public bool Equals(EarleyItem item)
{
if(ReferenceEquals(item, this)) return true;
return
_production == item._production
&& _position == item._position
&& _parent == item._parent;
}
private IEnumerable<EarleyItem> Complete(EarleyItem item)
{
if(item.IsComplete)
{
foreach(var parentItem in item.Parent)
{
if (item.Production.LeftSide.Equals(parentItem.NextProductionSymbol))
{
yield return new EarleyItem(parentItem.Production, parentItem.Position + 1, parentItem.Parent);
}
}
}
}
private IEnumerable<EarleyItem> Scan(EarleyItem item, char c)
{
var nextSymbol = item.NextProductionSymbol as Terminal;
if (nextSymbol != null)
{
if (nextSymbol.Matches(c))
{
yield return new EarleyItem(item.Production, item.Position + 1, item.Parent);
}
}
}
private IEnumerable<EarleyItem> Predict(EarleyItem item, List<EarleyItem> parent)
{
var nextSymbol = item.NextProductionSymbol as Nonterminal;
if(nextSymbol != null)
{
foreach(var production in nextSymbol.Productions)
{
yield return new EarleyItem(production, 0, parent);
}
if(nextSymbol.IsNullable) yield return new EarleyItem(item.Production, item.Position + 1, item.Parent);
}
}