static ParseItemSet Closure(SegmentSetProvider provider, ParseItemSet kernelItems)
{
var lookup = new Dictionary <ParseItem, bool>();
var itemsToAdd = new Queue <ParseItem>();
EnqueueRange(itemsToAdd, kernelItems);
while (itemsToAdd.Count > 0)
{
var item = itemsToAdd.Dequeue();
var production = item.Production;
if (!lookup.ContainsKey(item))
{
lookup.Add(item, true);
if (item.Position < production.Segments.Length)
{
var next = production.Segments[item.Position];
if (!next.IsTerminal)
{
EnqueueRange(itemsToAdd, provider.CreateParseItems(next));
}
}
}
}
return(ParseItemSet.New(lookup.Keys));
}
static ParseGraph ConstructGraph(Config config, SegmentSetProvider provider)
{
var graphBuilder = new Graph.Builder();
var map = new Dictionary <ParseItemSet, Graph.State>();
var queue = new Queue <Graph.State>();
var startStates = new List <Graph.State>();
var topLevelSegments = new List <Segment>();
foreach (var segment in provider.InitialSegments)
{
var initialKernel = ParseItemSet.New(provider.CreateParseItems(segment));
var initialState = graphBuilder.NewState(true, Closure(provider, initialKernel));
map.Add(initialKernel, initialState);
queue.Enqueue(initialState);
startStates.Add(initialState);
topLevelSegments.Add(new Segment(segment.Name, false));
}
while (queue.Count > 0)
{
var fromState = queue.Dequeue();
foreach (var pair in fromState.Label.GetTransitionKernels())
{
if (!map.TryGetValue(pair.Value, out var toState))
{
toState = graphBuilder.NewState(false, Closure(provider, pair.Value));
map.Add(pair.Value, toState);
queue.Enqueue(toState);
}
graphBuilder.AddTransition(fromState, toState, pair.Key);
}
}
var graph = graphBuilder.Graph;
PopulateLookaheads(provider, graph);
ParseGraphOptimiser.Optimise(config, graphBuilder);
return(new ParseGraph(graph, topLevelSegments.ToArray(), startStates.ToArray()));
}