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));
}
