AIMA.Core.Logic.Propositional.Algorithms.PLFCEntails.HornClause.HornClause C# (CSharp) Method

            public HornClause(Sentence sentence, PLFCEntails plfcEntails)
            {
                this.plfcEntails = plfcEntails;
                if (sentence is Symbol)
                {
                    _head = (Symbol)sentence;
                    plfcEntails.agenda.Push(_head);
                    premiseSymbols = new List<Symbol>();
                    plfcEntails.count.Add(this, 0);
                    plfcEntails._inferred.Add(_head, false);
                }
                else if (!isImpliedSentence(sentence))
                {
                    throw new ApplicationException("Sentence " + sentence
                            + " is not a horn clause");

                }
                else
                {
                    BinarySentence bs = (BinarySentence)sentence;
                    _head = (Symbol)bs.getSecond();
                    if (plfcEntails._inferred.ContainsKey(_head))
                    {
                        plfcEntails._inferred[_head] = false;
                    }
                    else
                    {
                        plfcEntails._inferred.Add(_head, false);
                    }
                    List<Symbol> symbolsInPremise = new SymbolCollector()
                            .getSymbolsIn(bs.getFirst());
                    foreach(Symbol s in symbolsInPremise)
                    {
                        plfcEntails._inferred.Add(s, false);
                    }
                    premiseSymbols = symbolsInPremise;
                    plfcEntails.count.Add(this, premiseSymbols.Count);
                }

            }