jpl stuff
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172
LGPL/JPL/java/jpl/Util.java
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172
LGPL/JPL/java/jpl/Util.java
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//tabstop=4
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//*****************************************************************************/
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// Project: jpl
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//
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// File: $Id: Util.java,v 1.1 2004-08-27 20:27:56 vsc Exp $
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// Date: $Date: 2004-08-27 20:27:56 $
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// Author: Fred Dushin <fadushin@syr.edu>
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//
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//
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// Description:
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//
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//
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// -------------------------------------------------------------------------
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// Copyright (c) 2004 Paul Singleton
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// Copyright (c) 1998 Fred Dushin
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// All rights reserved.
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//
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// This library is free software; you can redistribute it and/or
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// modify it under the terms of the GNU Library Public License
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// as published by the Free Software Foundation; either version 2
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// of the License, or (at your option) any later version.
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//
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// This library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Library Public License for more details.
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//*****************************************************************************/
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package jpl;
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import java.util.Hashtable;
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import java.util.Map;
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//----------------------------------------------------------------------/
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// Util
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/**
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* This class provides a bunch of static utility methods for the JPL
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* High-Level Interface.
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*
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* <hr><i>
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* Copyright (C) 2004 Paul Singleton<p>
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* Copyright (C) 1998 Fred Dushin<p>
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*
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* This library is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Library Public License
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* as published by the Free Software Foundation; either version 2
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* of the License, or (at your option) any later version.<p>
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*
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* This library is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Library Public License for more details.<p>
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* </i><hr>
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* @author Fred Dushin <fadushin@syr.edu>
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* @version $Revision: 1.1 $
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*/
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public final class Util {
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//------------------------------------------------------------------/
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// termArrayToList
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/**
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* Converts an array of Terms to a JPL representation of a Prolog list of terms
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* whose members correspond to the respective array elements.
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*
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* @param terms An array of Term
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* @return Term a list of the array elements
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*/
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public static Term termArrayToList(Term[] terms) {
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Term list = new Atom("[]");
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for (int i = terms.length - 1; i >= 0; --i) {
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list = new Compound(".", new Term[] { terms[i], list });
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}
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return list;
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}
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/**
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* Converts a solution hashtable to an array of Terms.
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*
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* @param varnames_to_Terms A Map from variable names to Terms
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* @return Term[] An array of the Terms to which successive variables are bound
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*/
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public static Term[] bindingsToTermArray(Map varnames_to_Terms) {
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Term[] ts = new Term[varnames_to_Terms.size()];
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for (java.util.Iterator i = varnames_to_Terms.keySet().iterator(); i.hasNext();) {
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Variable k = (Variable) i.next();
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ts[k.index] = (Term) (varnames_to_Terms.get(k));
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}
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return ts;
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}
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//------------------------------------------------------------------/
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// toString
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/**
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* Converts a substitution, in the form of a Map from variable names to Terms, to a String.
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*
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* @param varnames_to_Terms A Map from variable names to Terms.
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* @return String A String representation of the variable bindings
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*/
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public static String toString(Map varnames_to_Terms) {
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if (varnames_to_Terms == null) {
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return "[no solution]";
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}
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java.util.Iterator varnames = varnames_to_Terms.keySet().iterator();
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String s = "Bindings: ";
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while (varnames.hasNext()) {
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String varname = (String) varnames.next();
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s += varname + "=" + varnames_to_Terms.get(varname).toString() + "; ";
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}
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return s;
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}
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//------------------------------------------------------------------/
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// namevarsToMap
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/**
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* Converts a (JPL) list of Name=Var pairs (as yielded by atom_to_term/3)
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* to a Map from Prolog variables (necessarily in term_t holders) to named JPL Variables
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*
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* @param nvs A JPL list of Name=Var pairs (as yielded by atom_to_term/3)
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* @return Map A Map from Prolog variables (necessarily in term_t holders) to named JPL Variables
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*/
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public static Map namevarsToMap(Term nvs) {
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try {
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Map vars_to_Vars = new Hashtable();
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/*
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while (nvs.hasFunctor(".", 2) && ((Compound) nvs).arg(1).hasFunctor("=", 2)) {
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Atom name = (Atom) ((Compound) ((Compound) nvs).arg(1)).arg(1); // get the Name of the =/2 pair
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Variable var = (Variable) ((Compound) ((Compound) nvs).arg(1)).arg(2); // get the Var of the =/2 pair
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vars_to_Vars.put(var.term_, new Variable(name.name())); // map the Prolog variable to a new, named Variable
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nvs = ((Compound) nvs).arg(2); // advance to next list cell
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}
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*/
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while (nvs.hasFunctor(".", 2) && nvs.arg(1).hasFunctor("=", 2)) {
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// the cast to Variable is necessary to access the (protected) .term_ field
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vars_to_Vars.put(((Variable)nvs.arg(1).arg(2)).term_, new Variable(nvs.arg(1).arg(1).name())); // map the Prolog variable to a new, named Variable
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nvs = nvs.arg(2); // advance to next list cell
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}
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// maybe oughta check that nvs is [] ?
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return vars_to_Vars;
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} catch (java.lang.ClassCastException e) { // nvs is not of the expected structure
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return null;
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}
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}
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//------------------------------------------------------------------/
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// textToTerm
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/**
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* Converts a Prolog source text to a corresponding JPL Term
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* (in which each Variable has the appropriate name from the source text).
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* Throws PrologException containing error(syntax_error(_),_) if text is invalid.
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*
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* @param text A Prolog source text denoting a term
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* @return Term a JPL Term equivalent to the given source text
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*/
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public static Term textToTerm(String text) {
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// it might be better to use PL_chars_to_term()
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Query q = new Query(new Compound("atom_to_term", new Term[] { new Atom(text), new Variable("Term"), new Variable("NVdict")}));
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q.open();
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Map s = q.getSubstWithNameVars();
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if (s != null) {
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q.close();
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return (Term) s.get("Term");
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} else {
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return null;
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}
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}
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}
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