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;
}
}
public ParserState(string name, LR0ItemList coreItems)
{
Name = name;
foreach (LR0Item coreItem in coreItems)
{
Items.Add(new LRItem(this, coreItem));
}
}
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 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;
}
}
public ParserState(string name, LRItem item)
{
Name = name;
Items.Add(item);
}
