private Dictionary <ParserConstructionItemSet, ItemSetGraphInformation> ConstructStateTransitionGraph()
{
ParserConstructionItemSet intialStateSet = GetInitialState();
Dictionary <ParserConstructionItemSet, ItemSetGraphInformation> shiftGraph = new Dictionary <ParserConstructionItemSet, ItemSetGraphInformation>();
shiftGraph.Add(intialStateSet, new ItemSetGraphInformation {
Id = 0
});
HashSet <ParserConstructionItemSet> processedStates = new HashSet <ParserConstructionItemSet>();
Queue <ParserConstructionItemSet> setsToProcess = new Queue <ParserConstructionItemSet>();
setsToProcess.Enqueue(intialStateSet);
while (setsToProcess.Count > 0)
{
var curSet = setsToProcess.Dequeue();
if (processedStates.Contains(curSet))
{
continue;
}
var curStateInfo = shiftGraph[curSet];
var targetStates = GetShiftedStates(curSet, intialStateSet);
foreach (var targetState in targetStates)
{
if (shiftGraph.TryGetValue(targetState.Value, out var existingTargetStateInfo))
{
curStateInfo.ShiftToIds.Add(targetState.Key, existingTargetStateInfo.Id);
}
else
{
int newStateId = shiftGraph.Count;
shiftGraph.Add(targetState.Value, new ItemSetGraphInformation {
Id = newStateId
});
curStateInfo.ShiftToIds.Add(targetState.Key, newStateId);
setsToProcess.Enqueue(targetState.Value);
}
}
processedStates.Add(curSet);
}
return(shiftGraph);
}
private ParserConstructionItemSet GetShiftedState(IEnumerable <GrammarRuleOffset> offsets, ParserConstructionItemSet initialSet)
{
var shiftedSeedOffsets = offsets.Select(o => o.Shift()).Where(i => i.IsValid);
var result = CalculateItemSetEnclosure(shiftedSeedOffsets);
if (_grammar.IsSkipGrammar)
{
result.UnionWith(initialSet.RuleOffsets);
}
return(new ParserConstructionItemSet
{
RuleOffsets = result
});
}
private Dictionary <GrammarRuleToken, ParserConstructionItemSet> GetShiftedStates(ParserConstructionItemSet currentSet, ParserConstructionItemSet initialSet)
{
var result = currentSet
.RuleOffsets
.Where(o => !o.IsFinal)
.GroupBy(o => o.NextToken)
.ToDictionary(g => g.Key, g => GetShiftedState(g, initialSet));
if (_grammar.IsSkipGrammar)
{
result.Add(_grammar.SkipToken, initialSet);
}
return(result);
}
