public (string, string) ConvertNFAToRegEx()
{
RegexAutomata regexAutomata = NFAtoRegEx.ConvertNFAToRegEx(automata);
CreateAutomatePicture(NFAtoRegEx.CreateRegexAutomataDotString(regexAutomata));
return(regexAutomata.Nodes[0].Connections[0].Expression, regexAutomata.Nodes[0].Connections[0].PreExpr);
}
public void RerouteTransitions(RegexNode toNode, RegexAutomata automata)
{
(List <RegexConnection>, string, string)splitTransitions = SplitSelfLoopingTransition(toNode);
List <RegexConnection> toTransitionList = splitTransitions.Item1;
string betweenTransition = splitTransitions.Item2;
string betweenPreTransition = splitTransitions.Item3;
foreach (RegexNode node in automata.Nodes)
{
//can assume this is only once since we union all double transitions
RegexConnection pruneConnection = null;
List <RegexConnection> addList = new List <RegexConnection>();
if (node != toNode)
{
foreach (RegexConnection trans in node.Connections)
{
if (trans.ToNode == toNode)
{
pruneConnection = trans;
foreach (RegexConnection toTransition in toTransitionList)
{
string newExpression = CreateNewExpressionString(trans.Expression, betweenTransition, toTransition.Expression);
string newPreExpr = CreateNewPreExpressionString(trans.PreExpr, betweenPreTransition, toTransition.PreExpr);
addList.Add(new RegexConnection(newExpression, newPreExpr, toTransition.ToNode));
}
}
}
}
node.Connections.Remove(pruneConnection);
node.Connections.AddRange(addList);
}
automata.Nodes.Remove(toNode);
}
public string CreateRegexAutomataDotString(RegexAutomata automata)
{
string dotString = "";
dotString += "digraph myAutomaton { \nrankdir=LR; \n\"\" [shape=none] \n";
foreach (RegexNode node in automata.Nodes)
{
string shape = "circle";
if (node.Final)
{
shape = "doublecircle";
}
dotString += $"\"{node.Name}\" [shape={shape}] \n";
}
dotString += "\n";
dotString += $"\"\" -> \"{automata.Nodes[0].Name}\" \n";
foreach (RegexNode node in automata.Nodes)
{
foreach (RegexConnection conn in node.Connections)
{
string expres = conn.Expression.Replace("∪", "|");
dotString += $"\"{node.Name}\" -> \"{conn.ToNode.Name}\" [label=\"{expres}\"] \n";
}
}
dotString += "}";
return(dotString);
}
public RegexAutomata ConvertNFAToRegEx(Automata automata)
{
RegexAutomata regexAutomata = new RegexAutomata(automata);
UnionMultipleTransitions(regexAutomata);
regexAutomata = PruneNodes(regexAutomata);
return(regexAutomata);
}
public RegexAutomata PruneNodes(RegexAutomata automata)
{
int nodeCount = automata.Nodes.Count - 2;
if (nodeCount - 2 < 5)
{
RegexAutomata smalllestRegexGnfa = null;
IEnumerable <IEnumerable <int> > allPermutations = GetPermutations(Enumerable.Range(1, nodeCount), nodeCount);
foreach (IEnumerable <int> permutation in allPermutations)
{
RegexAutomata automataCopy = automata.DeepClone();
List <RegexNode> nodeOrder = new List <RegexNode>();
foreach (int nodeIndex in permutation)
{
nodeOrder.Add(automataCopy.Nodes[nodeIndex]);
}
foreach (RegexNode currentNode in nodeOrder)
{
RerouteTransitions(currentNode, automataCopy);
UnionMultipleTransitions(automataCopy);
}
Console.WriteLine($"Permutation {{{PermutationString(permutation)}}}: {automataCopy.Nodes[0].Connections[0].PreExpr}");
if (smalllestRegexGnfa == null || smalllestRegexGnfa.Nodes[0].Connections[0].PreExpr.Length > automataCopy.Nodes[0].Connections[0].PreExpr.Length)
{
smalllestRegexGnfa = automataCopy;
}
}
return(smalllestRegexGnfa);
}
else
{
while (automata.Nodes.Count > 2)
{
RegexNode currentNode = automata.Nodes[1];
RerouteTransitions(currentNode, automata);
UnionMultipleTransitions(automata);
}
return(automata);
}
}
public void UnionMultipleTransitions(RegexAutomata automata)
{
foreach (RegexNode node in automata.Nodes)
{
Dictionary <RegexNode, List <RegexConnection> > transitionsPerNode = new Dictionary <RegexNode, List <RegexConnection> >();
foreach (RegexConnection trans in node.Connections)
{
if (transitionsPerNode.ContainsKey(trans.ToNode))
{
transitionsPerNode[trans.ToNode].Add(trans);
}
else
{
transitionsPerNode.Add(trans.ToNode, new List <RegexConnection>()
{
trans
});
}
}
if (transitionsPerNode.Count != node.Connections.Count)
{
List <RegexConnection> newTransitions = new List <RegexConnection>();
foreach (KeyValuePair <RegexNode, List <RegexConnection> > valuePair in transitionsPerNode)
{
HashSet <string> uniqueExprs = new HashSet <string>();
HashSet <string> uniquePreExprs = new HashSet <string>();
foreach (RegexConnection connection in valuePair.Value)
{
uniqueExprs.Add(connection.Expression);
uniquePreExprs.Add(connection.PreExpr);
}
//infix expr
string newExpr = "";
foreach (string expr in uniqueExprs)
{
if (expr.Length == 1 || (expr.Substring(0, 1).Equals("(") && expr.Substring(expr.Length - 1, 1).Equals(")")))
{
newExpr += $"{expr}∪";
}
else
{
newExpr += $"({expr})∪";
}
}
string newPreExpr = "";
//prefix expr
bool firstPreExpr = false;
foreach (string preExpr in uniquePreExprs)
{
if (!firstPreExpr)
{
firstPreExpr = true;
newPreExpr = preExpr;
}
else
{
newPreExpr = $"|({newPreExpr},{preExpr})";
}
}
newTransitions.Add(new RegexConnection(newExpr.Substring(0, newExpr.Length - 1), newPreExpr, valuePair.Key));
}
node.Connections = newTransitions;
}
}
}
