private void ComputeLookaheads(LRItemSet forItems)
{
foreach (var reduceItem in forItems)
{
// Find all source states - those that contribute lookaheads
var sourceStates = new ParserStateSet();
foreach (var lookbackTrans in reduceItem.Lookbacks)
{
sourceStates.Add(lookbackTrans.ToState);
sourceStates.UnionWith(lookbackTrans.ToState.BuilderData.ReadStateSet);
foreach (var includeTrans in lookbackTrans.Includes)
{
sourceStates.Add(includeTrans.ToState);
sourceStates.UnionWith(includeTrans.ToState.BuilderData.ReadStateSet);
} //foreach includeTrans
} //foreach lookbackTrans
//Now merge all shift terminals from all source states
foreach (var state in sourceStates)
{
reduceItem.Lookaheads.UnionWith(state.BuilderData.ShiftTerminals);
}
//Remove SyntaxError - it is pseudo terminal
if (reduceItem.Lookaheads.Contains(_grammar.SyntaxError))
{
reduceItem.Lookaheads.Remove(_grammar.SyntaxError);
}
//Sanity check
if (reduceItem.Lookaheads.Count == 0)
{
_language.Errors.Add(GrammarErrorLevel.InternalError, reduceItem.State, "Reduce item '{0}' in state {1} has no lookaheads.", reduceItem.Core, reduceItem.State);
}
} //foreach reduceItem
} //method
private void ComputeLookaheads(LRItemSet forItems)
{
foreach(var reduceItem in forItems) {
// Find all source states - those that contribute lookaheads
var sourceStates = new ParserStateSet();
foreach(var lookbackTrans in reduceItem.Lookbacks) {
sourceStates.Add(lookbackTrans.ToState);
sourceStates.UnionWith(lookbackTrans.ToState.BuilderData.ReadStateSet);
foreach(var includeTrans in lookbackTrans.Includes) {
sourceStates.Add(includeTrans.ToState);
sourceStates.UnionWith(includeTrans.ToState.BuilderData.ReadStateSet);
}//foreach includeTrans
}//foreach lookbackTrans
//Now merge all shift terminals from all source states
foreach(var state in sourceStates)
reduceItem.Lookaheads.UnionWith(state.BuilderData.ShiftTerminals);
//Remove SyntaxError - it is pseudo terminal
if (reduceItem.Lookaheads.Contains(_grammar.SyntaxError))
reduceItem.Lookaheads.Remove(_grammar.SyntaxError);
//Sanity check
if (reduceItem.Lookaheads.Count == 0)
_language.Errors.Add(GrammarErrorLevel.InternalError, reduceItem.State, "Reduce item '{0}' in state {1} has no lookaheads.", reduceItem.Core, reduceItem.State);
}//foreach reduceItem
}
