private IForestNode CreateNullParseNode(ISymbol symbol, int location)
{
var symbolNode = _nodeSet.AddOrGetExistingSymbolNode(symbol, location, location);
var token = new Token(string.Empty, location, EmptyTokenType);
var nullNode = new TokenForestNode(token, location, location);
symbolNode.AddUniqueFamily(nullNode);
return(symbolNode);
}
public void ParseEngineGivenAmbiguousNullableRightRecursionShouldCreateMultipleParsePaths()
{
// example 1 section 3, Elizabeth Scott
var tokens = Tokenize("aa");
ProductionExpression
S = "S",
T = "T",
B = "B";
S.Rule = (S + T) | "a";
B.Rule = null;
T.Rule = ("a" + B) | "a";
var grammar = new GrammarExpression(S, new[] { S, T, B }).ToGrammar();
var parseEngine = new ParseEngine(grammar, new ParseEngineOptions(false));
ParseInput(parseEngine, tokens);
var parseForestRoot = parseEngine.GetParseForestRootNode();
var actual = parseForestRoot;
var a_1_2 = new TokenForestNode(MakeToken("a", 1));
var expected =
new SymbolForestNode(
S.ProductionModel.LeftHandSide.NonTerminal,
0,
2,
new AndForestNode(
new SymbolForestNode(
S.ProductionModel.LeftHandSide.NonTerminal,
0,
1,
new AndForestNode(new TokenForestNode(MakeToken("a", 0)))),
new SymbolForestNode(
T.ProductionModel.LeftHandSide.NonTerminal,
1,
2,
new AndForestNode(a_1_2),
new AndForestNode(
a_1_2,
new SymbolForestNode(
B.ProductionModel.LeftHandSide.NonTerminal,
2,
2,
new AndForestNode(new SymbolForestNode(B.ProductionModel.LeftHandSide.NonTerminal, 2, 2)))))));
AssertForestsAreEqual(expected, actual);
}
