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/*
* Copyright (C) 2007-2008, Jeff Thompson
*
* All rights reserved.
*
* Redistribution and use in source and binary forms, with or without
* modification, are permitted provided that the following conditions are met:
*
* * Redistributions of source code must retain the above copyright
* notice, this list of conditions and the following disclaimer.
* * Redistributions in binary form must reproduce the above copyright
* notice, this list of conditions and the following disclaimer in the
* documentation and/or other materials provided with the distribution.
* * Neither the name of the copyright holder nor the names of its contributors
* may be used to endorse or promote products derived from this software
* without specific prior written permission.
*
* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
* CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
* EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
* PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
* PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
* NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
* SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
*/
using System;
using System.Collections;
using System.Collections.Generic;
namespace OpenSim.Region.ScriptEngine.Shared.YieldProlog
{
/// <summary>
/// A BagofAnswers holds answers for bagof and setof.
/// </summary>
public class BagofAnswers
{
private object _template;
private Variable[] _freeVariables;
private Dictionary<object[], List<object>> _bagForFreeVariables;
private List<object> _findallBagArray;
private static TermArrayEqualityComparer _termArrayEqualityComparer =
new TermArrayEqualityComparer();
/// <summary>
/// To get the free variables, split off any existential qualifiers from Goal such as the X in
/// "X ^ f(Y)", get the set of unbound variables in Goal that are not qualifiers, then remove
/// the unbound variables that are qualifiers as well as the unbound variables in Template.
/// </summary>
/// <param name="Template"></param>
/// <param name="Goal"></param>
public BagofAnswers(object Template, object Goal)
{
_template = Template;
// First get the set of variables that are not free variables.
List<Variable> variableSet = new List<Variable>();
YP.addUniqueVariables(Template, variableSet);
object UnqualifiedGoal = YP.getValue(Goal);
while (UnqualifiedGoal is Functor2 && ((Functor2)UnqualifiedGoal)._name == Atom.HAT)
{
YP.addUniqueVariables(((Functor2)UnqualifiedGoal)._arg1, variableSet);
UnqualifiedGoal = YP.getValue(((Functor2)UnqualifiedGoal)._arg2);
}
// Remember how many non-free variables there are so we can find the unique free variables
// that are added.
int nNonFreeVariables = variableSet.Count;
YP.addUniqueVariables(UnqualifiedGoal, variableSet);
int nFreeVariables = variableSet.Count - nNonFreeVariables;
if (nFreeVariables == 0)
{
// There were no free variables added, so we won't waste time with _bagForFreeVariables.
_freeVariables = null;
_findallBagArray = new List<object>();
}
else
{
// Copy the free variables.
_freeVariables = new Variable[nFreeVariables];
for (int i = 0; i < nFreeVariables; ++i)
_freeVariables[i] = variableSet[i + nNonFreeVariables];
_bagForFreeVariables = new Dictionary<object[], List<object>>(_termArrayEqualityComparer);
}
}
public void add()
{
if (_freeVariables == null)
// The goal has bound the values in _template but we don't bother with _freeVariables.
_findallBagArray.Add(YP.makeCopy(_template, new Variable.CopyStore()));
else
{
// The goal has bound the values in _template and _freeVariables.
// Find the entry for this set of _freeVariables values.
object[] freeVariableValues = new object[_freeVariables.Length];
for (int i = 0; i < _freeVariables.Length; ++i)
freeVariableValues[i] = YP.getValue(_freeVariables[i]);
List<object> bagArray;
if (!_bagForFreeVariables.TryGetValue(freeVariableValues, out bagArray))
{
bagArray = new List<object>();
_bagForFreeVariables[freeVariableValues] = bagArray;
}
// Now copy the template and add to the bag for the freeVariables values.
bagArray.Add(YP.makeCopy(_template, new Variable.CopyStore()));
}
}
/// <summary>
/// For each result, unify the _freeVariables and unify bagArrayVariable with the associated bag.
/// </summary>
/// <param name="bagArrayVariable">this is unified with the List<object> of matches for template that
/// corresponds to the bindings for freeVariables. Be very careful: this does not unify with a Prolog
/// list.</param>
/// <returns></returns>
public IEnumerable<bool> resultArray(Variable bagArrayVariable)
{
if (_freeVariables == null)
{
// No unbound free variables, so we only filled one bag. If empty, bagof fails.
if (_findallBagArray.Count > 0)
{
foreach (bool l1 in bagArrayVariable.unify(_findallBagArray))
yield return false;
}
}
else
{
foreach (KeyValuePair<object[], List<object>> valuesAndBag in _bagForFreeVariables)
{
foreach (bool l1 in YP.unifyArrays(_freeVariables, valuesAndBag.Key))
{
foreach (bool l2 in bagArrayVariable.unify(valuesAndBag.Value))
yield return false;
}
// Debug: Should we free memory of the answers already returned?
}
}
}
/// <summary>
/// For each result, unify the _freeVariables and unify Bag with the associated bag.
/// </summary>
/// <param name="Bag"></param>
/// <returns></returns>
public IEnumerable<bool> result(object Bag)
{
Variable bagArrayVariable = new Variable();
foreach (bool l1 in resultArray(bagArrayVariable))
{
foreach (bool l2 in YP.unify(Bag, ListPair.make((List<object>)bagArrayVariable.getValue())))
yield return false;
}
}
/// <summary>
/// For each result, unify the _freeVariables and unify Bag with the associated bag which is sorted
/// with duplicates removed, as in setof.
/// </summary>
/// <param name="Bag"></param>
/// <returns></returns>
public IEnumerable<bool> resultSet(object Bag)
{
Variable bagArrayVariable = new Variable();
foreach (bool l1 in resultArray(bagArrayVariable))
{
List<object> bagArray = (List<object>)bagArrayVariable.getValue();
YP.sortArray(bagArray);
foreach (bool l2 in YP.unify(Bag, ListPair.makeWithoutRepeatedTerms(bagArray)))
yield return false;
}
}
public static IEnumerable<bool> bagofArray
(object Template, object Goal, IEnumerable<bool> goalIterator, Variable bagArrayVariable)
{
BagofAnswers bagOfAnswers = new BagofAnswers(Template, Goal);
foreach (bool l1 in goalIterator)
bagOfAnswers.add();
return bagOfAnswers.resultArray(bagArrayVariable);
}
public static IEnumerable<bool> bagof
(object Template, object Goal, IEnumerable<bool> goalIterator, object Bag)
{
BagofAnswers bagOfAnswers = new BagofAnswers(Template, Goal);
foreach (bool l1 in goalIterator)
bagOfAnswers.add();
return bagOfAnswers.result(Bag);
}
public static IEnumerable<bool> setof
(object Template, object Goal, IEnumerable<bool> goalIterator, object Bag)
{
BagofAnswers bagOfAnswers = new BagofAnswers(Template, Goal);
foreach (bool l1 in goalIterator)
bagOfAnswers.add();
return bagOfAnswers.resultSet(Bag);
}
/// <summary>
/// A TermArrayEqualityComparer implements IEqualityComparer to compare two object arrays using YP.termEqual.
/// </summary>
private class TermArrayEqualityComparer : IEqualityComparer<object[]>
{
public bool Equals(object[] array1, object[] array2)
{
if (array1.Length != array2.Length)
return false;
for (int i = 0; i < array1.Length; ++i)
{
if (!YP.termEqual(array1[i], array2[i]))
return false;
}
return true;
}
public int GetHashCode(object[] array)
{
int hashCode = 0;
for (int i = 0; i < array.Length; ++i)
hashCode ^= array[i].GetHashCode();
return hashCode;
}
}
}
}
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