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4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
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11 (* v GNU General Public License Version 2 *)
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15 include "models/nat_uniform.ma".
16 include "supremum.ma".
17 include "nat/le_arith.ma".
18 include "russell_support.ma".
20 inductive cmp_cases (n,m:nat) : CProp ≝
21 | cmp_lt : n < m → cmp_cases n m
22 | cmp_eq : n = m → cmp_cases n m
23 | cmp_gt : m < n → cmp_cases n m.
25 lemma cmp_nat: ∀n,m.cmp_cases n m.
26 intros; generalize in match (nat_compare_to_Prop n m);
27 cases (nat_compare n m); intros;
28 [constructor 1|constructor 2|constructor 3] assumption;
31 alias symbol "pi1" = "exT fst".
32 alias symbol "leq" = "natural 'less or equal to'".
33 lemma nat_dedekind_sigma_complete:
34 ∀l,u:ℕ.∀a:sequence {[l,u]}.a is_increasing →
35 ∀x.x is_supremum a → ∃i.∀j.i ≤ j → fst x = fst (a j).
36 intros 5; cases x (s Hs); clear x; letin X ≝ (〈s,Hs〉);
37 fold normalize X; intros; cases H1;
38 letin spec ≝ (λi,j:ℕ.(u≤i ∧ s = fst (a j)) ∨ (i < u ∧ s+i ≤ u + fst (a j))); (* s - aj <= max 0 (u - i) *)
46 match cmp_nat (fst apred) s with
48 | cmp_gt nP ⇒ match ? in False return λ_.nat with []
49 | cmp_lt nP ⇒ fst (H3 apred nP)]]
52 ∀i:nat.∃j:nat.spec i j));unfold spec in aux ⊢ %;
53 [1: apply (H2 pred nP);
54 |4: unfold X in H2; clear H4 n aux spec H3 H1 H X;
55 cases u in H2 Hs a ⊢ %; intros (a Hs H);
56 [1: left; split; [apply le_n]
57 generalize in match H;
58 generalize in match Hs;
60 [2: cases Hs; lapply (os_le_to_nat_le ?? H1);
61 apply (symmetric_eq nat O s ?).apply (le_n_O_to_eq s ?).apply (Hletin).
62 |1: intros; lapply (os_le_to_nat_le (fst (a O)) O (H2 O));
63 lapply (le_n_O_to_eq ? Hletin); assumption;]
64 |2: right; cases Hs; rewrite > (sym_plus s O); split; [apply le_S_S; apply le_O_n];
65 apply (trans_le ??? (os_le_to_nat_le ?? H1));
68 cases (aux n1) in H5 ⊢ %; intros;
69 change in match (a 〈w,H5〉) in H6 ⊢ % with (a w);
70 cases H5; clear H5; cases H7; clear H7;
71 [1: left; split; [ apply (le_S ?? H5); | assumption]
72 |3: cases (?:False); rewrite < H8 in H6; apply (not_le_Sn_n ? H6);
73 |*: cut (u ≤ S n1 ∨ S n1 < u);
74 [2,4: cases (cmp_nat u (S n1));
75 [1,4: left; apply lt_to_le; assumption
76 |2,5: rewrite > H7; left; apply le_n
77 |3,6: right; assumption ]
78 |*: cases Hcut; clear Hcut
79 [1,3: left; split; [1,3: assumption |2: symmetry; assumption]
80 cut (u = S n1); [2: apply le_to_le_to_eq; assumption ]
81 clear H7 H5 H4;rewrite > Hcut in H8:(? ? (? % ?)); clear Hcut;
82 cut (s = S (fst (a w)));
83 [2: apply le_to_le_to_eq; [2: assumption]
84 change in H8 with (s + n1 ≤ S (n1 + fst (a w)));
85 rewrite > plus_n_Sm in H8; rewrite > sym_plus in H8;
86 apply (le_plus_to_le ??? H8);]
88 change with (s = fst (a w1));
89 change in H4 with (fst (a w) < fst (a w1));
90 apply le_to_le_to_eq; [ rewrite > Hcut; assumption ]
91 apply (os_le_to_nat_le (fst (a w1)) s (H2 w1));
92 |*: right; split; try assumption;
93 [1: rewrite > sym_plus in ⊢ (? ? %);
94 rewrite < H6; apply le_plus_r; assumption;
95 |2: cases (H3 (a w) H6);
96 change with (s + S n1 ≤ u + fst (a w1));rewrite < plus_n_Sm;
97 apply (trans_le ??? (le_S_S ?? H8)); rewrite > plus_n_Sm;
98 apply (le_plus ???? (le_n ?) H9);]]]]]
99 clearbody m; unfold spec in m; clear spec;
101 let rec find i u on u : nat ≝
104 | S w ⇒ match eqb (fst (a (m i))) s with
106 | false ⇒ find (S i) w]]
109 ∀i,bound.∃j.i + bound = u → s = fst (a j));
110 [1: cases (find (S n) n2); intro; change with (s = fst (a w));
111 apply H6; rewrite < H7; simplify; apply plus_n_Sm;
112 |2: intros; rewrite > (eqb_true_to_eq ?? H5); reflexivity
113 |3: intros; rewrite > sym_plus in H5; rewrite > H5; clear H5 H4 n n1;
114 cases (m u); cases H4; clear H4; cases H5; clear H5; [assumption]
115 cases (not_le_Sn_n ? H4)]
116 clearbody find; cases (find O u);
117 exists [apply w]; intros; change with (s = fst (a j));
118 rewrite > (H4 ?); [2: reflexivity]
119 apply le_to_le_to_eq;
120 [1: apply os_le_to_nat_le;
121 apply (trans_increasing ?? H ? ? (nat_le_to_os_le ?? H5));
122 |2: apply (trans_le ? s ?);[apply os_le_to_nat_le; apply (H2 j);]
123 rewrite < (H4 ?); [2: reflexivity] apply le_n;]
126 alias symbol "pi1" = "exT fst".
127 alias symbol "leq" = "natural 'less or equal to'".
128 axiom nat_dedekind_sigma_complete_r:
129 ∀l,u:ℕ.∀a:sequence {[l,u]}.a is_decreasing →
130 ∀x.x is_infimum a → ∃i.∀j.i ≤ j → fst x = fst (a j).