1 (**************************************************************************)
4 (* ||A|| A project by Andrea Asperti *)
6 (* ||I|| Developers: *)
7 (* ||T|| The HELM team. *)
8 (* ||A|| http://helm.cs.unibo.it *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
13 (**************************************************************************)
15 include "list/list.ma".
17 interpretation "list nth" 'nth = (nth _).
18 interpretation "list nth" 'nth_appl l d i = (nth _ l d i).
19 notation "\nth" with precedence 90 for @{'nth}.
20 notation < "\nth \nbsp term 90 l \nbsp term 90 d \nbsp term 90 i"
21 with precedence 69 for @{'nth_appl $l $d $i}.
23 definition make_list ≝
25 let rec make_list (n:nat) on n ≝
26 match n with [ O ⇒ nil ? | S m ⇒ def m :: make_list m]
29 interpretation "\mk_list appl" 'mk_list_appl f n = (make_list _ f n).
30 interpretation "\mk_list" 'mk_list = (make_list _).
31 notation "\mk_list" with precedence 90 for @{'mk_list}.
32 notation < "\mk_list \nbsp term 90 f \nbsp term 90 n"
33 with precedence 69 for @{'mk_list_appl $f $n}.
35 notation "\len" with precedence 90 for @{'len}.
36 interpretation "len" 'len = (length _).
37 notation < "\len \nbsp term 90 l" with precedence 69 for @{'len_appl $l}.
38 interpretation "len appl" 'len_appl l = (length _ l).
40 lemma len_mk_list : ∀T:Type.∀f:nat→T.∀n.\len (\mk_list f n) = n.
41 intros; elim n; [reflexivity] simplify; rewrite > H; reflexivity;
46 rel_op :2> rel_T → rel_T → Prop
49 record trans_rel : Type ≝ {
51 o_tra : ∀x,y,z: o_rel.o_rel x y → o_rel y z → o_rel x z
54 lemma trans: ∀r:trans_rel.∀x,y,z:r.r x y → r y z → r x z.
58 inductive sorted (lt : trans_rel): list (rel_T lt) → Prop ≝
59 | sorted_nil : sorted lt []
60 | sorted_one : ∀x. sorted lt [x]
61 | sorted_cons : ∀x,y,tl. lt x y → sorted lt (y::tl) → sorted lt (x::y::tl).
63 lemma nth_nil: ∀T,i.∀def:T. \nth [] def i = def.
64 intros; elim i; simplify; [reflexivity;] assumption; qed.
66 lemma len_append: ∀T:Type.∀l1,l2:list T. \len (l1@l2) = \len l1 + \len l2.
67 intros; elim l1; [reflexivity] simplify; rewrite < H; reflexivity;
70 inductive non_empty_list (A:Type) : list A → Type :=
71 | show_head: ∀x,l. non_empty_list A (x::l).
73 lemma len_gt_non_empty :
74 ∀T.∀l:list T.O < \len l → non_empty_list T l.
75 intros; cases l in H; [intros; cases (not_le_Sn_O ? H);] intros; constructor 1;
78 lemma sorted_tail: ∀r,x,l.sorted r (x::l) → sorted r l.
79 intros; inversion H; intros; [destruct H1;|destruct H1;constructor 1;]
80 destruct H4; assumption;
83 lemma sorted_skip: ∀r,x,y,l. sorted r (x::y::l) → sorted r (x::l).
84 intros (r x y l H1); inversion H1; intros; [1,2: destruct H]
85 destruct H4; inversion H2; intros; [destruct H4]
86 [1: destruct H4; constructor 2;
87 |2: destruct H7; constructor 3; [ apply (o_tra ? ??? H H4);]
88 apply (sorted_tail ??? H2);]
91 lemma sorted_tail_bigger : ∀r,x,l,d.sorted r (x::l) → ∀i. i < \len l → r x (\nth l d i).
92 intros 4; elim l; [ cases (not_le_Sn_O i H1);]
94 [2: intros; apply (H ? n);[apply (sorted_skip ???? H1)|apply le_S_S_to_le; apply H2]
95 |1: intros; inversion H1; intros; [1,2: destruct H3]
96 destruct H6; simplify; assumption;]
99 lemma all_bases_positive : ∀f:q_f.∀i. OQ < nth_base (bars f) (S i).
100 intro f; generalize in match (bars_begin_OQ f); generalize in match (bars_sorted f);
101 cases (bars_not_nil f); intros;
102 cases (cmp_nat i (len l));
103 [1: lapply (sorted_tail_bigger ?? H ? H2) as K; simplify in H1;
104 rewrite > H1 in K; apply K;
105 |2: rewrite > H2; simplify; elim l; simplify; [apply (q_pos_OQ one)]
107 |3: simplify; elim l in i H2;[simplify; rewrite > nth_nil; apply (q_pos_OQ one)]
108 cases n in H3; intros; [cases (not_le_Sn_O ? H3)] apply (H2 n1);
109 apply (le_S_S_to_le ?? H3);]
112 lemma lt_n_plus_n_Sm : ∀n,m:nat.n < n + S m.
113 intros; rewrite > sym_plus; apply (le_S_S n (m+n)); apply (le_plus_n m n); qed.
115 lemma nth_concat_lt_len:
116 ∀T:Type.∀l1,l2:list T.∀def.∀i.i < len l1 → nth (l1@l2) def i = nth l1 def i.
117 intros 4; elim l1; [cases (not_le_Sn_O ? H)] cases i in H H1; simplify; intros;
118 [reflexivity| rewrite < H;[reflexivity] apply le_S_S_to_le; apply H1]
121 lemma nth_concat_ge_len:
122 ∀T:Type.∀l1,l2:list T.∀def.∀i.
123 len l1 ≤ i → nth (l1@l2) def i = nth l2 def (i - len l1).
124 intros 4; elim l1; [ rewrite < minus_n_O; reflexivity]
125 cases i in H1; simplify; intros; [cases (not_le_Sn_O ? H1)]
126 apply H; apply le_S_S_to_le; apply H1;
130 ∀T:Type.∀l1,l2:list T.∀def,x.
131 nth (l1@x::l2) def (len l1) = x.
132 intros 2; elim l1;[reflexivity] simplify; apply H; qed.
134 lemma all_bigger_can_concat_bigger:
136 (∀i.i< len l1 → nth_base l1 i < \fst b) →
137 (∀i.i< len l2 → \fst b ≤ nth_base l2 i) →
138 (∀i.i< len l1 → start ≤ i → x ≤ nth_base l1 i) →
139 start ≤ n → n < len (l1@b::l2) → x ≤ \fst b → x ≤ nth_base (l1@b::l2) n.
140 intros; cases (cmp_nat n (len l1));
141 [1: unfold nth_base; rewrite > (nth_concat_lt_len ????? H6);
142 apply (H2 n); assumption;
143 |2: rewrite > H6; unfold nth_base; rewrite > nth_len; assumption;
144 |3: unfold nth_base; rewrite > nth_concat_ge_len; [2: apply lt_to_le; assumption]
145 rewrite > len_concat in H4; simplify in H4; rewrite < plus_n_Sm in H4;
146 lapply linear le_S_S_to_le to H4 as K; rewrite > sym_plus in K;
147 lapply linear le_plus_to_minus to K as X;
148 generalize in match X; generalize in match (n - len l1); intro W; cases W; clear W X;
149 [intros; assumption] intros;
150 apply (q_le_trans ??? H5); apply (H1 n1); assumption;]
153 lemma sorted_head_smaller:
154 ∀l,p. sorted (p::l) → ∀i.i < len l → \fst p < nth_base l i.
155 intro l; elim l; intros; [cases (not_le_Sn_O ? H1)] cases i in H2; simplify; intros;
156 [1: inversion H1; [1,2: simplify; intros; destruct H3] intros; destruct H6; assumption;
157 |2: apply (H p ? n ?); [apply (sorted_skip ??? H1)] apply le_S_S_to_le; apply H2]