1 | include "cerco/BitVector.ma". |
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2 | include "cerco/Util.ma". |
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3 | |
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4 | definition nat_of_bool ≝ |
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5 | λb: bool. |
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6 | match b with |
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7 | [ false ⇒ O |
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8 | | true ⇒ S O |
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9 | ]. |
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10 | |
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11 | definition add_n_with_carry: |
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12 | ∀n: nat. ∀b, c: BitVector n. ∀carry: bool. (BitVector n) × (BitVector 3) ≝ |
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13 | λn: nat. |
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14 | λb: BitVector n. |
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15 | λc: BitVector n. |
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16 | λcarry: bool. |
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17 | let b_as_nat ≝ nat_of_bitvector n b in |
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18 | let c_as_nat ≝ nat_of_bitvector n c in |
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19 | let carry_as_nat ≝ nat_of_bool carry in |
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20 | let result_old ≝ b_as_nat + c_as_nat + carry_as_nat in |
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21 | let ac_flag ≝ geb ((modulus b_as_nat (2 * n)) + |
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22 | (modulus c_as_nat (2 * n)) + |
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23 | c_as_nat) (2 * n) in |
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24 | let bit_xxx ≝ geb ((modulus b_as_nat (2^(n - 1))) + |
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25 | (modulus c_as_nat (2^(n - 1))) + |
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26 | c_as_nat) (2^(n - 1)) in |
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27 | let result ≝ modulus result_old (2^n) in |
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28 | let cy_flag ≝ geb result_old (2^n) in |
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29 | let ov_flag ≝ exclusive_disjunction cy_flag bit_xxx in |
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30 | mk_pair ? ? (bitvector_of_nat n result) |
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31 | ([[ cy_flag ; ac_flag ; ov_flag ]]). |
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32 | |
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33 | definition sub_n_with_carry: ∀n: nat. ∀b,c: BitVector n. ∀carry: bool. (BitVector n) × (BitVector 3) ≝ |
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34 | λn: nat. |
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35 | λb: BitVector n. |
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36 | λc: BitVector n. |
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37 | λcarry: bool. |
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38 | let b_as_nat ≝ nat_of_bitvector n b in |
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39 | let c_as_nat ≝ nat_of_bitvector n c in |
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40 | let carry_as_nat ≝ nat_of_bool carry in |
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41 | let temporary ≝ (b_as_nat mod (2 * n)) - (c_as_nat mod (2 * n)) in |
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42 | let ac_flag ≝ ltb (b_as_nat mod (2 * n)) ((c_as_nat mod (2 * n)) + carry_as_nat) in |
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43 | let bit_six ≝ ltb (b_as_nat mod (2^(n - 1))) ((c_as_nat mod (2^(n - 1))) + carry_as_nat) in |
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44 | let 〈b',cy_flag〉 ≝ |
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45 | if geb b_as_nat (c_as_nat + carry_as_nat) then |
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46 | 〈b_as_nat, false〉 |
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47 | else |
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48 | 〈b_as_nat + (2^n), true〉 |
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49 | in |
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50 | let ov_flag ≝ exclusive_disjunction cy_flag bit_six in |
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51 | 〈bitvector_of_nat n ((b' - c_as_nat) - carry_as_nat), [[ cy_flag; ac_flag; ov_flag ]]〉. |
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52 | |
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53 | definition add_8_with_carry ≝ add_n_with_carry 8. |
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54 | definition add_16_with_carry ≝ add_n_with_carry 16. |
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55 | definition sub_8_with_carry ≝ sub_n_with_carry 8. |
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56 | definition sub_16_with_carry ≝ sub_n_with_carry 16. |
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57 | |
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58 | definition increment ≝ |
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59 | λn: nat. |
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60 | λb: BitVector n. |
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61 | let b_as_nat ≝ (nat_of_bitvector n b) + 1 in |
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62 | let overflow ≝ geb b_as_nat 2^n in |
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63 | match overflow with |
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64 | [ false ⇒ bitvector_of_nat n b_as_nat |
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65 | | true ⇒ zero n |
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66 | ]. |
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67 | |
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68 | definition decrement ≝ |
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69 | λn: nat. |
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70 | λb: BitVector n. |
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71 | let b_as_nat ≝ nat_of_bitvector n b in |
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72 | match b_as_nat with |
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73 | [ O ⇒ maximum n |
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74 | | S o ⇒ bitvector_of_nat n o |
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75 | ]. |
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76 | |
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77 | definition two_complement_negation ≝ |
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78 | λn: nat. |
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79 | λb: BitVector n. |
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80 | let new_b ≝ negation_bv n b in |
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81 | increment n new_b. |
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82 | |
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83 | definition addition_n ≝ |
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84 | λn: nat. |
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85 | λb, c: BitVector n. |
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86 | let 〈res,flags〉 ≝ add_n_with_carry n b c false in |
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87 | res. |
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88 | |
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89 | definition subtraction ≝ |
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90 | λn: nat. |
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91 | λb, c: BitVector n. |
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92 | addition_n n b (two_complement_negation n c). |
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93 | |
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94 | definition multiplication ≝ |
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95 | λn: nat. |
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96 | λb, c: BitVector n. |
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97 | let b_nat ≝ nat_of_bitvector ? b in |
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98 | let c_nat ≝ nat_of_bitvector ? c in |
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99 | let result ≝ b_nat * c_nat in |
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100 | bitvector_of_nat (n + n) result. |
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101 | |
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102 | definition division_u ≝ |
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103 | λn: nat. |
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104 | λb, c: BitVector n. |
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105 | let b_nat ≝ nat_of_bitvector ? b in |
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106 | let c_nat ≝ nat_of_bitvector ? c in |
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107 | match c_nat with |
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108 | [ O ⇒ None ? |
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109 | | _ ⇒ |
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110 | let result ≝ b_nat ÷ c_nat in |
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111 | Some ? (bitvector_of_nat n result) |
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112 | ]. |
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113 | |
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114 | alias id "option1" = "cic:/matita/basics/sums/option.ind(1,0,1)". |
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115 | |
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116 | definition division_s: ∀n. ∀b, c: BitVector n. option1 (BitVector n) ≝ |
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117 | λn. |
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118 | match n with |
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119 | [ O ⇒ λb, c. None ? |
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120 | | S p ⇒ λb, c: BitVector (S p). |
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121 | let b_sign_bit ≝ get_index_v ? ? b O ? in |
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122 | let c_sign_bit ≝ get_index_v ? ? c O ? in |
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123 | let b_as_nat ≝ nat_of_bitvector ? b in |
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124 | let c_as_nat ≝ nat_of_bitvector ? c in |
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125 | match c_as_nat with |
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126 | [ O ⇒ None ? |
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127 | | S o ⇒ |
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128 | match b_sign_bit with |
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129 | [ true ⇒ |
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130 | let temp_b ≝ b_as_nat - (2^p) in |
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131 | match c_sign_bit with |
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132 | [ true ⇒ |
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133 | let temp_c ≝ c_as_nat - (2^p) in |
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134 | Some ? (bitvector_of_nat ? (temp_b ÷ temp_c)) |
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135 | | false ⇒ |
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136 | let result ≝ (temp_b ÷ c_as_nat) + (2^p) in |
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137 | Some ? (bitvector_of_nat ? result) |
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138 | ] |
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139 | | false ⇒ |
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140 | match c_sign_bit with |
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141 | [ true ⇒ |
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142 | let temp_c ≝ c_as_nat - (2^p) in |
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143 | let result ≝ (b_as_nat ÷ temp_c) + (2^p) in |
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144 | Some ? (bitvector_of_nat ? result) |
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145 | | false ⇒ Some ? (bitvector_of_nat ? (b_as_nat ÷ c_as_nat)) |
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146 | ] |
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147 | ] |
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148 | ] |
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149 | ]. |
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150 | // |
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151 | qed. |
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152 | |
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153 | definition modulus_u ≝ |
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154 | λn. |
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155 | λb, c: BitVector n. |
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156 | let b_nat ≝ nat_of_bitvector ? b in |
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157 | let c_nat ≝ nat_of_bitvector ? c in |
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158 | let result ≝ modulus b_nat c_nat in |
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159 | bitvector_of_nat (n + n) result. |
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160 | |
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161 | definition modulus_s ≝ |
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162 | λn. |
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163 | λb, c: BitVector n. |
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164 | match division_s n b c with |
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165 | [ None ⇒ None ? |
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166 | | Some result ⇒ |
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167 | let 〈high_bits, low_bits〉 ≝ split bool ? n (multiplication n result c) in |
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168 | Some ? (subtraction n b low_bits) |
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169 | ]. |
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170 | |
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171 | definition lt_u ≝ |
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172 | λn. |
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173 | λb, c: BitVector n. |
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174 | let b_nat ≝ nat_of_bitvector ? b in |
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175 | let c_nat ≝ nat_of_bitvector ? c in |
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176 | ltb b_nat c_nat. |
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177 | |
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178 | definition gt_u ≝ λn, b, c. lt_u n c b. |
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179 | |
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180 | definition lte_u ≝ λn, b, c. ¬(gt_u n b c). |
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181 | |
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182 | definition gte_u ≝ λn, b, c. ¬(lt_u n b c). |
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183 | |
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184 | definition lt_s ≝ |
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185 | λn. |
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186 | λb, c: BitVector n. |
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187 | let 〈result, flags〉 ≝ sub_n_with_carry n b c false in |
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188 | let ov_flag ≝ get_index_v ? ? flags 2 ? in |
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189 | if ov_flag then |
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190 | true |
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191 | else |
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192 | ((match n return λn'.BitVector n' → bool with |
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193 | [ O ⇒ λ_.false |
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194 | | S o ⇒ |
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195 | λresult'.(get_index_v ? ? result' O ?) |
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196 | ]) result). |
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197 | // |
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198 | qed. |
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199 | |
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200 | definition gt_s ≝ λn,b,c. lt_s n c b. |
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201 | |
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202 | definition lte_s ≝ λn,b,c. ¬(gt_s n b c). |
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203 | |
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204 | definition gte_s ≝ λn. λb, c. ¬(lt_s n b c). |
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205 | |
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206 | alias symbol "greater_than_or_equal" (instance 1) = "nat greater than or equal prop". |
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207 | |
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208 | definition bitvector_of_bool: |
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209 | ∀n: nat. ∀b: bool. BitVector (S n) ≝ |
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210 | λn: nat. |
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211 | λb: bool. |
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212 | (pad n 1 [[b]])⌈n + 1 ↦ S n⌉. |
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213 | // |
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214 | qed. |
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215 | |
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216 | definition full_add ≝ |
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217 | λn: nat. |
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218 | λb, c: BitVector n. |
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219 | λd: Bit. |
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220 | fold_right2_i ? ? ? ( |
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221 | λn. |
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222 | λb1, b2: bool. |
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223 | λd: Bit × (BitVector n). |
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224 | let 〈c1,r〉 ≝ d in |
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225 | 〈(b1 ∧ b2) ∨ (c1 ∧ (b1 ∨ b2)), |
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226 | (exclusive_disjunction (exclusive_disjunction b1 b2) c1) ::: r〉) |
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227 | 〈d, [[ ]]〉 ? b c. |
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228 | |
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229 | definition half_add ≝ |
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230 | λn: nat. |
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231 | λb, c: BitVector n. |
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232 | full_add n b c false. |
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