# source:Deliverables/D4.1/Matita/Arithmetic.ma@277

Last change on this file since 277 was 277, checked in by sacerdot, 10 years ago

Bugs fixed in definition of sub8_with_carrier.

File size: 4.4 KB
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1include "Universes.ma".
2include "Plogic/equality.ma".
3include "Connectives.ma".
4include "Nat.ma".
5include "Exponential.ma".
6include "Bool.ma".
7include "BitVector.ma".
8include "List.ma".
9
10ndefinition one ≝ S Z.
11ndefinition two ≝ (S(S(Z))).
12ndefinition three ≝ two + one.
13ndefinition four ≝ two + two.
14ndefinition five ≝ three + two.
15ndefinition six ≝ three + three.
16ndefinition seven ≝ three + four.
17ndefinition eight ≝ four + four.
18ndefinition nine ≝ five + four.
19ndefinition ten ≝ five + five.
20ndefinition eleven ≝ six + five.
21ndefinition twelve ≝ six + six.
22ndefinition thirteen ≝ seven + six.
23ndefinition fourteen ≝ seven + seven.
24ndefinition fifteen ≝ eight + seven.
25ndefinition sixteen ≝ eight + eight.
26ndefinition seventeen ≝ nine + eight.
27ndefinition eighteen ≝ nine + nine.
28ndefinition nineteen ≝ ten + nine.
29ndefinition one_hundred_and_twenty_eight ≝ sixteen * eight.
30ndefinition two_hundred_and_fifty_six ≝
31  one_hundred_and_twenty_eight + one_hundred_and_twenty_eight.
32
33ndefinition nat_of_bool ≝
34  λb: Bool.
35    match b with
36      [ false ⇒ Z
37      | true ⇒ S Z
38      ].
39
41      ∀n: Nat. ∀b, c: BitVector n. ∀carry: Bool. Cartesian (BitVector n) (List Bool) ≝
42  λn: Nat.
43  λb: BitVector n.
44  λc: BitVector n.
45  λcarry: Bool.
46    let b_as_nat ≝ nat_of_bitvector n b in
47    let c_as_nat ≝ nat_of_bitvector n c in
48    let carry_as_nat ≝ nat_of_bool carry in
49    let result_old ≝ b_as_nat + c_as_nat + carry_as_nat in
50    let ac_flag ≝ ((modulus b_as_nat ((S (S Z)) * n)) +
51                  (modulus c_as_nat ((S (S Z)) * n)) +
52                  c_as_nat) ≥ ((S (S Z)) * n) in
53    let bit_xxx ≝ (((modulus b_as_nat ((S (S Z))^(n - (S Z)))) +
54                  (modulus c_as_nat ((S (S Z))^(n - (S Z)))) +
55                  c_as_nat) ≥ ((S (S Z))^(n - (S Z)))) in
56    let result ≝ modulus result_old ((S (S Z))^n) in
57    let cy_flag ≝ (result_old ≥ ((S (S Z))^n)) in
58    let ov_flag ≝ exclusive_disjunction cy_flag bit_xxx in
59      ? (mk_Cartesian (BitVector n) ? (? (bitvector_of_nat n result))
60                          (cy_flag :: ac_flag :: ov_flag :: Empty Bool)).
61    #H; nassumption;
62nqed.
63
64ndefinition sub_8_with_carry: ∀b,c: BitVector eight. ∀carry: Bool. Cartesian (BitVector eight) (List Bool) ≝
65  λb: BitVector eight.
66  λc: BitVector eight.
67  λcarry: Bool.
68    let b_as_nat ≝ nat_of_bitvector eight b in
69    let c_as_nat ≝ nat_of_bitvector eight c in
70    let carry_as_nat ≝ nat_of_bool carry in
71    let temporary ≝ b_as_nat mod sixteen - c_as_nat mod sixteen in
72    let ac_flag ≝ negation (conjunction ((b_as_nat mod sixteen) ≤ (c_as_nat mod sixteen)) (temporary ≤ carry_as_nat)) in
73    let bit_six ≝ negation (conjunction ((b_as_nat mod one_hundred_and_twenty_eight) ≤ (c_as_nat mod one_hundred_and_twenty_eight)) (temporary ≤ carry_as_nat)) in
74    let old_result_1 ≝ b_as_nat - c_as_nat in
75    let old_result_2 ≝ old_result_1 - carry_as_nat in
76    let ov_flag ≝ exclusive_disjunction carry bit_six in
77      match conjunction (b_as_nat ≤ c_as_nat) (old_result_1 ≤ carry_as_nat) with
78        [ false ⇒
79           let cy_flag ≝ false in
80            〈 bitvector_of_nat eight old_result_2, [cy_flag ; ac_flag ; ov_flag ] 〉
81        | true ⇒
82           let cy_flag ≝ true in
83           let new_result ≝ b_as_nat + two_hundred_and_fifty_six - c_as_nat - carry_as_nat in
84            〈 bitvector_of_nat eight new_result, [ cy_flag ; ac_flag ; ov_flag ] 〉
85        ].
86
89
90ndefinition increment ≝
91  λn: Nat.
92  λb: BitVector n.
93    let b_as_nat ≝ (nat_of_bitvector n b) + (S Z) in
94    let overflow ≝ b_as_nat ≥ (S (S Z))^n in
95      match overflow with
96        [ false ⇒ bitvector_of_nat n b_as_nat
97        | true ⇒ zero n
98        ].
99
100ndefinition decrement ≝
101  λn: Nat.
102  λb: BitVector n.
103    let b_as_nat ≝ nat_of_bitvector n b in
104      match b_as_nat with
105        [ Z ⇒ max n
106        | S o ⇒ bitvector_of_nat n o
107        ].
108
109alias symbol "greater_than_or_equal" (instance 1) = "Nat greater than or equal prop".
110
111ndefinition bitvector_of_bool:
112      ∀n: Nat. ∀b: Bool. BitVector n ≝
113  λn: Nat.
114  λb: Bool.
115    ? (pad (n - (S Z)) (S Z) (Cons Bool ? b (Empty Bool))).
116  nrewrite > (plus_minus_inverse_right n ?);
117  #H;
118  nassumption;
119nqed.
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