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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.Generic;
namespace OpenSim.Region.ScriptEngine.Shared.YieldProlog
{
public class Functor2 : IUnifiable
{
public readonly Atom _name;
public readonly object _arg1;
public readonly object _arg2;
public Functor2(Atom name, object arg1, object arg2)
{
_name = name;
_arg1 = arg1;
_arg2 = arg2;
}
public Functor2(string name, object arg1, object arg2)
: this(Atom.a(name), arg1, arg2)
{
}
// disable warning on l1, don't see how we can
// code this differently
#pragma warning disable 0168, 0219
/// If arg is another Functor2, then succeed (yield once) if this and arg have the
/// same name and all functor args unify, otherwise fail (don't yield).
/// If arg is a Variable, then call its unify to unify with this.
/// Otherwise fail (don't yield).
public IEnumerable<bool> unify(object arg)
{
arg = YP.getValue(arg);
if (arg is Functor2)
{
Functor2 argFunctor = (Functor2)arg;
if (_name.Equals(argFunctor._name))
{
foreach (bool l1 in YP.unify(_arg1, argFunctor._arg1))
{
foreach (bool l2 in YP.unify(_arg2, argFunctor._arg2))
yield return false;
}
}
}
else if (arg is Variable)
{
foreach (bool l1 in ((Variable)arg).unify(this))
yield return false;
}
}
#pragma warning restore 0168, 0219
public override string ToString()
{
if (_name == Atom.DOT)
return listPairToString(this);
else
return _name + "(" + YP.getValue(_arg1) + ", " + YP.getValue(_arg2) + ")";
}
public bool termEqual(object term)
{
term = YP.getValue(term);
if (term is Functor2)
{
Functor2 termFunctor = (Functor2)term;
return _name.Equals(termFunctor._name) && YP.termEqual(_arg1, termFunctor._arg1)
&& YP.termEqual(_arg2, termFunctor._arg2);
}
return false;
}
public bool lessThan(Functor2 functor)
{
// Do the equal check first since it is faster.
if (!_name.Equals(functor._name))
return _name.lessThan(functor._name);
if (!YP.termEqual(_arg1, functor._arg1))
return YP.termLessThan(_arg1, functor._arg1);
return YP.termLessThan(_arg2, functor._arg2);
}
public bool ground()
{
return YP.ground(_arg1) && YP.ground(_arg2);
}
public void addUniqueVariables(List<Variable> variableSet)
{
YP.addUniqueVariables(_arg1, variableSet);
YP.addUniqueVariables(_arg2, variableSet);
}
public object makeCopy(Variable.CopyStore copyStore)
{
return new Functor2(_name, YP.makeCopy(_arg1, copyStore),
YP.makeCopy(_arg2, copyStore));
}
private static string listPairToString(Functor2 listPair)
{
string result = "[";
while (true)
{
object head = YP.getValue(listPair._arg1);
object tail = YP.getValue(listPair._arg2);
if (tail == (object)Atom.NIL)
{
result += head;
break;
}
else if (tail is Functor2 && ((Functor2)tail)._name == Atom.DOT)
{
result += head + ", ";
listPair = (Functor2)tail;
// Loop again.
}
else
{
// The list is not terminated with NIL.
result += head + "|" + tail;
break;
}
}
result += "]";
return result;
}
}
}
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