public void AddRowState(RowState row)
{
if (!RowStates.Contains(row))
{
RowStates.Add(row);
}
}
public State CreateNextState(ISymbol symbol)
{
State newstate = new State(_preprocessor, _isClr);
foreach (RowState rowState in RowStates)
{
var symbolInPosition = rowState.GetSymbolInPosition();
if (symbolInPosition != null && symbolInPosition.Equals(symbol))
{
RowState newRowState = rowState.Clone();
newRowState.IncrementPosition();
newstate.AddRowState(newRowState);
}
}
return(newstate);
}
/// <summary>
/// the order is horrible. I did this to support Recursive LL(1) Grammers
/// Error :Collection was modified.
/// </summary>
public void AddClosures()
{
bool changed;
do
{
changed = false;
foreach (RowState state in RowStates.ToList())
{
if (state.GetSymbolInPosition() is Variable variable)
{
var defaultLookAhead = state.LookAhead;
// if there is no B,
if (_isClr && state.HasSymbolAfterPosition())
{
//first (B{PreviousLookAhead})
var symbolsAfterPosition = state.GetSymbolsAfterPosition().ToList();
//symbolsAfterPosition.AddRange(defaultLookAhead);
defaultLookAhead = _preprocessor.FirstSet(new List <IEnumerable <ISymbol> > {
symbolsAfterPosition
});
if (defaultLookAhead.Contains(Terminal.Epsilon))
{
defaultLookAhead.Remove(Terminal.Epsilon);
defaultLookAhead.AddRange(state.LookAhead);
}
}
variable.RuleSet.Definitions
.ForEach(rule =>
{
RowState rowState = new RowState(variable, rule);
if (_isClr)
{
rowState = new RowState(variable, rule, defaultLookAhead);
}
if (!RowStates.Contains(rowState))
{
RowStates.Add(rowState);
changed = true;
}
});
}
}
} while (changed);
}
public void InitializeAllStates()
{
Queue <State> queue = new Queue <State>();
State firstState = new State(_preprocessor, _isClr);
foreach (var rule in _grammarRules.HeadVariable.RuleSet.Definitions)
{
var rowState = new RowState(_grammarRules.HeadVariable, rule);
if (_isClr)
{
rowState.LookAhead = new List <Terminal>()
{
Terminal.EndOfFile
}
}
;
firstState.AddRowState(rowState);
}
firstState.AddClosures();
queue.Enqueue(firstState);
States.Add(firstState);
int stateNo = 1;
while (queue.Count > 0)
{
var state = queue.Dequeue();
//producing new items
var extractFirstSymbol = state.ExtractFirstSymbol().Distinct();
foreach (ISymbol symbol in extractFirstSymbol)
{
var nextState = state.CreateNextState(symbol);
nextState.AddClosures();
if (nextState.RowStates.Count > 0)
{
nextState.PreviousState = state;
nextState.TransferredSymbol = symbol;
//It's right not to add the state
if (!States.Contains(nextState))
{
queue.Enqueue(nextState);
nextState.StateId = stateNo;
stateNo++;
States.Add(nextState);
//if it's not the first State
if (!state.NextStates.ContainsKey(symbol))
{
state.NextStates.Add(symbol, nextState);
}
}
else
{//but we should add next state to know where to go
state.NextStates.Add(symbol, States.First(f => f.Equals(nextState)));
}
}
}
}
}
