private void Completer(
State state,
Item item,
IDictionary<Production,IList<Item>> completedNullable)
{
Debug.Assert(item.AtEnd);
if (item.Parent == state)
{
// completed a nullable item
if (!completedNullable.ContainsKey(item.Production))
{
completedNullable[item.Production] = new List<Item>();
}
completedNullable[item.Production].Add(item);
}
foreach (Item parentItem in item.Parent.GetItems(item.Production))
{
Item newItem = state.Import(parentItem.NextItem);
newItem.Add(item);
ShiftCompletedNullable(state, newItem, completedNullable);
}
}
public void ImportIncompatible()
{
Production p = new Production(new Terminal('a', 'b'));
Item item = new Item(p, new State());
State s = new State();
Item next = item.NextItem;
next.Add('a');
s.Add(next);
Item newNext = item.NextItem;
newNext.Add('b');
s.Import(newNext);
}
public void Import()
{
Production p = new Production(new Terminal('a', 'b'));
Item item = new Item(p, new State());
State s = new State();
Item next = item.NextItem;
next.Add('a');
s.Add(next);
Item imported = s.Import(item.NextItem);
Assert.AreSame(next, imported);
item = new Item(new Production(), new State());
imported = s.Import(item);
Assert.AreSame(item, imported);
}
// When an item is added to the current state, any nullable
// productions that have already been completed need to be
// added to the new item
private void ShiftCompletedNullable(
State state,
Item item,
IDictionary<Production, IList<Item>> completedNullable)
{
if (!item.AtEnd && item.Symbol is Nonterminal)
{
Item nextItem = null;
foreach (Production p in completedNullable.Keys)
{
if (((Nonterminal)item.Symbol).Contains(p))
{
if (nextItem == null)
{
nextItem = state.Import(item.NextItem);
}
foreach (Item nullableItem in completedNullable[p])
{
nextItem.Add(nullableItem);
}
}
}
if (nextItem != null)
{
ShiftCompletedNullable(state, nextItem, completedNullable);
}
}
}