public ParseState this[ParseState current, BnfTerm symbol]
{
get
{
Dictionary<BnfTerm, ParseState> transition;
if (!transitionRules.TryGetValue(current, out transition))
{
if (!allStates.Contains(current))
throw new ParseException("No such state");
else
return null;
}
ParseState next;
if (!transition.TryGetValue(symbol, out next))
{
HashSet<Terminal> expected = new HashSet<Terminal>();
foreach (var item in current)
{
if (item.Position < item.Production.Body.Length)
expected.UnionWith(grammar.GetFirstSet(item.Production.Body[item.Position]));
}
throw new ParseException("Invalid symbol " + symbol.ToString() + " expected one of [" + String.Join(", ", expected.Select(a => a.Name)) + "]");
}
return next;
}
}
public static ParseState Goto(this IEnumerable<Item> state, BnfTerm symbol, Grammar grammar)
{
HashSet<Item> items = new HashSet<Item>();
foreach (var item in state)
{
if (item.Production.Body.Length == item.Position)
continue;
BnfTerm term = item.Production.Body[item.Position];
if (term.Equals(symbol))
items.Add(new Item(item.Production, item.Position + 1));
}
return items.Closure(grammar);
}
public static ParseState Goto(this IEnumerable <Item> state, BnfTerm symbol, Grammar grammar)
{
HashSet <Item> items = new HashSet <Item>();
foreach (var item in state)
{
if (item.Production.Body.Length == item.Position)
{
continue;
}
BnfTerm term = item.Production.Body[item.Position];
if (term.Equals(symbol))
{
items.Add(new Item(item.Production, item.Position + 1));
}
}
return(items.Closure(grammar));
}
public static ConcatenationRule Plus(BnfTerm left, BnfTerm right)
{
return(new ConcatenationRule(left, right));
}
public ParseStateTransition(ParseState start, BnfTerm trigger, ParseState end)
{
Start = start;
Trigger = trigger;
End = end;
}
public static ConcatenationRule Plus(BnfTerm left, BnfTerm right)
{
return new ConcatenationRule(left, right);
}
