public static SimulationPath <A, S> RunSimulation(PDA <A, S> pda, A[] word) { var acceptanceResult = pda.AcceptsWord(word); if (!acceptanceResult.Accepts()) { throw new NoAcceptanceException("the pda does not accept the word, therefore, a simulation is not possible"); } var initialNode = SimulationNode <A, S> .InitialNode( new Configuration <A, S>(pda.InitialState, new Word <A>(word), CurrentStack <S> .WithSingleSymbol(pda.FirstStackSymbol)), pda.AcceptanceCondition); var frontChain = new List <SimulationNode <A, S> > { initialNode }; while (frontChain.Count() > 0) { var nodesAcceptedWord = frontChain.Where(node => node.HasAcceptedWord).ToList(); if (nodesAcceptedWord.Count() > 0) { return(SimulationPathFromFinalNode(nodesAcceptedWord.First())); } foreach (var node in frontChain) { node.DoStep(); } frontChain = frontChain.SelectMany(node => node.Children).ToList(); } throw new InvalidOperationException("the given pda does not accept the word, therefore a simulation is not possible"); }
//FIXME: create own subclass class for derivation start node /// <summary> /// converts a derivation of a word in a CFG in 2NF, that was originally created from a PDA, back to a path in this PDA; /// this path is generated according to the converting-algorithm of a PDA to a CFG implemented in <see cref="PDAToCFGConverter{A, S}"/>; /// if this method is called on a CFG that does not fulfill the described conditions, it produces not useful result /// </summary> /// <param name="pda">pda</param> /// <param name="startSymbol">start symbol of the cfg</param> /// <param name="word">word of the derivation</param> /// <returns></returns> public SimulationPath <A, char> ConvertToPDASimulationPath(PDA <A, char> pda, GrammarSymbol startSymbol, A[] word) { Assertion.Assert(Symbol == startSymbol, "this method should only be called on the start node; FIXME to make it only availabe there"); Assertion.Assert(productionFromHere.Rhs.Count() == 1, "the first production should only lead to one element"); Assertion.Assert(children.Count() == 1, "the start symbol should only have one child"); var symbol = productionFromHere.Rhs[0].Name; var splitted = PDAToCFGConverter <A, char> .SplitNonTerminalId(symbol); var firstNode = Node <A, char> .InitialNode(new Configuration <A, char>(pda.States[splitted.Item1], new Word <A>(word), CurrentStack <char> .WithSingleSymbol(splitted.Item2))); var nodes = new List <Node <A, char> >() { firstNode }; children.First().ConvertToPDASimulationPath(nodes, pda); return(new SimulationPath <A, char>(nodes)); }