private void PropagateLookaheads()
{
LRItemList currentList = new LRItemList();
//first collect all items
foreach (ParserState state in Data.States)
{
currentList.AddRange(state.Items);
}
//Main loop - propagate until done
while (currentList.Count > 0)
{
LRItemList newList = new LRItemList();
foreach (LRItem item in currentList)
{
if (item.NewLookaheads.Count == 0)
{
continue;
}
int oldCount = item.Lookaheads.Count;
item.Lookaheads.AddRange(item.NewLookaheads);
if (item.Lookaheads.Count != oldCount)
{
foreach (LRItem targetItem in item.PropagateTargets)
{
targetItem.NewLookaheads.AddRange(item.NewLookaheads);
newList.Add(targetItem);
} //foreach targetItem
} //if
item.NewLookaheads.Clear();
} //foreach item
currentList = newList;
} //while
} //method
private void PropagateLookaheads()
{
LRItemList currentList = new LRItemList();
_data.States.ForEach(state => currentList.AddRange(state.Items));
while (currentList.Count > 0)
{
LRItemList newList = new LRItemList();
foreach (LRItem item in currentList)
{
if (item.NewLookaheads.Count == 0)
{
continue;
}
int oldCount = item.Lookaheads.Count;
item.Lookaheads.AddRange(item.NewLookaheads);
if (item.Lookaheads.Count != oldCount)
{
foreach (LRItem targetItem in item.PropagateTargets)
{
targetItem.NewLookaheads.AddRange(item.NewLookaheads);
newList.Add(targetItem);
}
}
item.NewLookaheads.Clear();
}
currentList = newList;
}
}
} //method
private void ResolveConflictByHints(ParserState state, Terminal conflict)
{
var stateData = state.BuilderData;
//reduce hints
var reduceItems = stateData.ReduceItems.SelectByLookahead(conflict);
foreach (var reduceItem in reduceItems)
{
if (reduceItem.Core.Hints.Find(h => h.HintType == HintType.ResolveToReduce) != null)
{
state.Actions[conflict] = new ParserAction(ParserActionType.Reduce, null, reduceItem.Core.Production);
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
//Shift hints
var shiftItems = stateData.ShiftItems.SelectByCurrent(conflict);
foreach (var shiftItem in shiftItems)
{
if (shiftItem.Core.Hints.Find(h => h.HintType == HintType.ResolveToShift) != null)
{
//shift action is already there
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
//code hints
// first prepare data for conflict action: reduceProduction (for possible reduce) and newState (for possible shift)
var reduceProduction = reduceItems.First().Core.Production; //take first of reduce productions
ParserState newState = (state.Actions.ContainsKey(conflict) ? state.Actions[conflict].NewState : null);
// Get all items that might contain hints;
var allItems = new LRItemList();
allItems.AddRange(state.BuilderData.ShiftItems.SelectByCurrent(conflict));
allItems.AddRange(state.BuilderData.ReduceItems.SelectByLookahead(conflict));
// Scan all items and try to find hint with resolution type Code
foreach (var item in allItems)
{
if (item.Core.Hints.Find(h => h.HintType == HintType.ResolveInCode) != null)
{
state.Actions[conflict] = new ParserAction(ParserActionType.Code, newState, reduceProduction);
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
}
private bool TryResolveConflictByHints(ParserState state, BnfTerm conflict)
{
var stateData = state.BuilderData;
//reduce hints
var reduceItems = stateData.ReduceItems.SelectByLookahead(conflict);
foreach(var reduceItem in reduceItems)
if (reduceItem.Core.Hints != null)
foreach (var hint in reduceItem.Core.Hints)
if (hint.HintType == HintType.ResolveToReduce) {
var newAction = ParserAction.CreateReduce(reduceItem.Core.Production);
state.Actions[conflict] = newAction; //replace/add reduce action
return true;
}
//Shift hints
var shiftItems = stateData.ShiftItems.SelectByCurrent(conflict);
foreach (var shiftItem in shiftItems)
if (shiftItem.Core.Hints != null)
foreach (var hint in shiftItem.Core.Hints)
if (hint.HintType == HintType.ResolveToShift) {
//shift action is already there
return true;
}
//code hints
// first prepare data for conflict action: reduceProduction (for possible reduce) and newState (for possible shift)
var reduceProduction = reduceItems.First().Core.Production; //take first of reduce productions
ParserState newState = (state.Actions.ContainsKey(conflict) ? state.Actions[conflict].NewState : null);
// Get all items that might contain hints; first take all shift items and reduce items in conflict;
// we should also add lookahead sources of reduce items. Lookahead source is an LR item that produces the lookahead,
// so if it contains a code hint right before the lookahead term, then it applies to this conflict as well.
var allItems = new LRItemList();
allItems.AddRange(shiftItems);
foreach (var reduceItem in reduceItems) {
allItems.Add(reduceItem);
allItems.AddRange(reduceItem.ReducedLookaheadSources);
}
// Scan all items and try to find hint with resolution type Code
foreach (var item in allItems)
if (item.Core.Hints != null)
foreach (var hint in item.Core.Hints)
if (hint.HintType == HintType.ResolveInCode) {
//found hint with resolution type "code" - this is instruction to use custom code here to resolve the conflict
// create new ConflictAction and place it into Actions table
var newAction = ParserAction.CreateCodeAction(newState, reduceProduction);
state.Actions[conflict] = newAction; //replace/add reduce action
return true;
}
return false;
}
private void ResolveConflictByHints(ParserState state, Terminal conflict)
{
var stateData = state.BuilderData;
//reduce hints
var reduceItems = stateData.ReduceItems.SelectByLookahead(conflict);
foreach(var reduceItem in reduceItems)
if(reduceItem.Core.Hints.Find(h => h.HintType == HintType.ResolveToReduce) != null) {
state.Actions[conflict] = new ParserAction(ParserActionType.Reduce, null, reduceItem.Core.Production);
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
//Shift hints
var shiftItems = stateData.ShiftItems.SelectByCurrent(conflict);
foreach (var shiftItem in shiftItems)
if(shiftItem.Core.Hints.Find(h => h.HintType == HintType.ResolveToShift) != null) {
//shift action is already there
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
//code hints
// first prepare data for conflict action: reduceProduction (for possible reduce) and newState (for possible shift)
var reduceProduction = reduceItems.First().Core.Production; //take first of reduce productions
ParserState newState = (state.Actions.ContainsKey(conflict) ? state.Actions[conflict].NewState : null);
// Get all items that might contain hints;
var allItems = new LRItemList();
allItems.AddRange(state.BuilderData.ShiftItems.SelectByCurrent(conflict));
allItems.AddRange(state.BuilderData.ReduceItems.SelectByLookahead(conflict));
// Scan all items and try to find hint with resolution type Code
foreach (var item in allItems)
if(item.Core.Hints.Find(h => h.HintType == HintType.ResolveInCode) != null) {
state.Actions[conflict] = new ParserAction(ParserActionType.Code, newState, reduceProduction);
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
private bool TryResolveConflictByHints(ParserState state, BnfTerm conflict)
{
var stateData = state.BuilderData;
//reduce hints
var reduceItems = stateData.ReduceItems.SelectByLookahead(conflict);
foreach (var reduceItem in reduceItems)
{
if (reduceItem.Core.Hints != null)
{
foreach (var hint in reduceItem.Core.Hints)
{
if (hint.HintType == HintType.ResolveToReduce)
{
var newAction = ParserAction.CreateReduce(reduceItem.Core.Production);
state.Actions[conflict] = newAction; //replace/add reduce action
return(true);
}
}
}
}
//Shift hints
var shiftItems = stateData.ShiftItems.SelectByCurrent(conflict);
foreach (var shiftItem in shiftItems)
{
if (shiftItem.Core.Hints != null)
{
foreach (var hint in shiftItem.Core.Hints)
{
if (hint.HintType == HintType.ResolveToShift)
{
//shift action is already there
return(true);
}
}
}
}
//code hints
// first prepare data for conflict action: reduceProduction (for possible reduce) and newState (for possible shift)
var reduceProduction = reduceItems.First().Core.Production; //take first of reduce productions
ParserState newState = (state.Actions.ContainsKey(conflict) ? state.Actions[conflict].NewState : null);
// Get all items that might contain hints; first take all shift items and reduce items in conflict;
// we should also add lookahead sources of reduce items. Lookahead source is an LR item that produces the lookahead,
// so if it contains a code hint right before the lookahead term, then it applies to this conflict as well.
var allItems = new LRItemList();
allItems.AddRange(shiftItems);
foreach (var reduceItem in reduceItems)
{
allItems.Add(reduceItem);
allItems.AddRange(reduceItem.ReducedLookaheadSources);
}
// Scan all items and try to find hint with resolution type Code
foreach (var item in allItems)
{
if (item.Core.Hints != null)
{
foreach (var hint in item.Core.Hints)
{
if (hint.HintType == HintType.ResolveInCode)
{
//found hint with resolution type "code" - this is instruction to use custom code here to resolve the conflict
// create new ConflictAction and place it into Actions table
var newAction = ParserAction.CreateCodeAction(newState, reduceProduction);
state.Actions[conflict] = newAction; //replace/add reduce action
return(true);
}
}
}
}
return(false);
}
private void PropagateLookaheads()
{
LRItemList currentList = new LRItemList();
_data.States.ForEach(state => currentList.AddRange(state.Items));
while (currentList.Count > 0)
{
LRItemList newList = new LRItemList();
foreach (LRItem item in currentList)
{
if (item.NewLookaheads.Count == 0) continue;
int oldCount = item.Lookaheads.Count;
item.Lookaheads.AddRange(item.NewLookaheads);
if (item.Lookaheads.Count != oldCount)
{
foreach (LRItem targetItem in item.PropagateTargets)
{
targetItem.NewLookaheads.AddRange(item.NewLookaheads);
newList.Add(targetItem);
}
}
item.NewLookaheads.Clear();
}
currentList = newList;
}
}
}//method
private void ResolveConflictByHints(ParserState state, Terminal conflict) {
var stateData = state.BuilderData;
//reduce hints
var reduceItems = stateData.ReduceItems.SelectByLookahead(conflict);
foreach(var reduceItem in reduceItems)
if(reduceItem.Core.Hints.Find(h => h.HintType == HintType.ResolveToReduce) != null) {
state.Actions[conflict] = new ParserAction(ParserActionType.Reduce, null, reduceItem.Core.Production);
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
//shift hints
var shiftItems = stateData.ShiftItems.SelectByCurrent(conflict);
foreach (var shiftItem in shiftItems)
if(shiftItem.Core.Hints.Find(h => h.HintType == HintType.ResolveToShift) != null) {
//shift action is already there
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
//code hints
// first prepare data for conflict action: reduceProduction (for possible reduce) and newState (for possible shift)
var reduceProduction = reduceItems.First().Core.Production; //take first of reduce productions
ParserState newState = (state.Actions.ContainsKey(conflict) ? state.Actions[conflict].NewState : null);
// Get all items that might contain hints;
var allItems = new LRItemList();
allItems.AddRange(state.BuilderData.ShiftItems.SelectByCurrent(conflict));
allItems.AddRange(state.BuilderData.ReduceItems.SelectByLookahead(conflict));
// Scan all items and try to find hint with resolution type Code
foreach (var item in allItems) {
if (item.Core.Hints.Find(h => h.HintType == HintType.ResolveInCode) != null) {
state.Actions[conflict] = new ParserAction(ParserActionType.Code, newState, reduceProduction);
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
//custom hints
// find custom grammar hints and build custom conflict resolver
var customHints = new List<CustomGrammarHint>();
var hintItems = new Dictionary<CustomGrammarHint, LRItem>();
LRItem defaultItem = null; // the first item with no hints
foreach (var item in allItems) {
var hints = item.Core.Hints.OfType<CustomGrammarHint>();
foreach (var hint in hints) {
customHints.Add(hint);
hintItems[hint] = item;
}
if (defaultItem == null && !hints.Any())
defaultItem = item;
}
// if there are custom hints, build conflict resolver
if (customHints.Count > 0) {
state.Actions[conflict] = new ParserAction(newState, reduceProduction, args => {
// examine all custom hints and select the first production that matched
foreach (var customHint in customHints) {
if (customHint.Match(args)) {
var item = hintItems[customHint];
// If the ReduceProduction was clear, then use the default production following the hints
if (args.ReduceProduction == null)
args.ReduceProduction = item.Core.Production;
return;
}
}
// no hints matched, select default LRItem
if (defaultItem != null) {
args.ReduceProduction = defaultItem.Core.Production;
args.Result = args.NewShiftState != null ? ParserActionType.Shift : ParserActionType.Reduce;
return;
}
// prefer Reduce if Shift operation is not available
args.Result = args.NewShiftState != null ? ParserActionType.Shift : ParserActionType.Reduce;
// TODO: figure out what to do next
});
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
} //method
private void ResolveConflictByHints(ParserState state, Terminal conflict)
{
var stateData = state.BuilderData;
//reduce hints
var reduceItems = stateData.ReduceItems.SelectByLookahead(conflict);
foreach (var reduceItem in reduceItems)
{
if (reduceItem.Core.Hints.Find(h => h.HintType == HintType.ResolveToReduce) != null)
{
state.Actions[conflict] = new ParserAction(ParserActionType.Reduce, null, reduceItem.Core.Production);
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
//shift hints
var shiftItems = stateData.ShiftItems.SelectByCurrent(conflict);
foreach (var shiftItem in shiftItems)
{
if (shiftItem.Core.Hints.Find(h => h.HintType == HintType.ResolveToShift) != null)
{
//shift action is already there
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
//code hints
// first prepare data for conflict action: reduceProduction (for possible reduce) and newState (for possible shift)
var reduceProduction = reduceItems.First().Core.Production; //take first of reduce productions
ParserState newState = (state.Actions.ContainsKey(conflict) ? state.Actions[conflict].NewState : null);
// Get all items that might contain hints;
var allItems = new LRItemList();
allItems.AddRange(state.BuilderData.ShiftItems.SelectByCurrent(conflict));
allItems.AddRange(state.BuilderData.ReduceItems.SelectByLookahead(conflict));
// Scan all items and try to find hint with resolution type Code
foreach (var item in allItems)
{
if (item.Core.Hints.Find(h => h.HintType == HintType.ResolveInCode) != null)
{
state.Actions[conflict] = new ParserAction(ParserActionType.Code, newState, reduceProduction);
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
//custom hints
// find custom grammar hints and build custom conflict resolver
var customHints = new List <CustomGrammarHint>();
var hintItems = new Dictionary <CustomGrammarHint, LRItem>();
LRItem defaultItem = null; // the first item with no hints
foreach (var item in allItems)
{
var hints = item.Core.Hints.OfType <CustomGrammarHint>();
foreach (var hint in hints)
{
customHints.Add(hint);
hintItems[hint] = item;
}
if (defaultItem == null && !hints.Any())
{
defaultItem = item;
}
}
// if there are custom hints, build conflict resolver
if (customHints.Count > 0)
{
state.Actions[conflict] = new ParserAction(newState, reduceProduction, args => {
// examine all custom hints and select the first production that matched
foreach (var customHint in customHints)
{
if (customHint.Match(args))
{
var item = hintItems[customHint];
args.ReduceProduction = item.Core.Production;
args.Result = customHint.Action;
return;
}
}
// no hints matched, select default LRItem
if (defaultItem != null)
{
args.ReduceProduction = defaultItem.Core.Production;
args.Result = args.NewShiftState != null ? ParserActionType.Shift : ParserActionType.Reduce;
return;
}
// prefer Reduce if Shift operation is not available
args.Result = args.NewShiftState != null ? ParserActionType.Shift : ParserActionType.Reduce;
// TODO: figure out what to do next
});
state.BuilderData.ResolvedConflicts.Add(conflict);
return;
}
}
