1% ---------------------------------------------------------------------- 2% BEGIN LICENSE BLOCK 3% Version: CMPL 1.1 4% 5% The contents of this file are subject to the Cisco-style Mozilla Public 6% License Version 1.1 (the "License"); you may not use this file except 7% in compliance with the License. You may obtain a copy of the License 8% at www.eclipse-clp.org/license. 9% 10% Software distributed under the License is distributed on an "AS IS" 11% basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See 12% the License for the specific language governing rights and limitations 13% under the License. 14% 15% The Original Code is The ECLiPSe Constraint Logic Programming System. 16% The Initial Developer of the Original Code is Cisco Systems, Inc. 17% Portions created by the Initial Developer are 18% Copyright (C) 1991-2006 Cisco Systems, Inc. All Rights Reserved. 19% 20% Contributor(s): ECRC GmbH 21% Contributor(s): IC-Parc, Imperal College London 22% 23% END LICENSE BLOCK 24% 25% System: ECLiPSe Constraint Logic Programming System 26% Version: $Id: numbervars.pl,v 1.3 2010/03/15 01:55:15 jschimpf Exp $ 27% ---------------------------------------------------------------------- 28 29% 30% SEPIA PROLOG LIBRARY MODULE 31% 32% IDENTIFICATION: numbervars.pl 33% 34% AUTHOR: Joachim Schimpf 35% 36% CONTENTS: numbervars/3 37% 38 39:- module(numbervars). 40 41:- comment(categories, ["Algorithms","Compatibility"]). 42:- comment(summary, "C-Prolog style numbervars predicate"). 43:- comment(author, "Joachim Schimpf, ECRC Munich"). 44:- comment(copyright, "Cisco Systems, Inc"). 45:- comment(date, "$Date: 2010/03/15 01:55:15 $"). 46:- comment(desc, html(" 47 Implements the numbervars(Term, From, To) predicate of C-Prolog. Term 48 is any term, From and To are integer numbers. All variables in Term 49 are instantiated to terms of the form 50 <PRE> 51 $VAR(N) 52 </PRE> 53 where N is an integer number. The first encountered variable will be 54 coded by the number From, on exit To is instantiated to the next 55 unused number. 56 <P> 57 This predicate can thus be used to encode nonground term using a 58 ground representation. Note that metaterms can be used for the same 59 purpose, but their use is both more efficient and more general, 60 because the variables are not actually instantiated and so they can be 61 used again as variables when needed. 62 ")). 63 64:- export numbervars/3. 65 66 67numbervars('$VAR'(N), N, N1) :- !, 68 N1 is N + 1. 69numbervars(Term, N, Next) :- 70 arity(Term, Arity), 71 numbervars(0, Arity, Term, N, Next). 72 73numbervars(Arity, Arity, _, N, Next) :- !, N = Next. 74numbervars(I, Arity, Term, N0, N) :- 75 I1 is I + 1, 76 arg(I1, Term, Arg), 77 numbervars(Arg, N0, N1), 78 numbervars(I1, Arity, Term, N1, N). 79 80