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1 (**************************************************************************)
2 (*       ___                                                              *)
3 (*      ||M||                                                             *)
4 (*      ||A||       A project by Andrea Asperti                           *)
5 (*      ||T||                                                             *)
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10 (*       \ /        This file is distributed under the terms of the       *)
11 (*        v         GNU General Public License Version 2                  *)
12 (*                                                                        *)
13 (**************************************************************************)
14
15 include "pointer_list.ma".
16
17 (* POINTER TREE *************************************************************)
18
19 (* Policy: pointer tree metavariables: P, Q *)
20 (* Note: this is a binary tree on pointer sequences *)
21 inductive ptrt: Type[0] ≝
22 | tnil : ptrt
23 | tcons: ptrl → ptrt → ptrt → ptrt
24 .
25
26 let rec length (P:ptrt) on P ≝ match P with
27 [ tnil          ⇒ 0
28 | tcons s Q1 Q2 ⇒ length Q2 + length Q1 + |s|
29 ].
30
31 interpretation "pointer tree length" 'card P = (length P).