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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 *)
10 (* \ / This file is distributed under the terms of the *)
11 (* v GNU General Public License Version 2 *)
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15 include "basics/types.ma".
16 include "arithmetics/nat.ma".
17 include "basics/lists/list.ma".
19 inductive t : Type[0] ≝
23 definition path ≝ list bool.
25 definition tp ≝ t × path.
27 let rec setleaf_fun (v:nat) (x:t) (p:path) on p : t × bool ≝
31 [ leaf _ ⇒ 〈leaf v,true〉
32 | node x1 x2 ⇒ 〈node x1 x2,false〉 ]
35 [ leaf n ⇒ 〈leaf n,false〉
38 let 〈x2',res〉 ≝ setleaf_fun v x2 tl in
41 let 〈x1',res〉 ≝ setleaf_fun v x1 tl in
42 〈node x1' x2, res〉 ]].
44 let rec admissible (x:t) (p:path) on p : bool ≝
51 if b then admissible x2 tl else admissible x1 tl ]].
53 definition left: ∀A:Type[0]. (bool → tp → A) → tp → A ≝
57 k (admissible t p') 〈t,p'〉.
59 definition right: ∀A:Type[0]. (bool → tp → A) → tp → A ≝
63 k (admissible t p') 〈t,p'〉.
65 definition reset: ∀A:Type[0]. (tp → A) → tp → A ≝
70 definition setleaf: ∀A:Type[0]. nat → (bool → tp → A) → tp → A ≝
73 let 〈t',res〉 ≝ setleaf_fun v t p in
76 (*****************************)
78 let rec update (A:Type[0]) (v:nat) (k: bool → tp → A) (p:path) on p:
82 [ nil ⇒ setleaf … v (λres. reset … (k res))
85 right … (λres1.update … v (λres2. k (res1 ∧ res2)) tl)
87 left … (λres1. update … v (λres2.k (res1 ∧ res2)) tl) ].
90 node (node (leaf 0) (leaf 1)) (node (leaf 2) (leaf 3)).
92 lemma test: update ? 5 (λres,x. 〈res,x〉) [false;false] 〈example,nil …〉 = ?.