private Node ConnectEntry(Node source, Entry entry)
{
return(entry switch
{
MatchEntry matchEntry => ConnectMatch(source, matchEntry),
StateEntry stateEntry => ConnectState(source, stateEntry, stateEntry.State.Inline || Automata.ForceInlineAll),
QuantifierEntry quantifierEntry => ConnectQuantifier(source, quantifierEntry),
PredicateEntryBase predicateEntry => ConnectPredicate(source, predicateEntry),
ActionEntry actionEntry => ConnectAction(source, actionEntry),
EpsilonEntry _ => source,
_ => throw new ArgumentOutOfRangeException(nameof(entry))
});
private static void EliminateLeftRecursion(ParserState parserState, List <ParserProduction> productions)
{
var hasLeftRecursion = false;
foreach (var stateProduction in productions)
{
stateProduction.LeftRecursionClassifier = Classify(stateProduction, parserState);
hasLeftRecursion |= IsLeftRecursion(stateProduction.LeftRecursionClassifier);
}
if (hasLeftRecursion == false)
{
return;
}
var count = productions.Count;
var recursionState = new ParserState(null, true);
var index = 0;
foreach (var production in productions)
{
if (production.LeftRecursionClassifier == LeftRecursionClassifier.Binary ||
production.LeftRecursionClassifier == LeftRecursionClassifier.Ternary ||
production.LeftRecursionClassifier == LeftRecursionClassifier.Prefix)
{
var assoc = production.IsRightAssoc ? 0 : 1;
var nextPriority = new PriorityStateEntryContext(count - index + assoc);
foreach (var parserStateEntry in production.Entries.Skip(1).OfType <ParserStateEntry>().Where(e => ReferenceEquals(e.State, parserState)))
{
parserStateEntry.StateEntryContext = nextPriority;
}
}
if (IsLeftRecursion(production.LeftRecursionClassifier) == false)
{
continue;
}
production.LeftRecursionEntry = (ParserStateEntry)production.Entries[0];
production.Entries[0] = ShouldPrefixPredicate(production.LeftRecursionClassifier) ? (Entry) new LeftRecursionPredicate(parserState, count - index).Entry : EpsilonEntry.Instance;
recursionState.Productions.Add(production);
index++;
}
var quantifierEntry = new QuantifierEntry(new StateEntry(recursionState)
{
SkipStack = true
}, QuantifierKind.ZeroOrMore, QuantifierMode.Greedy);
var primaryState = new ParserState(null, true);
primaryState.Productions.AddRange(productions.Where(production => IsLeftRecursion(production.LeftRecursionClassifier) == false));
productions.Clear();
productions.Add(new ParserProduction(new Entry[] { new StateEntry(primaryState)
{
SkipStack = true
}, quantifierEntry }));
}
