/YieldProlog/Modules/Functor2.cs

/*

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 */



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;

        }

    }

}