4 |
4 |
5 Type "nat" is a linear order, and a datatype; arithmetic operators + - |
5 Type "nat" is a linear order, and a datatype; arithmetic operators + - |
6 and * (for div, mod and dvd, see theory Divides). |
6 and * (for div, mod and dvd, see theory Divides). |
7 *) |
7 *) |
8 |
8 |
9 Nat = NatDef + |
9 header {* Natural numbers *} |
10 |
10 |
11 (* type "nat" is a wellfounded linear order, and a datatype *) |
11 theory Nat = Wellfounded_Recursion: |
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12 |
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13 subsection {* Type @{text ind} *} |
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14 |
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15 typedecl ind |
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16 |
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17 consts |
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18 Zero_Rep :: ind |
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19 Suc_Rep :: "ind => ind" |
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20 |
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21 axioms |
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22 -- {* the axiom of infinity in 2 parts *} |
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23 inj_Suc_Rep: "inj Suc_Rep" |
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24 Suc_Rep_not_Zero_Rep: "Suc_Rep x ~= Zero_Rep" |
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25 |
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26 |
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27 subsection {* Type nat *} |
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28 |
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29 text {* Type definition *} |
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30 |
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31 consts |
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32 Nat :: "ind set" |
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33 |
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34 inductive Nat |
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35 intros |
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36 Zero_RepI: "Zero_Rep : Nat" |
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37 Suc_RepI: "i : Nat ==> Suc_Rep i : Nat" |
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38 |
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39 global |
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40 |
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41 typedef (open Nat) |
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42 nat = "Nat" by (rule exI, rule Nat.Zero_RepI) |
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43 |
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44 instance nat :: ord .. |
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45 instance nat :: zero .. |
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46 instance nat :: one .. |
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47 |
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48 |
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49 text {* Abstract constants and syntax *} |
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50 |
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51 consts |
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52 Suc :: "nat => nat" |
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53 pred_nat :: "(nat * nat) set" |
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54 |
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55 local |
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56 |
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57 defs |
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58 Zero_nat_def: "0 == Abs_Nat Zero_Rep" |
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59 Suc_def: "Suc == (%n. Abs_Nat (Suc_Rep (Rep_Nat n)))" |
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60 One_nat_def [simp]: "1 == Suc 0" |
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61 |
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62 -- {* nat operations *} |
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63 pred_nat_def: "pred_nat == {(m, n). n = Suc m}" |
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64 |
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65 less_def: "m < n == (m, n) : trancl pred_nat" |
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66 |
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67 le_def: "m <= (n::nat) == ~ (n < m)" |
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68 |
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69 |
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70 text {* Induction *} |
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71 |
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72 theorem nat_induct: "P 0 ==> (!!n. P n ==> P (Suc n)) ==> P n" |
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73 apply (unfold Zero_nat_def Suc_def) |
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74 apply (rule Rep_Nat_inverse [THEN subst]) -- {* types force good instantiation *} |
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75 apply (erule Rep_Nat [THEN Nat.induct]) |
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76 apply (rules elim: Abs_Nat_inverse [THEN subst]) |
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77 done |
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78 |
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79 |
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80 text {* Isomorphisms: @{text Abs_Nat} and @{text Rep_Nat} *} |
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81 |
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82 lemma inj_Rep_Nat: "inj Rep_Nat" |
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83 apply (rule inj_inverseI) |
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84 apply (rule Rep_Nat_inverse) |
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85 done |
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86 |
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87 lemma inj_on_Abs_Nat: "inj_on Abs_Nat Nat" |
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88 apply (rule inj_on_inverseI) |
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89 apply (erule Abs_Nat_inverse) |
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90 done |
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91 |
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92 text {* Distinctness of constructors *} |
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93 |
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94 lemma Suc_not_Zero [iff]: "Suc m ~= 0" |
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95 apply (unfold Zero_nat_def Suc_def) |
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96 apply (rule inj_on_Abs_Nat [THEN inj_on_contraD]) |
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97 apply (rule Suc_Rep_not_Zero_Rep) |
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98 apply (rule Rep_Nat Nat.Suc_RepI Nat.Zero_RepI)+ |
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99 done |
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100 |
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101 lemma Zero_not_Suc [iff]: "0 ~= Suc m" |
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102 by (rule not_sym, rule Suc_not_Zero not_sym) |
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103 |
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104 lemma Suc_neq_Zero: "Suc m = 0 ==> R" |
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105 by (rule notE, rule Suc_not_Zero) |
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106 |
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107 lemma Zero_neq_Suc: "0 = Suc m ==> R" |
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108 by (rule Suc_neq_Zero, erule sym) |
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109 |
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110 text {* Injectiveness of @{term Suc} *} |
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111 |
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112 lemma inj_Suc: "inj Suc" |
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113 apply (unfold Suc_def) |
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114 apply (rule injI) |
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115 apply (drule inj_on_Abs_Nat [THEN inj_onD]) |
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116 apply (rule Rep_Nat Nat.Suc_RepI)+ |
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117 apply (drule inj_Suc_Rep [THEN injD]) |
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118 apply (erule inj_Rep_Nat [THEN injD]) |
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119 done |
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120 |
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121 lemma Suc_inject: "Suc x = Suc y ==> x = y" |
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122 by (rule inj_Suc [THEN injD]) |
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123 |
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124 lemma Suc_Suc_eq [iff]: "(Suc m = Suc n) = (m = n)" |
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125 apply (rule iffI) |
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126 apply (erule Suc_inject) |
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127 apply (erule arg_cong) |
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128 done |
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129 |
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130 lemma nat_not_singleton: "(ALL x. x = (0::nat)) = False" |
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131 by auto |
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132 |
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133 text {* @{typ nat} is a datatype *} |
12 |
134 |
13 rep_datatype nat |
135 rep_datatype nat |
14 distinct Suc_not_Zero, Zero_not_Suc |
136 distinct Suc_not_Zero Zero_not_Suc |
15 inject Suc_Suc_eq |
137 inject Suc_Suc_eq |
16 induct nat_induct |
138 induction nat_induct |
17 |
139 |
18 instance nat :: order (le_refl,le_trans,le_anti_sym,nat_less_le) |
140 lemma n_not_Suc_n: "n ~= Suc n" |
19 instance nat :: linorder (nat_le_linear) |
141 by (induct n) simp_all |
20 instance nat :: wellorder (wf_less) |
142 |
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143 lemma Suc_n_not_n: "Suc t ~= t" |
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144 by (rule not_sym, rule n_not_Suc_n) |
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145 |
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146 text {* A special form of induction for reasoning |
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147 about @{term "m < n"} and @{term "m - n"} *} |
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148 |
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149 theorem diff_induct: "(!!x. P x 0) ==> (!!y. P 0 (Suc y)) ==> |
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150 (!!x y. P x y ==> P (Suc x) (Suc y)) ==> P m n" |
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151 apply (rule_tac x = "m" in spec) |
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152 apply (induct_tac n) |
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153 prefer 2 |
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154 apply (rule allI) |
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155 apply (induct_tac x) |
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156 apply rules+ |
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157 done |
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158 |
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159 subsection {* Basic properties of "less than" *} |
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160 |
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161 lemma wf_pred_nat: "wf pred_nat" |
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162 apply (unfold wf_def pred_nat_def) |
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163 apply clarify |
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164 apply (induct_tac x) |
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165 apply blast+ |
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166 done |
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167 |
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168 lemma wf_less: "wf {(x, y::nat). x < y}" |
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169 apply (unfold less_def) |
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170 apply (rule wf_pred_nat [THEN wf_trancl, THEN wf_subset]) |
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171 apply blast |
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172 done |
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173 |
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174 lemma less_eq: "((m, n) : pred_nat^+) = (m < n)" |
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175 apply (unfold less_def) |
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176 apply (rule refl) |
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177 done |
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178 |
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179 subsubsection {* Introduction properties *} |
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180 |
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181 lemma less_trans: "i < j ==> j < k ==> i < (k::nat)" |
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182 apply (unfold less_def) |
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183 apply (rule trans_trancl [THEN transD]) |
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184 apply assumption+ |
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185 done |
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186 |
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187 lemma lessI [iff]: "n < Suc n" |
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188 apply (unfold less_def pred_nat_def) |
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189 apply (simp add: r_into_trancl) |
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190 done |
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191 |
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192 lemma less_SucI: "i < j ==> i < Suc j" |
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193 apply (rule less_trans) |
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194 apply assumption |
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195 apply (rule lessI) |
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196 done |
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197 |
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198 lemma zero_less_Suc [iff]: "0 < Suc n" |
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199 apply (induct n) |
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200 apply (rule lessI) |
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201 apply (erule less_trans) |
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202 apply (rule lessI) |
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203 done |
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204 |
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205 subsubsection {* Elimination properties *} |
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206 |
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207 lemma less_not_sym: "n < m ==> ~ m < (n::nat)" |
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208 apply (unfold less_def) |
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209 apply (blast intro: wf_pred_nat wf_trancl [THEN wf_asym]) |
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210 done |
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211 |
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212 lemma less_asym: |
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213 assumes h1: "(n::nat) < m" and h2: "~ P ==> m < n" shows P |
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214 apply (rule contrapos_np) |
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215 apply (rule less_not_sym) |
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216 apply (rule h1) |
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217 apply (erule h2) |
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218 done |
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219 |
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220 lemma less_not_refl: "~ n < (n::nat)" |
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221 apply (unfold less_def) |
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222 apply (rule wf_pred_nat [THEN wf_trancl, THEN wf_not_refl]) |
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223 done |
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224 |
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225 lemma less_irrefl [elim!]: "(n::nat) < n ==> R" |
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226 by (rule notE, rule less_not_refl) |
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227 |
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228 lemma less_not_refl2: "n < m ==> m ~= (n::nat)" by blast |
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229 |
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230 lemma less_not_refl3: "(s::nat) < t ==> s ~= t" |
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231 by (rule not_sym, rule less_not_refl2) |
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232 |
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233 lemma lessE: |
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234 assumes major: "i < k" |
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235 and p1: "k = Suc i ==> P" and p2: "!!j. i < j ==> k = Suc j ==> P" |
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236 shows P |
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237 apply (rule major [unfolded less_def pred_nat_def, THEN tranclE]) |
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238 apply simp_all |
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239 apply (erule p1) |
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240 apply (rule p2) |
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241 apply (simp add: less_def pred_nat_def) |
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242 apply assumption |
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243 done |
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244 |
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245 lemma not_less0 [iff]: "~ n < (0::nat)" |
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246 by (blast elim: lessE) |
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247 |
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248 lemma less_zeroE: "(n::nat) < 0 ==> R" |
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249 by (rule notE, rule not_less0) |
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250 |
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251 lemma less_SucE: assumes major: "m < Suc n" |
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252 and less: "m < n ==> P" and eq: "m = n ==> P" shows P |
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253 apply (rule major [THEN lessE]) |
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254 apply (rule eq) |
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255 apply blast |
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256 apply (rule less) |
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257 apply blast |
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258 done |
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259 |
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260 lemma less_Suc_eq: "(m < Suc n) = (m < n | m = n)" |
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261 by (blast elim!: less_SucE intro: less_trans) |
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262 |
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263 lemma less_one [iff]: "(n < (1::nat)) = (n = 0)" |
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264 by (simp add: less_Suc_eq) |
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265 |
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266 lemma less_Suc0 [iff]: "(n < Suc 0) = (n = 0)" |
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267 by (simp add: less_Suc_eq) |
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268 |
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269 lemma Suc_mono: "m < n ==> Suc m < Suc n" |
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270 by (induct n) (fast elim: less_trans lessE)+ |
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271 |
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272 text {* "Less than" is a linear ordering *} |
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273 lemma less_linear: "m < n | m = n | n < (m::nat)" |
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274 apply (induct_tac m) |
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275 apply (induct_tac n) |
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276 apply (rule refl [THEN disjI1, THEN disjI2]) |
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277 apply (rule zero_less_Suc [THEN disjI1]) |
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278 apply (blast intro: Suc_mono less_SucI elim: lessE) |
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279 done |
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280 |
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281 lemma nat_neq_iff: "((m::nat) ~= n) = (m < n | n < m)" |
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282 using less_linear by blast |
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283 |
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284 lemma nat_less_cases: assumes major: "(m::nat) < n ==> P n m" |
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285 and eqCase: "m = n ==> P n m" and lessCase: "n<m ==> P n m" |
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286 shows "P n m" |
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287 apply (rule less_linear [THEN disjE]) |
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288 apply (erule_tac [2] disjE) |
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289 apply (erule lessCase) |
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290 apply (erule sym [THEN eqCase]) |
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291 apply (erule major) |
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292 done |
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293 |
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294 |
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295 subsubsection {* Inductive (?) properties *} |
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296 |
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297 lemma Suc_lessI: "m < n ==> Suc m ~= n ==> Suc m < n" |
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298 apply (simp add: nat_neq_iff) |
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299 apply (blast elim!: less_irrefl less_SucE elim: less_asym) |
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300 done |
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301 |
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302 lemma Suc_lessD: "Suc m < n ==> m < n" |
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303 apply (induct n) |
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304 apply (fast intro!: lessI [THEN less_SucI] elim: less_trans lessE)+ |
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305 done |
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306 |
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307 lemma Suc_lessE: assumes major: "Suc i < k" |
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308 and minor: "!!j. i < j ==> k = Suc j ==> P" shows P |
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309 apply (rule major [THEN lessE]) |
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310 apply (erule lessI [THEN minor]) |
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311 apply (erule Suc_lessD [THEN minor]) |
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312 apply assumption |
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313 done |
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314 |
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315 lemma Suc_less_SucD: "Suc m < Suc n ==> m < n" |
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316 by (blast elim: lessE dest: Suc_lessD) |
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317 |
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318 lemma Suc_less_eq [iff]: "(Suc m < Suc n) = (m < n)" |
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319 apply (rule iffI) |
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320 apply (erule Suc_less_SucD) |
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321 apply (erule Suc_mono) |
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322 done |
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323 |
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324 lemma less_trans_Suc: |
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325 assumes le: "i < j" shows "j < k ==> Suc i < k" |
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326 apply (induct k) |
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327 apply simp_all |
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328 apply (insert le) |
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329 apply (simp add: less_Suc_eq) |
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330 apply (blast dest: Suc_lessD) |
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331 done |
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332 |
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333 text {* Can be used with @{text less_Suc_eq} to get @{term "n = m | n < m"} *} |
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334 lemma not_less_eq: "(~ m < n) = (n < Suc m)" |
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335 apply (rule_tac m = "m" and n = "n" in diff_induct) |
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336 apply simp_all |
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337 done |
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338 |
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339 text {* Complete induction, aka course-of-values induction *} |
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340 lemma nat_less_induct: |
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341 assumes prem: "!!n. ALL m::nat. m < n --> P m ==> P n" shows "P n" |
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342 apply (rule_tac a=n in wf_induct) |
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343 apply (rule wf_pred_nat [THEN wf_trancl]) |
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344 apply (rule prem) |
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345 apply (unfold less_def) |
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346 apply assumption |
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347 done |
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348 |
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349 subsection {* Properties of "less or equal than" *} |
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350 |
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351 text {* Was @{text le_eq_less_Suc}, but this orientation is more useful *} |
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352 lemma less_Suc_eq_le: "(m < Suc n) = (m <= n)" |
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353 by (unfold le_def, rule not_less_eq [symmetric]) |
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354 |
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355 lemma le_imp_less_Suc: "m <= n ==> m < Suc n" |
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356 by (rule less_Suc_eq_le [THEN iffD2]) |
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357 |
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358 lemma le0 [iff]: "(0::nat) <= n" |
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359 by (unfold le_def, rule not_less0) |
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360 |
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361 lemma Suc_n_not_le_n: "~ Suc n <= n" |
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362 by (simp add: le_def) |
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363 |
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364 lemma le_0_eq [iff]: "((i::nat) <= 0) = (i = 0)" |
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365 by (induct i) (simp_all add: le_def) |
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366 |
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367 lemma le_Suc_eq: "(m <= Suc n) = (m <= n | m = Suc n)" |
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368 by (simp del: less_Suc_eq_le add: less_Suc_eq_le [symmetric] less_Suc_eq) |
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369 |
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370 lemma le_SucE: "m <= Suc n ==> (m <= n ==> R) ==> (m = Suc n ==> R) ==> R" |
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371 by (drule le_Suc_eq [THEN iffD1], rules+) |
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372 |
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373 lemma leI: "~ n < m ==> m <= (n::nat)" by (simp add: le_def) |
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374 |
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375 lemma leD: "m <= n ==> ~ n < (m::nat)" |
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376 by (simp add: le_def) |
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377 |
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378 lemmas leE = leD [elim_format] |
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379 |
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380 lemma not_less_iff_le: "(~ n < m) = (m <= (n::nat))" |
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381 by (blast intro: leI elim: leE) |
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382 |
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383 lemma not_leE: "~ m <= n ==> n<(m::nat)" |
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384 by (simp add: le_def) |
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385 |
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386 lemma not_le_iff_less: "(~ n <= m) = (m < (n::nat))" |
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387 by (simp add: le_def) |
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388 |
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389 lemma Suc_leI: "m < n ==> Suc(m) <= n" |
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390 apply (simp add: le_def less_Suc_eq) |
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391 apply (blast elim!: less_irrefl less_asym) |
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392 done -- {* formerly called lessD *} |
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393 |
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394 lemma Suc_leD: "Suc(m) <= n ==> m <= n" |
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395 by (simp add: le_def less_Suc_eq) |
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396 |
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397 text {* Stronger version of @{text Suc_leD} *} |
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398 lemma Suc_le_lessD: "Suc m <= n ==> m < n" |
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399 apply (simp add: le_def less_Suc_eq) |
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400 using less_linear |
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401 apply blast |
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402 done |
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403 |
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404 lemma Suc_le_eq: "(Suc m <= n) = (m < n)" |
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405 by (blast intro: Suc_leI Suc_le_lessD) |
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406 |
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407 lemma le_SucI: "m <= n ==> m <= Suc n" |
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408 by (unfold le_def) (blast dest: Suc_lessD) |
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409 |
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410 lemma less_imp_le: "m < n ==> m <= (n::nat)" |
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411 by (unfold le_def) (blast elim: less_asym) |
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412 |
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413 text {* For instance, @{text "(Suc m < Suc n) = (Suc m <= n) = (m < n)"} *} |
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414 lemmas le_simps = less_imp_le less_Suc_eq_le Suc_le_eq |
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415 |
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416 |
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417 text {* Equivalence of @{term "m <= n"} and @{term "m < n | m = n"} *} |
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418 |
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419 lemma le_imp_less_or_eq: "m <= n ==> m < n | m = (n::nat)" |
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420 apply (unfold le_def) |
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421 using less_linear |
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422 apply (blast elim: less_irrefl less_asym) |
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423 done |
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424 |
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425 lemma less_or_eq_imp_le: "m < n | m = n ==> m <= (n::nat)" |
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426 apply (unfold le_def) |
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427 using less_linear |
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428 apply (blast elim!: less_irrefl elim: less_asym) |
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429 done |
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430 |
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431 lemma le_eq_less_or_eq: "(m <= (n::nat)) = (m < n | m=n)" |
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432 by (rules intro: less_or_eq_imp_le le_imp_less_or_eq) |
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433 |
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434 text {* Useful with @{text Blast}. *} |
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435 lemma eq_imp_le: "(m::nat) = n ==> m <= n" |
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436 by (rule less_or_eq_imp_le, rule disjI2) |
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437 |
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438 lemma le_refl: "n <= (n::nat)" |
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439 by (simp add: le_eq_less_or_eq) |
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440 |
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441 lemma le_less_trans: "[| i <= j; j < k |] ==> i < (k::nat)" |
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442 by (blast dest!: le_imp_less_or_eq intro: less_trans) |
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443 |
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444 lemma less_le_trans: "[| i < j; j <= k |] ==> i < (k::nat)" |
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445 by (blast dest!: le_imp_less_or_eq intro: less_trans) |
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446 |
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447 lemma le_trans: "[| i <= j; j <= k |] ==> i <= (k::nat)" |
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448 by (blast dest!: le_imp_less_or_eq intro: less_or_eq_imp_le less_trans) |
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449 |
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450 lemma le_anti_sym: "[| m <= n; n <= m |] ==> m = (n::nat)" |
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451 -- {* @{text order_less_irrefl} could make this proof fail *} |
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452 by (blast dest!: le_imp_less_or_eq elim!: less_irrefl elim: less_asym) |
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453 |
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454 lemma Suc_le_mono [iff]: "(Suc n <= Suc m) = (n <= m)" |
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455 by (simp add: le_simps) |
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456 |
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457 text {* Axiom @{text order_less_le} of class @{text order}: *} |
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458 lemma nat_less_le: "((m::nat) < n) = (m <= n & m ~= n)" |
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459 by (simp add: le_def nat_neq_iff) (blast elim!: less_asym) |
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460 |
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461 lemma le_neq_implies_less: "(m::nat) <= n ==> m ~= n ==> m < n" |
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462 by (rule iffD2, rule nat_less_le, rule conjI) |
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463 |
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464 text {* Axiom @{text linorder_linear} of class @{text linorder}: *} |
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465 lemma nat_le_linear: "(m::nat) <= n | n <= m" |
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466 apply (simp add: le_eq_less_or_eq) |
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467 using less_linear |
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468 apply blast |
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469 done |
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470 |
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471 lemma not_less_less_Suc_eq: "~ n < m ==> (n < Suc m) = (n = m)" |
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472 by (blast elim!: less_SucE) |
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473 |
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474 |
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475 text {* |
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476 Rewrite @{term "n < Suc m"} to @{term "n = m"} |
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477 if @{term "~ n < m"} or @{term "m <= n"} hold. |
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478 Not suitable as default simprules because they often lead to looping |
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479 *} |
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480 lemma le_less_Suc_eq: "m <= n ==> (n < Suc m) = (n = m)" |
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481 by (rule not_less_less_Suc_eq, rule leD) |
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482 |
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483 lemmas not_less_simps = not_less_less_Suc_eq le_less_Suc_eq |
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484 |
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485 |
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486 text {* |
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487 Re-orientation of the equations @{text "0 = x"} and @{text "1 = x"}. |
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488 No longer added as simprules (they loop) |
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489 but via @{text reorient_simproc} in Bin |
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490 *} |
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491 |
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492 text {* Polymorphic, not just for @{typ nat} *} |
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493 lemma zero_reorient: "(0 = x) = (x = 0)" |
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494 by auto |
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495 |
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496 lemma one_reorient: "(1 = x) = (x = 1)" |
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497 by auto |
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498 |
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499 text {* Type {@typ nat} is a wellfounded linear order *} |
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500 |
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501 instance nat :: order by (intro_classes, |
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502 (assumption | rule le_refl le_trans le_anti_sym nat_less_le)+) |
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503 instance nat :: linorder by (intro_classes, rule nat_le_linear) |
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504 instance nat :: wellorder by (intro_classes, rule wf_less) |
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505 |
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506 subsection {* Arithmetic operators *} |
21 |
507 |
22 axclass power < type |
508 axclass power < type |
23 |
509 |
24 consts |
510 consts |
25 power :: ['a::power, nat] => 'a (infixr "^" 80) |
511 power :: "('a::power) => nat => 'a" (infixr "^" 80) |
26 |
512 |
27 |
513 |
28 (* arithmetic operators + - and * *) |
514 text {* arithmetic operators @{text "+ -"} and @{text "*"} *} |
29 |
515 |
30 instance |
516 instance nat :: plus .. |
31 nat :: {plus, minus, times, power} |
517 instance nat :: minus .. |
32 |
518 instance nat :: times .. |
33 (* size of a datatype value; overloaded *) |
519 instance nat :: power .. |
34 consts size :: 'a => nat |
520 |
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521 text {* size of a datatype value; overloaded *} |
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522 consts size :: "'a => nat" |
35 |
523 |
36 primrec |
524 primrec |
37 add_0 "0 + n = n" |
525 add_0: "0 + n = n" |
38 add_Suc "Suc m + n = Suc(m + n)" |
526 add_Suc: "Suc m + n = Suc (m + n)" |
39 |
527 |
40 primrec |
528 primrec |
41 diff_0 "m - 0 = m" |
529 diff_0: "m - 0 = m" |
42 diff_Suc "m - Suc n = (case m - n of 0 => 0 | Suc k => k)" |
530 diff_Suc: "m - Suc n = (case m - n of 0 => 0 | Suc k => k)" |
43 |
531 |
44 primrec |
532 primrec |
45 mult_0 "0 * n = 0" |
533 mult_0: "0 * n = 0" |
46 mult_Suc "Suc m * n = n + (m * n)" |
534 mult_Suc: "Suc m * n = n + (m * n)" |
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535 |
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536 text {* These 2 rules ease the use of primitive recursion. NOTE USE OF @{text "=="} *} |
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537 lemma def_nat_rec_0: "(!!n. f n == nat_rec c h n) ==> f 0 = c" |
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538 by simp |
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539 |
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540 lemma def_nat_rec_Suc: "(!!n. f n == nat_rec c h n) ==> f (Suc n) = h n (f n)" |
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541 by simp |
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542 |
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543 lemma not0_implies_Suc: "n ~= 0 ==> EX m. n = Suc m" |
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544 by (case_tac n) simp_all |
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545 |
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546 lemma gr_implies_not0: "!!n::nat. m<n ==> n ~= 0" |
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547 by (case_tac n) simp_all |
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548 |
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549 lemma neq0_conv [iff]: "!!n::nat. (n ~= 0) = (0 < n)" |
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550 by (case_tac n) simp_all |
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551 |
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552 text {* This theorem is useful with @{text blast} *} |
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553 lemma gr0I: "((n::nat) = 0 ==> False) ==> 0 < n" |
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554 by (rule iffD1, rule neq0_conv, rules) |
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555 |
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556 lemma gr0_conv_Suc: "(0 < n) = (EX m. n = Suc m)" |
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557 by (fast intro: not0_implies_Suc) |
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558 |
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559 lemma not_gr0 [iff]: "!!n::nat. (~ (0 < n)) = (n = 0)" |
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560 apply (rule iffI) |
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561 apply (rule ccontr) |
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562 apply simp_all |
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563 done |
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564 |
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565 lemma Suc_le_D: "(Suc n <= m') ==> (? m. m' = Suc m)" |
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566 by (induct m') simp_all |
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567 |
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568 text {* Useful in certain inductive arguments *} |
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569 lemma less_Suc_eq_0_disj: "(m < Suc n) = (m = 0 | (EX j. m = Suc j & j < n))" |
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570 by (case_tac m) simp_all |
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571 |
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572 lemma nat_induct2: "P 0 ==> P (Suc 0) ==> (!!k. P k ==> P (Suc (Suc k))) ==> P n" |
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573 apply (rule nat_less_induct) |
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574 apply (case_tac n) |
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575 apply (case_tac [2] nat) |
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576 apply (blast intro: less_trans)+ |
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577 done |
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578 |
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579 subsection {* @{text LEAST} theorems for type @{typ nat} by specialization *} |
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580 |
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581 lemmas LeastI = wellorder_LeastI |
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582 lemmas Least_le = wellorder_Least_le |
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583 lemmas not_less_Least = wellorder_not_less_Least |
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584 |
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585 lemma Least_Suc: "[| P n; ~ P 0 |] ==> (LEAST n. P n) = Suc (LEAST m. P(Suc m))" |
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586 apply (case_tac "n") |
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587 apply auto |
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588 apply (frule LeastI) |
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589 apply (drule_tac P = "%x. P (Suc x) " in LeastI) |
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590 apply (subgoal_tac " (LEAST x. P x) <= Suc (LEAST x. P (Suc x))") |
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591 apply (erule_tac [2] Least_le) |
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592 apply (case_tac "LEAST x. P x") |
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593 apply auto |
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594 apply (drule_tac P = "%x. P (Suc x) " in Least_le) |
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595 apply (blast intro: order_antisym) |
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596 done |
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597 |
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598 lemma Least_Suc2: "[|P n; Q m; ~P 0; !k. P (Suc k) = Q k|] ==> Least P = Suc (Least Q)" |
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599 apply (erule (1) Least_Suc [THEN ssubst]) |
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600 apply simp |
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601 done |
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602 |
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603 |
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604 subsection {* @{term min} and @{term max} *} |
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605 |
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606 lemma min_0L [simp]: "min 0 n = (0::nat)" |
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607 by (rule min_leastL) simp |
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608 |
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609 lemma min_0R [simp]: "min n 0 = (0::nat)" |
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610 by (rule min_leastR) simp |
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611 |
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612 lemma min_Suc_Suc [simp]: "min (Suc m) (Suc n) = Suc (min m n)" |
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613 by (simp add: min_of_mono) |
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614 |
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615 lemma max_0L [simp]: "max 0 n = (n::nat)" |
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616 by (rule max_leastL) simp |
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617 |
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618 lemma max_0R [simp]: "max n 0 = (n::nat)" |
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619 by (rule max_leastR) simp |
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620 |
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621 lemma max_Suc_Suc [simp]: "max (Suc m) (Suc n) = Suc(max m n)" |
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622 by (simp add: max_of_mono) |
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623 |
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624 |
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625 subsection {* Basic rewrite rules for the arithmetic operators *} |
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626 |
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627 text {* Difference *} |
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628 |
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629 lemma diff_0_eq_0 [simp]: "0 - n = (0::nat)" |
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630 by (induct_tac n) simp_all |
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631 |
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632 lemma diff_Suc_Suc [simp]: "Suc(m) - Suc(n) = m - n" |
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633 by (induct_tac n) simp_all |
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634 |
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635 |
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636 text {* |
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637 Could be (and is, below) generalized in various ways |
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638 However, none of the generalizations are currently in the simpset, |
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639 and I dread to think what happens if I put them in |
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640 *} |
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641 lemma Suc_pred [simp]: "0 < n ==> Suc (n - Suc 0) = n" |
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642 by (simp split add: nat.split) |
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643 |
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644 declare diff_Suc [simp del] |
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645 |
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646 |
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647 subsection {* Addition *} |
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648 |
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649 lemma add_0_right [simp]: "m + 0 = (m::nat)" |
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650 by (induct m) simp_all |
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651 |
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652 lemma add_Suc_right [simp]: "m + Suc n = Suc (m + n)" |
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653 by (induct m) simp_all |
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654 |
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655 |
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656 text {* Associative law for addition *} |
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657 lemma add_assoc: "(m + n) + k = m + ((n + k)::nat)" |
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658 by (induct m) simp_all |
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659 |
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660 text {* Commutative law for addition *} |
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661 lemma add_commute: "m + n = n + (m::nat)" |
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662 by (induct m) simp_all |
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663 |
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664 lemma add_left_commute: "x + (y + z) = y + ((x + z)::nat)" |
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665 apply (rule mk_left_commute [of "op +"]) |
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666 apply (rule add_assoc) |
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667 apply (rule add_commute) |
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668 done |
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669 |
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670 text {* Addition is an AC-operator *} |
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671 lemmas add_ac = add_assoc add_commute add_left_commute |
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672 |
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673 lemma add_left_cancel [simp]: "(k + m = k + n) = (m = (n::nat))" |
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674 by (induct k) simp_all |
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675 |
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676 lemma add_right_cancel [simp]: "(m + k = n + k) = (m=(n::nat))" |
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677 by (induct k) simp_all |
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678 |
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679 lemma add_left_cancel_le [simp]: "(k + m <= k + n) = (m<=(n::nat))" |
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680 by (induct k) simp_all |
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681 |
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682 lemma add_left_cancel_less [simp]: "(k + m < k + n) = (m<(n::nat))" |
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683 by (induct k) simp_all |
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684 |
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685 text {* Reasoning about @{text "m + 0 = 0"}, etc. *} |
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686 |
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687 lemma add_is_0 [iff]: "!!m::nat. (m + n = 0) = (m = 0 & n = 0)" |
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688 by (case_tac m) simp_all |
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689 |
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690 lemma add_is_1: "(m+n= Suc 0) = (m= Suc 0 & n=0 | m=0 & n= Suc 0)" |
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691 by (case_tac m) simp_all |
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692 |
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693 lemma one_is_add: "(Suc 0 = m + n) = (m = Suc 0 & n = 0 | m = 0 & n = Suc 0)" |
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694 by (rule trans, rule eq_commute, rule add_is_1) |
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695 |
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696 lemma add_gr_0 [iff]: "!!m::nat. (0 < m + n) = (0 < m | 0 < n)" |
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697 by (simp del: neq0_conv add: neq0_conv [symmetric]) |
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698 |
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699 lemma add_eq_self_zero: "!!m::nat. m + n = m ==> n = 0" |
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700 apply (drule add_0_right [THEN ssubst]) |
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701 apply (simp add: add_assoc del: add_0_right) |
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702 done |
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703 |
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704 subsection {* Additional theorems about "less than" *} |
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705 |
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706 text {* Deleted @{text less_natE}; instead use @{text "less_imp_Suc_add RS exE"} *} |
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707 lemma less_imp_Suc_add: "m < n ==> (EX k. n = Suc (m + k))" |
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708 apply (induct n) |
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709 apply (simp_all add: order_le_less) |
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710 apply (blast elim!: less_SucE intro!: add_0_right [symmetric] add_Suc_right [symmetric]) |
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711 done |
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712 |
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713 lemma le_add2: "n <= ((m + n)::nat)" |
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714 apply (induct m) |
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715 apply simp_all |
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716 apply (erule le_SucI) |
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717 done |
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718 |
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719 lemma le_add1: "n <= ((n + m)::nat)" |
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720 apply (simp add: add_ac) |
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721 apply (rule le_add2) |
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722 done |
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723 |
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724 lemma less_add_Suc1: "i < Suc (i + m)" |
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725 by (rule le_less_trans, rule le_add1, rule lessI) |
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726 |
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727 lemma less_add_Suc2: "i < Suc (m + i)" |
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728 by (rule le_less_trans, rule le_add2, rule lessI) |
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729 |
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730 lemma less_iff_Suc_add: "(m < n) = (EX k. n = Suc (m + k))" |
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731 by (rules intro!: less_add_Suc1 less_imp_Suc_add) |
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732 |
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733 |
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734 lemma trans_le_add1: "(i::nat) <= j ==> i <= j + m" |
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735 by (rule le_trans, assumption, rule le_add1) |
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736 |
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737 lemma trans_le_add2: "(i::nat) <= j ==> i <= m + j" |
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738 by (rule le_trans, assumption, rule le_add2) |
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739 |
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740 lemma trans_less_add1: "(i::nat) < j ==> i < j + m" |
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741 by (rule less_le_trans, assumption, rule le_add1) |
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742 |
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743 lemma trans_less_add2: "(i::nat) < j ==> i < m + j" |
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744 by (rule less_le_trans, assumption, rule le_add2) |
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745 |
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746 lemma add_lessD1: "i + j < (k::nat) ==> i < k" |
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747 apply (induct j) |
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748 apply simp_all |
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749 apply (blast dest: Suc_lessD) |
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750 done |
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751 |
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752 lemma not_add_less1 [iff]: "~ (i + j < (i::nat))" |
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753 apply (rule notI) |
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754 apply (erule add_lessD1 [THEN less_irrefl]) |
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755 done |
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756 |
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757 lemma not_add_less2 [iff]: "~ (j + i < (i::nat))" |
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758 by (simp add: add_commute not_add_less1) |
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759 |
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760 lemma add_leD1: "m + k <= n ==> m <= (n::nat)" |
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761 by (induct k) (simp_all add: le_simps) |
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762 |
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763 lemma add_leD2: "m + k <= n ==> k <= (n::nat)" |
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764 apply (simp add: add_commute) |
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765 apply (erule add_leD1) |
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766 done |
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767 |
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768 lemma add_leE: "(m::nat) + k <= n ==> (m <= n ==> k <= n ==> R) ==> R" |
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769 by (blast dest: add_leD1 add_leD2) |
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770 |
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771 text {* needs @{text "!!k"} for @{text add_ac} to work *} |
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772 lemma less_add_eq_less: "!!k::nat. k < l ==> m + l = k + n ==> m < n" |
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773 by (force simp del: add_Suc_right |
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774 simp add: less_iff_Suc_add add_Suc_right [symmetric] add_ac) |
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775 |
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776 |
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777 subsection {* Monotonicity of Addition *} |
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778 |
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779 text {* strict, in 1st argument *} |
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780 lemma add_less_mono1: "i < j ==> i + k < j + (k::nat)" |
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781 by (induct k) simp_all |
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782 |
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783 text {* strict, in both arguments *} |
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784 lemma add_less_mono: "[|i < j; k < l|] ==> i + k < j + (l::nat)" |
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785 apply (rule add_less_mono1 [THEN less_trans]) |
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786 apply assumption+ |
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787 apply (induct_tac j) |
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788 apply simp_all |
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789 done |
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790 |
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791 text {* A [clumsy] way of lifting @{text "<"} |
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792 monotonicity to @{text "<="} monotonicity *} |
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793 lemma less_mono_imp_le_mono: |
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794 assumes lt_mono: "!!i j::nat. i < j ==> f i < f j" |
|
795 and le: "i <= j" shows "f i <= ((f j)::nat)" using le |
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796 apply (simp add: order_le_less) |
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797 apply (blast intro!: lt_mono) |
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798 done |
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799 |
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800 text {* non-strict, in 1st argument *} |
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801 lemma add_le_mono1: "i <= j ==> i + k <= j + (k::nat)" |
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802 apply (rule_tac f = "%j. j + k" in less_mono_imp_le_mono) |
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803 apply (erule add_less_mono1) |
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804 apply assumption |
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805 done |
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806 |
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807 text {* non-strict, in both arguments *} |
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808 lemma add_le_mono: "[| i <= j; k <= l |] ==> i + k <= j + (l::nat)" |
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809 apply (erule add_le_mono1 [THEN le_trans]) |
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810 apply (simp add: add_commute) |
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811 done |
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812 |
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813 |
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814 subsection {* Multiplication *} |
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815 |
|
816 text {* right annihilation in product *} |
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817 lemma mult_0_right [simp]: "(m::nat) * 0 = 0" |
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818 by (induct m) simp_all |
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819 |
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820 text {* right successor law for multiplication *} |
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821 lemma mult_Suc_right [simp]: "m * Suc n = m + (m * n)" |
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822 by (induct m) (simp_all add: add_ac) |
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823 |
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824 lemma mult_1: "(1::nat) * n = n" by simp |
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825 |
|
826 lemma mult_1_right: "n * (1::nat) = n" by simp |
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827 |
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828 text {* Commutative law for multiplication *} |
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829 lemma mult_commute: "m * n = n * (m::nat)" |
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830 by (induct m) simp_all |
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831 |
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832 text {* addition distributes over multiplication *} |
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833 lemma add_mult_distrib: "(m + n) * k = (m * k) + ((n * k)::nat)" |
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834 by (induct m) (simp_all add: add_ac) |
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835 |
|
836 lemma add_mult_distrib2: "k * (m + n) = (k * m) + ((k * n)::nat)" |
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837 by (induct m) (simp_all add: add_ac) |
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838 |
|
839 text {* Associative law for multiplication *} |
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840 lemma mult_assoc: "(m * n) * k = m * ((n * k)::nat)" |
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841 by (induct m) (simp_all add: add_mult_distrib) |
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842 |
|
843 lemma mult_left_commute: "x * (y * z) = y * ((x * z)::nat)" |
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844 apply (rule mk_left_commute [of "op *"]) |
|
845 apply (rule mult_assoc) |
|
846 apply (rule mult_commute) |
|
847 done |
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848 |
|
849 lemmas mult_ac = mult_assoc mult_commute mult_left_commute |
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850 |
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851 lemma mult_is_0 [simp]: "((m::nat) * n = 0) = (m=0 | n=0)" |
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852 apply (induct_tac m) |
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853 apply (induct_tac [2] n) |
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854 apply simp_all |
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855 done |
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856 |
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857 |
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858 subsection {* Difference *} |
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859 |
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860 lemma diff_self_eq_0 [simp]: "(m::nat) - m = 0" |
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861 by (induct m) simp_all |
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862 |
|
863 text {* Addition is the inverse of subtraction: |
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864 if @{term "n <= m"} then @{term "n + (m - n) = m"}. *} |
|
865 lemma add_diff_inverse: "~ m < n ==> n + (m - n) = (m::nat)" |
|
866 by (induct m n rule: diff_induct) simp_all |
|
867 |
|
868 lemma le_add_diff_inverse [simp]: "n <= m ==> n + (m - n) = (m::nat)" |
|
869 by (simp add: add_diff_inverse not_less_iff_le) |
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870 |
|
871 lemma le_add_diff_inverse2 [simp]: "n <= m ==> (m - n) + n = (m::nat)" |
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872 by (simp add: le_add_diff_inverse add_commute) |
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873 |
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874 |
|
875 subsection {* More results about difference *} |
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876 |
|
877 lemma Suc_diff_le: "n <= m ==> Suc m - n = Suc (m - n)" |
|
878 by (induct m n rule: diff_induct) simp_all |
|
879 |
|
880 lemma diff_less_Suc: "m - n < Suc m" |
|
881 apply (induct m n rule: diff_induct) |
|
882 apply (erule_tac [3] less_SucE) |
|
883 apply (simp_all add: less_Suc_eq) |
|
884 done |
|
885 |
|
886 lemma diff_le_self [simp]: "m - n <= (m::nat)" |
|
887 by (induct m n rule: diff_induct) (simp_all add: le_SucI) |
|
888 |
|
889 lemma less_imp_diff_less: "(j::nat) < k ==> j - n < k" |
|
890 by (rule le_less_trans, rule diff_le_self) |
|
891 |
|
892 lemma diff_diff_left: "(i::nat) - j - k = i - (j + k)" |
|
893 by (induct i j rule: diff_induct) simp_all |
|
894 |
|
895 lemma Suc_diff_diff [simp]: "(Suc m - n) - Suc k = m - n - k" |
|
896 by (simp add: diff_diff_left) |
|
897 |
|
898 lemma diff_Suc_less [simp]: "0<n ==> n - Suc i < n" |
|
899 apply (case_tac "n") |
|
900 apply safe |
|
901 apply (simp add: le_simps) |
|
902 done |
|
903 |
|
904 text {* This and the next few suggested by Florian Kammueller *} |
|
905 lemma diff_commute: "(i::nat) - j - k = i - k - j" |
|
906 by (simp add: diff_diff_left add_commute) |
|
907 |
|
908 lemma diff_add_assoc: "k <= (j::nat) ==> (i + j) - k = i + (j - k)" |
|
909 by (induct j k rule: diff_induct) simp_all |
|
910 |
|
911 lemma diff_add_assoc2: "k <= (j::nat) ==> (j + i) - k = (j - k) + i" |
|
912 by (simp add: add_commute diff_add_assoc) |
|
913 |
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914 lemma diff_add_inverse: "(n + m) - n = (m::nat)" |
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915 by (induct n) simp_all |
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916 |
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917 lemma diff_add_inverse2: "(m + n) - n = (m::nat)" |
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918 by (simp add: diff_add_assoc) |
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919 |
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920 lemma le_imp_diff_is_add: "i <= (j::nat) ==> (j - i = k) = (j = k + i)" |
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921 apply safe |
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922 apply (simp_all add: diff_add_inverse2) |
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923 done |
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924 |
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925 lemma diff_is_0_eq [simp]: "((m::nat) - n = 0) = (m <= n)" |
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926 by (induct m n rule: diff_induct) simp_all |
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927 |
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928 lemma diff_is_0_eq' [simp]: "m <= n ==> (m::nat) - n = 0" |
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929 by (rule iffD2, rule diff_is_0_eq) |
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930 |
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931 lemma zero_less_diff [simp]: "(0 < n - (m::nat)) = (m < n)" |
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932 by (induct m n rule: diff_induct) simp_all |
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933 |
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934 lemma less_imp_add_positive: "i < j ==> EX k::nat. 0 < k & i + k = j" |
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935 apply (rule_tac x = "j - i" in exI) |
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936 apply (simp (no_asm_simp) add: add_diff_inverse less_not_sym) |
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937 done |
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938 |
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939 lemma zero_induct_lemma: "P k ==> (!!n. P (Suc n) ==> P n) ==> P (k - i)" |
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940 apply (induct k i rule: diff_induct) |
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941 apply (simp_all (no_asm)) |
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942 apply rules |
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943 done |
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944 |
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945 lemma zero_induct: "P k ==> (!!n. P (Suc n) ==> P n) ==> P 0" |
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946 apply (rule diff_self_eq_0 [THEN subst]) |
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947 apply (rule zero_induct_lemma) |
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948 apply rules+ |
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949 done |
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950 |
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951 lemma diff_cancel: "(k + m) - (k + n) = m - (n::nat)" |
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952 by (induct k) simp_all |
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953 |
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954 lemma diff_cancel2: "(m + k) - (n + k) = m - (n::nat)" |
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955 by (simp add: diff_cancel add_commute) |
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956 |
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957 lemma diff_add_0: "n - (n + m) = (0::nat)" |
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958 by (induct n) simp_all |
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959 |
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960 |
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961 text {* Difference distributes over multiplication *} |
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962 |
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963 lemma diff_mult_distrib: "((m::nat) - n) * k = (m * k) - (n * k)" |
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964 by (induct m n rule: diff_induct) (simp_all add: diff_cancel) |
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965 |
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966 lemma diff_mult_distrib2: "k * ((m::nat) - n) = (k * m) - (k * n)" |
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967 by (simp add: diff_mult_distrib mult_commute [of k]) |
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968 -- {* NOT added as rewrites, since sometimes they are used from right-to-left *} |
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969 |
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970 lemmas nat_distrib = |
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971 add_mult_distrib add_mult_distrib2 diff_mult_distrib diff_mult_distrib2 |
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972 |
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973 |
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974 subsection {* Monotonicity of Multiplication *} |
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975 |
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976 lemma mult_le_mono1: "i <= (j::nat) ==> i * k <= j * k" |
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977 by (induct k) (simp_all add: add_le_mono) |
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978 |
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979 lemma mult_le_mono2: "i <= (j::nat) ==> k * i <= k * j" |
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980 apply (drule mult_le_mono1) |
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981 apply (simp add: mult_commute) |
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982 done |
|
983 |
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984 text {* @{text "<="} monotonicity, BOTH arguments *} |
|
985 lemma mult_le_mono: "i <= (j::nat) ==> k <= l ==> i * k <= j * l" |
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986 apply (erule mult_le_mono1 [THEN le_trans]) |
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987 apply (erule mult_le_mono2) |
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988 done |
|
989 |
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990 text {* strict, in 1st argument; proof is by induction on @{text "k > 0"} *} |
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991 lemma mult_less_mono2: "(i::nat) < j ==> 0 < k ==> k * i < k * j" |
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992 apply (erule_tac m1 = "0" in less_imp_Suc_add [THEN exE]) |
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993 apply simp |
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994 apply (induct_tac x) |
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995 apply (simp_all add: add_less_mono) |
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996 done |
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997 |
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998 lemma mult_less_mono1: "(i::nat) < j ==> 0 < k ==> i * k < j * k" |
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999 by (drule mult_less_mono2) (simp_all add: mult_commute) |
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1000 |
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1001 lemma zero_less_mult_iff [simp]: "(0 < (m::nat) * n) = (0 < m & 0 < n)" |
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1002 apply (induct m) |
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1003 apply (case_tac [2] n) |
|
1004 apply simp_all |
|
1005 done |
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1006 |
|
1007 lemma one_le_mult_iff [simp]: "(Suc 0 <= m * n) = (1 <= m & 1 <= n)" |
|
1008 apply (induct m) |
|
1009 apply (case_tac [2] n) |
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1010 apply simp_all |
|
1011 done |
|
1012 |
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1013 lemma mult_eq_1_iff [simp]: "(m * n = Suc 0) = (m = 1 & n = 1)" |
|
1014 apply (induct_tac m) |
|
1015 apply simp |
|
1016 apply (induct_tac n) |
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1017 apply simp |
|
1018 apply fastsimp |
|
1019 done |
|
1020 |
|
1021 lemma one_eq_mult_iff [simp]: "(Suc 0 = m * n) = (m = 1 & n = 1)" |
|
1022 apply (rule trans) |
|
1023 apply (rule_tac [2] mult_eq_1_iff) |
|
1024 apply fastsimp |
|
1025 done |
|
1026 |
|
1027 lemma mult_less_cancel2: "((m::nat) * k < n * k) = (0 < k & m < n)" |
|
1028 apply (safe intro!: mult_less_mono1) |
|
1029 apply (case_tac k) |
|
1030 apply auto |
|
1031 apply (simp del: le_0_eq add: linorder_not_le [symmetric]) |
|
1032 apply (blast intro: mult_le_mono1) |
|
1033 done |
|
1034 |
|
1035 lemma mult_less_cancel1 [simp]: "(k * (m::nat) < k * n) = (0 < k & m < n)" |
|
1036 by (simp add: mult_less_cancel2 mult_commute [of k]) |
|
1037 |
|
1038 declare mult_less_cancel2 [simp] |
|
1039 |
|
1040 lemma mult_le_cancel1 [simp]: "(k * (m::nat) <= k * n) = (0 < k --> m <= n)" |
|
1041 apply (simp add: linorder_not_less [symmetric]) |
|
1042 apply auto |
|
1043 done |
|
1044 |
|
1045 lemma mult_le_cancel2 [simp]: "((m::nat) * k <= n * k) = (0 < k --> m <= n)" |
|
1046 apply (simp add: linorder_not_less [symmetric]) |
|
1047 apply auto |
|
1048 done |
|
1049 |
|
1050 lemma mult_cancel2: "(m * k = n * k) = (m = n | (k = (0::nat)))" |
|
1051 apply (cut_tac less_linear) |
|
1052 apply safe |
|
1053 apply auto |
|
1054 apply (drule mult_less_mono1, assumption, simp)+ |
|
1055 done |
|
1056 |
|
1057 lemma mult_cancel1 [simp]: "(k * m = k * n) = (m = n | (k = (0::nat)))" |
|
1058 by (simp add: mult_cancel2 mult_commute [of k]) |
|
1059 |
|
1060 declare mult_cancel2 [simp] |
|
1061 |
|
1062 lemma Suc_mult_less_cancel1: "(Suc k * m < Suc k * n) = (m < n)" |
|
1063 by (subst mult_less_cancel1) simp |
|
1064 |
|
1065 lemma Suc_mult_le_cancel1: "(Suc k * m <= Suc k * n) = (m <= n)" |
|
1066 by (subst mult_le_cancel1) simp |
|
1067 |
|
1068 lemma Suc_mult_cancel1: "(Suc k * m = Suc k * n) = (m = n)" |
|
1069 by (subst mult_cancel1) simp |
|
1070 |
|
1071 |
|
1072 text {* Lemma for @{text gcd} *} |
|
1073 lemma mult_eq_self_implies_10: "(m::nat) = m * n ==> n = 1 | m = 0" |
|
1074 apply (drule sym) |
|
1075 apply (rule disjCI) |
|
1076 apply (rule nat_less_cases, erule_tac [2] _) |
|
1077 apply (fastsimp elim!: less_SucE) |
|
1078 apply (fastsimp dest: mult_less_mono2) |
|
1079 done |
47 |
1080 |
48 end |
1081 end |