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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 Functor : IUnifiable
{
public readonly Atom _name;
public readonly object[] _args;
public Functor(Atom name, object[] args)
{
if (args.Length <= 3)
{
if (args.Length == 0)
throw new Exception("For arity 0 functor, just use name as an Atom");
else if (args.Length == 1)
throw new Exception("For arity 1 functor, use Functor1");
else if (args.Length == 2)
throw new Exception("For arity 2 functor, use Functor2");
else if (args.Length == 3)
throw new Exception("For arity 3 functor, use Functor3");
else
// (This shouldn't happen, but include it for completeness.
throw new Exception("Cannot create a Functor of arity " + args.Length);
}
_name = name;
_args = args;
}
public Functor(string name, object[] args)
: this(Atom.a(name), args)
{
}
/// <summary>
/// Return an Atom, Functor1, Functor2, Functor3 or Functor depending on the
/// length of args.
/// Note that this is different than the Functor constructor which requires
/// the length of args to be greater than 3.
/// </summary>
/// <param name="name"></param>
/// <param name="args"></param>
/// <returns></returns>
public static object make(Atom name, object[] args)
{
if (args.Length <= 0)
return name;
else if (args.Length == 1)
return new Functor1(name, args[0]);
else if (args.Length == 2)
return new Functor2(name, args[0], args[1]);
else if (args.Length == 3)
return new Functor3(name, args[0], args[1], args[2]);
else
return new Functor(name, args);
}
/// <summary>
/// Call the main make, first converting name to an Atom.
/// </summary>
/// <param name="name"></param>
/// <param name="args"></param>
/// <returns></returns>
public static object make(string name, object[] args)
{
return make(Atom.a(name), args);
}
/// <summary>
/// If arg is another Functor, 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).
/// </summary>
/// <param name="arg"></param>
/// <returns></returns>
public IEnumerable<bool> unify(object arg)
{
arg = YP.getValue(arg);
if (arg is Functor)
{
Functor argFunctor = (Functor)arg;
if (_name.Equals(argFunctor._name))
return YP.unifyArrays(_args, argFunctor._args);
else
return YP.fail();
}
else if (arg is Variable)
return ((Variable)arg).unify(this);
else
return YP.fail();
}
public override string ToString()
{
string result = _name + "(" + YP.getValue(_args[0]);
for (int i = 1; i < _args.Length; ++i)
result += ", " + YP.getValue(_args[i]);
result += ")";
return result;
}
public bool termEqual(object term)
{
term = YP.getValue(term);
if (term is Functor)
{
Functor termFunctor = (Functor)term;
if (_name.Equals(termFunctor._name) && _args.Length == termFunctor._args.Length)
{
for (int i = 0; i < _args.Length; ++i)
{
if (!YP.termEqual(_args[i], termFunctor._args[i]))
return false;
}
return true;
}
}
return false;
}
public bool lessThan(Functor functor)
{
// Do the equal check first since it is faster.
if (!_name.Equals(functor._name))
return _name.lessThan(functor._name);
if (_args.Length != functor._args.Length)
return _args.Length < functor._args.Length;
for (int i = 0; i < _args.Length; ++i)
{
if (!YP.termEqual(_args[i], functor._args[i]))
return YP.termLessThan(_args[i], functor._args[i]);
}
return false;
}
public bool ground()
{
for (int i = 0; i < _args.Length; ++i)
{
if (!YP.ground(_args[i]))
return false;
}
return true;
}
public void addUniqueVariables(List<Variable> variableSet)
{
for (int i = 0; i < _args.Length; ++i)
YP.addUniqueVariables(_args[i], variableSet);
}
public object makeCopy(Variable.CopyStore copyStore)
{
object[] argsCopy = new object[_args.Length];
for (int i = 0; i < _args.Length; ++i)
argsCopy[i] = YP.makeCopy(_args[i], copyStore);
return new Functor(_name, argsCopy);
}
}
}
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