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4 (* ||A|| A project by Andrea Asperti *)
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7 (* ||T|| The HELM team. *)
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15 set "baseuri" "cic:/matita/list/sort/".
17 include "datatypes/bool.ma".
18 include "datatypes/constructors.ma".
19 include "list/list.ma".
21 let rec mem (A:Set) (eq: A → A → bool) x (l: list A) on l ≝
27 | false ⇒ mem A eq x l'
31 let rec ordered (A:Set) (le: A → A → bool) (l: list A) on l ≝
38 le x y \land ordered A le l'
42 let rec insert (A:Set) (le: A → A → bool) x (l: list A) on l ≝
48 | false ⇒ he::(insert A le x l')
53 ∀A:Set. ∀le: A → A → bool. ∀x:A.
55 ∀l:list A. P (insert A le x l).
56 intros (A le x P H l).
58 let rec insert_ind (l: list A) ≝
59 match l in list return λl.P (insert A le x l) with
62 match le x he return λb.P (match b with [ true ⇒ x::he::l' | false ⇒ he::(insert A le x l') ]) with
63 [ true ⇒ (H2 : P (x::he::l'))
64 | false ⇒ (? : P (he::(insert A le x l')))
72 let rec insertionsort (A:Set) (le: A → A → bool) (l: list A) on l ≝
76 let l'' ≝ insertionsort A le l' in
80 lemma ordered_injective:
81 ∀ A:Set. ∀ le:A → A → bool.
84 \to ordered A le (tail A l) = true.
87 [ simplify; reflexivity;
89 generalize in match H1;
92 [ simplify; reflexivity;
93 | cut ((le s s1 \land ordered A le (s1::l2)) = true);
94 [ generalize in match Hcut;
98 fold simplify (ordered ? le (s1::l2));
103 apply (not_eq_true_false);
115 \forall A:Set. \forall le:A\to A\to bool.
116 (\forall a,b:A. le a b = false \to le b a = true) \to
117 \forall l:list A. \forall x:A.
118 ordered A le l = true \to ordered A le (insert A le x l) = true.
119 intros 5 (A le H l x).
121 let rec insert_ind (l: list A) \def
125 l = li → ordered ? le li = true →
126 ordered ? le (insert A le x li) = true
128 [ nil ⇒ (? : l = [] → ordered ? le [] = true → ordered ? le [x] = true)
132 λb. le x he = b → l = he::l' →
133 ordered ? le (he::l') = true → ordered ? le
136 | false ⇒ he::(insert A le x l') ]) = true
142 ordered ? le (he::l') = true →
143 ordered ? le (x::he::l') = true)
145 let res ≝ insert_ind l' in
147 le x he = false → l = he::l' →
148 ordered ? le (he::l') = true →
149 ordered ? le (he::(insert ? le x l')) = true)
151 (refl_eq ? (le x he))
152 ] (refl_eq ? l) in insert_ind l);
155 [ rewrite > insert_ind;
156 [ generalize in match (H ? ? H1); clear H1; intro;
157 generalize in match H3; clear H3;
161 | elim (le x s); simplify;
165 rewrite > (andb_true_true ? ? H3);
170 | apply (ordered_injective ? ? ? H3)
179 theorem insertionsort_sorted:
181 ∀le:A → A → bool.∀eq:A → A → bool.
182 (∀a,b:A. le a b = false → le b a = true) \to
184 ordered A le (insertionsort A le l) = true.
185 intros 5 (A le eq le_tot l).
189 | apply (insert_sorted A le le_tot (insertionsort A le l1) s);