public static Node Parse(GrammarDefinition grammar, string source)
{
FullLalrState lalrState = new FullLalrState();
lalrState.StateStack.Add(grammar.Table[0]); //push state 0
foreach (var tk in Lexer.Lex(grammar, source))
{
var currentSymbol = new TerminalSymbol(tk.Name);
DontConsumeToken:
{
var currentState = lalrState.StateStack[lalrState.StateStack.Count - 1];
if (!currentState.ContainsKey(currentSymbol))
{
throw new GrammarException(tk.Location, $"token inesperado {tk.Source}");
}
var action = currentState[currentSymbol].First();
if (action is LalrShift)
{
var s = action as LalrShift;
lalrState.NodeStack.Add(Node.FromToken(tk));
lalrState.StateStack.Add(s.State);
}
else if (action is LalrReduce)
{
var prod = ((LalrReduce)action).Production;
Reduce(grammar, prod, lalrState);
currentState = lalrState.StateStack[lalrState.StateStack.Count - 1];
lalrState.StateStack.Add(((LalrGoto)currentState[prod.Head].First()).State);
goto DontConsumeToken;
}
else
{
//accept
SetParent(lalrState.NodeStack.First(), null);
return(lalrState.NodeStack.First());
}
}
}
//should never get here
throw new InvalidOperationException();
}
private static void Reduce(GrammarDefinition definition, GrammarProduction production, FullLalrState lalrState)
{
List <Node> toBeReduced = new List <Node>();
for (int i = 0; i < production.Body.Count; i++)
{
toBeReduced.Add(lalrState.NodeStack[lalrState.NodeStack.Count - 1]);
lalrState.NodeStack.RemoveAt(lalrState.NodeStack.Count - 1);
lalrState.StateStack.RemoveAt(lalrState.StateStack.Count - 1);
}
toBeReduced.Reverse();
lalrState.NodeStack.Add(Node.FromNodes(definition.ProductionNames[production], production, toBeReduced));
}
