_mult_iff:
(0 < m * n) = (0 < m ∧ 0 < n)
lemma one_le_mult_iff:
(Suc 0 ≤ m * n) = (1 ≤ m ∧ 1 ≤ n)
lemma mult_eq_1_iff:
(m * n = Suc 0) = (m = 1 ∧ n = 1)
lemma one_eq_mult_iff:
(Suc 0 = m * n) = (m = 1 ∧ n = 1)
lemma mult_less_cancel2:
(m * k < n * k) = (0 < k ∧ m < n)
lemma mult_less_cancel1:
(k * m < k * n) = (0 < k ∧ m < n)
lemma mult_le_cancel1:
(k * m ≤ k * n) = (0 < k --> m ≤ n)
lemma mult_le_cancel2:
(m * k ≤ n * k) = (0 < k --> m ≤ n)
lemma mult_cancel2:
(m * k = n * k) = (m = n ∨ k = 0)
lemma mult_cancel1:
(k * m = k * n) = (m = n ∨ k = 0)
lemma Suc_mult_less_cancel1:
(Suc k * m < Suc k * n) = (m < n)
lemma Suc_mult_le_cancel1:
(Suc k * m ≤ Suc k * n) = (m ≤ n)
lemma Suc_mult_cancel1:
(Suc k * m = Suc k * n) = (m = n)
lemma mult_eq_self_implies_10:
m = m * n ==> n = 1 ∨ m = 0
theorem nat_rec_0:
nat_rec f1.0 f2.0 0 = f1.0
theorem nat_rec_Suc:
nat_rec f1.0 f2.0 (Suc nat) = f2.0 nat (nat_rec f1.0 f2.0 nat)
theorem nat_case_0:
nat_case f1.0 f2.0 0 = f1.0
theorem nat_case_Suc:
nat_case f1.0 f2.0 (Suc nat) = f2.0 nat