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72
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1 module logic where
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2
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3 open import Level
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4 open import Relation.Nullary
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5 open import Relation.Binary
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6 open import Data.Empty
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7
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8
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9 data Bool : Set where
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10 true : Bool
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11 false : Bool
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12
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13 record _∧_ {n m : Level} (A : Set n) ( B : Set m ) : Set (n ⊔ m) where
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14 constructor ⟪_,_⟫
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15 field
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16 proj1 : A
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17 proj2 : B
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18
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19 data _∨_ {n m : Level} (A : Set n) ( B : Set m ) : Set (n ⊔ m) where
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20 case1 : A → A ∨ B
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21 case2 : B → A ∨ B
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22
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23 _⇔_ : {n m : Level } → ( A : Set n ) ( B : Set m ) → Set (n ⊔ m)
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24 _⇔_ A B = ( A → B ) ∧ ( B → A )
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25
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26 contra-position : {n m : Level } {A : Set n} {B : Set m} → (A → B) → ¬ B → ¬ A
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27 contra-position {n} {m} {A} {B} f ¬b a = ¬b ( f a )
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28
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29 double-neg : {n : Level } {A : Set n} → A → ¬ ¬ A
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30 double-neg A notnot = notnot A
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31
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32 double-neg2 : {n : Level } {A : Set n} → ¬ ¬ ¬ A → ¬ A
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33 double-neg2 notnot A = notnot ( double-neg A )
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34
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35 de-morgan : {n : Level } {A B : Set n} → A ∧ B → ¬ ( (¬ A ) ∨ (¬ B ) )
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36 de-morgan {n} {A} {B} and (case1 ¬A) = ⊥-elim ( ¬A ( _∧_.proj1 and ))
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37 de-morgan {n} {A} {B} and (case2 ¬B) = ⊥-elim ( ¬B ( _∧_.proj2 and ))
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38
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39 dont-or : {n m : Level} {A : Set n} { B : Set m } → A ∨ B → ¬ A → B
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40 dont-or {A} {B} (case1 a) ¬A = ⊥-elim ( ¬A a )
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41 dont-or {A} {B} (case2 b) ¬A = b
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42
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43 dont-orb : {n m : Level} {A : Set n} { B : Set m } → A ∨ B → ¬ B → A
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44 dont-orb {A} {B} (case2 b) ¬B = ⊥-elim ( ¬B b )
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45 dont-orb {A} {B} (case1 a) ¬B = a
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46
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47
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48 infixr 130 _∧_
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49 infixr 140 _∨_
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50 infixr 150 _⇔_
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51
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52 _/\_ : Bool → Bool → Bool
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53 true /\ true = true
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54 _ /\ _ = false
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55
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56 _\/_ : Bool → Bool → Bool
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57 false \/ false = false
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58 _ \/ _ = true
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59
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60 not_ : Bool → Bool
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61 not true = false
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62 not false = true
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63
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64 _<=>_ : Bool → Bool → Bool
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65 true <=> true = true
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66 false <=> false = true
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67 _ <=> _ = false
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68
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69 infixr 130 _\/_
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70 infixr 140 _/\_
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71
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72 open import Relation.Binary.PropositionalEquality
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73
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74 ≡-Bool-func : {A B : Bool } → ( A ≡ true → B ≡ true ) → ( B ≡ true → A ≡ true ) → A ≡ B
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75 ≡-Bool-func {true} {true} a→b b→a = refl
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76 ≡-Bool-func {false} {true} a→b b→a with b→a refl
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77 ... | ()
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78 ≡-Bool-func {true} {false} a→b b→a with a→b refl
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79 ... | ()
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80 ≡-Bool-func {false} {false} a→b b→a = refl
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81
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82 bool-≡-? : (a b : Bool) → Dec ( a ≡ b )
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83 bool-≡-? true true = yes refl
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84 bool-≡-? true false = no (λ ())
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85 bool-≡-? false true = no (λ ())
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86 bool-≡-? false false = yes refl
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87
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88 ¬-bool-t : {a : Bool} → ¬ ( a ≡ true ) → a ≡ false
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89 ¬-bool-t {true} ne = ⊥-elim ( ne refl )
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90 ¬-bool-t {false} ne = refl
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91
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92 ¬-bool-f : {a : Bool} → ¬ ( a ≡ false ) → a ≡ true
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93 ¬-bool-f {true} ne = refl
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94 ¬-bool-f {false} ne = ⊥-elim ( ne refl )
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95
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96 ¬-bool : {a : Bool} → a ≡ false → a ≡ true → ⊥
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97 ¬-bool refl ()
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98
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99 lemma-∧-0 : {a b : Bool} → a /\ b ≡ true → a ≡ false → ⊥
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100 lemma-∧-0 {true} {true} refl ()
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101 lemma-∧-0 {true} {false} ()
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102 lemma-∧-0 {false} {true} ()
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103 lemma-∧-0 {false} {false} ()
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104
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105 lemma-∧-1 : {a b : Bool} → a /\ b ≡ true → b ≡ false → ⊥
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106 lemma-∧-1 {true} {true} refl ()
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107 lemma-∧-1 {true} {false} ()
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108 lemma-∧-1 {false} {true} ()
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109 lemma-∧-1 {false} {false} ()
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110
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111 bool-and-tt : {a b : Bool} → a ≡ true → b ≡ true → ( a /\ b ) ≡ true
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112 bool-and-tt refl refl = refl
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113
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114 bool-∧→tt-0 : {a b : Bool} → ( a /\ b ) ≡ true → a ≡ true
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115 bool-∧→tt-0 {true} {true} refl = refl
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116 bool-∧→tt-0 {false} {_} ()
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117
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118 bool-∧→tt-1 : {a b : Bool} → ( a /\ b ) ≡ true → b ≡ true
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119 bool-∧→tt-1 {true} {true} refl = refl
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120 bool-∧→tt-1 {true} {false} ()
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121 bool-∧→tt-1 {false} {false} ()
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122
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123 bool-or-1 : {a b : Bool} → a ≡ false → ( a \/ b ) ≡ b
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124 bool-or-1 {false} {true} refl = refl
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125 bool-or-1 {false} {false} refl = refl
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126 bool-or-2 : {a b : Bool} → b ≡ false → (a \/ b ) ≡ a
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127 bool-or-2 {true} {false} refl = refl
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128 bool-or-2 {false} {false} refl = refl
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129
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130 bool-or-3 : {a : Bool} → ( a \/ true ) ≡ true
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131 bool-or-3 {true} = refl
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132 bool-or-3 {false} = refl
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133
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134 bool-or-31 : {a b : Bool} → b ≡ true → ( a \/ b ) ≡ true
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135 bool-or-31 {true} {true} refl = refl
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136 bool-or-31 {false} {true} refl = refl
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137
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138 bool-or-4 : {a : Bool} → ( true \/ a ) ≡ true
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139 bool-or-4 {true} = refl
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140 bool-or-4 {false} = refl
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141
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142 bool-or-41 : {a b : Bool} → a ≡ true → ( a \/ b ) ≡ true
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143 bool-or-41 {true} {b} refl = refl
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144
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145 bool-and-1 : {a b : Bool} → a ≡ false → (a /\ b ) ≡ false
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146 bool-and-1 {false} {b} refl = refl
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147 bool-and-2 : {a b : Bool} → b ≡ false → (a /\ b ) ≡ false
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148 bool-and-2 {true} {false} refl = refl
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149 bool-and-2 {false} {false} refl = refl
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150
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151
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