/// <summary>
/// Parses the input and returns the produced AST
/// </summary>
/// <returns>AST produced by the parser representing the input, or null if unrecoverable errors were encountered</returns>
public override ParseResult Parse()
{
reductions = new Queue <Reduction>();
shifts = new Queue <Shift>();
int Ui = gss.CreateGeneration();
int v0 = gss.CreateNode(0);
nextToken = lexer.GetNextToken(this);
// bootstrap the shifts and reductions queues
int count = parserAutomaton.GetActionsCount(0, nextToken.TerminalID);
for (int i = 0; i != count; i++)
{
LRAction action = parserAutomaton.GetAction(0, nextToken.TerminalID, i);
if (action.Code == LRActionCode.Shift)
{
shifts.Enqueue(new Shift(v0, action.Data));
}
else if (action.Code == LRActionCode.Reduce)
{
reductions.Enqueue(new Reduction(v0, parserAutomaton.GetProduction(action.Data), SPPF.EPSILON));
}
}
while (nextToken.TerminalID != Symbol.SID_EPSILON) // Wait for ε token
{
// the stem length (initial number of nodes in the generation before reductions)
int stem = gss.GetGeneration(Ui).Count;
// apply all reduction actions
Reducer(Ui);
// no scheduled shift actions?
if (shifts.Count == 0)
{
// the next token was not expected
OnUnexpectedToken(stem);
return(new ParseResult(new ROList <ParseError>(allErrors), lexer.Input));
}
// look for the next next-token
Lexer.TokenKernel oldtoken = nextToken;
nextToken = lexer.GetNextToken(this);
// apply the scheduled shift actions
Ui = Shifter(oldtoken);
}
GSSGeneration genData = gss.GetGeneration(Ui);
for (int i = genData.Start; i != genData.Start + genData.Count; i++)
{
int state = gss.GetRepresentedState(i);
if (parserAutomaton.IsAcceptingState(state))
{
// Has reduction _Axiom_ -> axiom $ . on ε
GSSPath[] paths = gss.GetPaths(i, 2, out count);
return(new ParseResult(new ROList <ParseError>(allErrors), lexer.Input, sppf.GetTree(paths[0][1])));
}
}
// At end of input but was still waiting for tokens
return(new ParseResult(new ROList <ParseError>(allErrors), lexer.Input));
}
/// <summary>
/// Initializes a new automaton from the given binary stream
/// </summary>
/// <param name="reader">The binary stream to load from</param>
public LRkAutomaton(BinaryReader reader)
{
ncols = reader.ReadUInt16();
nstates = reader.ReadUInt16();
int nprod = reader.ReadUInt16();
columns = new ColumnMap();
for (int i = 0; i != ncols; i++)
{
columns.Add(reader.ReadUInt16(), i);
}
contexts = new LRContexts[nstates];
for (int i = 0; i != nstates; i++)
{
contexts[i] = new LRContexts(reader);
}
table = new LRAction[nstates * ncols];
for (int i = 0; i != nstates * ncols; i++)
{
table[i] = new LRAction(reader);
}
productions = new LRProduction[nprod];
for (int i = 0; i != nprod; i++)
{
productions[i] = new LRProduction(reader);
}
}
/// <summary>
/// Executes a shift operation
/// </summary>
/// <param name="gen">The GSS generation to start from</param>
/// <param name="label">The GSS label to use for the new GSS edges</param>
/// <param name="shift">The shift operation</param>
private void ExecuteShift(int gen, int label, Shift shift)
{
int w = gss.FindNode(gen, shift.to);
if (w != -1)
{
// A node for the target state is already in the GSS
gss.CreateEdge(w, shift.from, label);
// Look for the new reductions at this state
int count = parserAutomaton.GetActionsCount(shift.to, nextToken.TerminalID);
for (int i = 0; i != count; i++)
{
LRAction action = parserAutomaton.GetAction(shift.to, nextToken.TerminalID, i);
if (action.Code == LRActionCode.Reduce)
{
LRProduction prod = parserAutomaton.GetProduction(action.Data);
// length 0 reduction are not considered here because they already exist at this point
if (prod.ReductionLength != 0)
{
reductions.Enqueue(new Reduction(shift.from, prod, label));
}
}
}
}
else
{
// Create the new corresponding node in the GSS
w = gss.CreateNode(shift.to);
gss.CreateEdge(w, shift.from, label);
// Look for all the reductions and shifts at this state
int count = parserAutomaton.GetActionsCount(shift.to, nextToken.TerminalID);
for (int i = 0; i != count; i++)
{
LRAction action = parserAutomaton.GetAction(shift.to, nextToken.TerminalID, i);
if (action.Code == LRActionCode.Shift)
{
shifts.Enqueue(new Shift(w, action.Data));
}
else if (action.Code == LRActionCode.Reduce)
{
LRProduction prod = parserAutomaton.GetProduction(action.Data);
if (prod.ReductionLength == 0) // Length 0 => reduce from the head
{
reductions.Enqueue(new Reduction(w, prod, SPPF.EPSILON));
}
else // reduce from the second node on the path
{
reductions.Enqueue(new Reduction(shift.from, prod, label));
}
}
}
}
}
/// <summary>
/// Gets the next RNGLR state by a shift with the given variable ID
/// </summary>
/// <param name="state">A RNGLR state</param>
/// <param name="var">A variable ID</param>
/// <returns>The next RNGLR state, or 0xFFFF if no transition is found</returns>
private int GetNextByVar(int state, int var)
{
int ac = parserAutomaton.GetActionsCount(state, var);
for (int i = 0; i != ac; i++)
{
LRAction action = parserAutomaton.GetAction(state, var, i);
if (action.Code == LRActionCode.Shift)
{
return(action.Data);
}
}
return(0xFFFF);
}
/// <summary>
/// Gets the expected terminals for the specified state
/// </summary>
/// <param name="state">The DFA state</param>
/// <param name="terminals">The possible terminals</param>
/// <returns>The expected terminals</returns>
public LRExpected GetExpected(int state, ROList <Symbol> terminals)
{
LRExpected result = new LRExpected();
int offset = ncols * state;
for (int i = 0; i != terminals.Count; i++)
{
LRAction action = table[offset];
if (action.Code == LRActionCode.Shift)
{
result.Shifts.Add(terminals[i]);
}
else if (action.Code == LRActionCode.Reduce)
{
result.Reductions.Add(terminals[i]);
}
offset++;
}
return(result);
}
/// <summary>
/// Initializes a new automaton from the given binary stream
/// </summary>
/// <param name="reader">The binary stream to load from</param>
public RNGLRAutomaton(BinaryReader reader)
{
axiom = reader.ReadUInt16();
ncols = reader.ReadUInt16();
nstates = reader.ReadUInt16();
int nactions = (int)reader.ReadUInt32();
int nprod = reader.ReadUInt16();
int nnprod = reader.ReadUInt16();
columns = new ColumnMap();
for (int i = 0; i != ncols; i++)
{
columns.Add(reader.ReadUInt16(), i);
}
contexts = new LRContexts[nstates];
for (int i = 0; i != nstates; i++)
{
contexts[i] = new LRContexts(reader);
}
table = new Cell[nstates * ncols];
for (int i = 0; i != table.Length; i++)
{
table[i] = new Cell(reader);
}
actions = new LRAction[nactions];
for (int i = 0; i != nactions; i++)
{
actions[i] = new LRAction(reader);
}
productions = new LRProduction[nprod];
for (int i = 0; i != nprod; i++)
{
productions[i] = new LRProduction(reader);
}
nullables = new ushort[nnprod];
for (int i = 0; i != nnprod; i++)
{
nullables[i] = reader.ReadUInt16();
}
}
/// <summary>
/// Gets the expected terminals for the specified state
/// </summary>
/// <param name="state">The DFA state</param>
/// <param name="terminals">The possible terminals</param>
/// <returns>The expected terminals</returns>
public LRExpected GetExpected(int state, ROList <Symbol> terminals)
{
LRExpected result = new LRExpected();
for (int i = 0; i != terminals.Count; i++)
{
Cell cell = table[state * ncols + i];
for (int j = 0; j != cell.ActionsCount; j++)
{
LRAction action = actions[cell.ActionsIndex + j];
if (action.Code == LRActionCode.Shift)
{
result.AddUniqueShift(terminals[i]);
}
else if (action.Code == LRActionCode.Reduce)
{
result.AddUniqueReduction(terminals[i]);
}
}
}
return(result);
}
/// <summary>
/// Parses on the specified token kernel
/// </summary>
/// <param name="kernel">The token kernel to parse on</param>
/// <returns>The LR action that was used</returns>
private LRActionCode ParseOnToken(Lexer.TokenKernel kernel)
{
while (true)
{
LRAction action = automaton.GetAction(stack[head], kernel.TerminalID);
if (action.Code == LRActionCode.Shift)
{
head++;
if (head == stack.Length)
{
Array.Resize(ref stack, stack.Length + INIT_STACK_SIZE);
Array.Resize(ref stackIDs, stackIDs.Length + INIT_STACK_SIZE);
}
stack[head] = action.Data;
stackIDs[head] = kernel.TerminalID;
builder.StackPushToken(kernel.Index);
return(action.Code);
}
if (action.Code == LRActionCode.Reduce)
{
LRProduction production = automaton.GetProduction(action.Data);
head -= production.ReductionLength;
Reduce(production);
action = automaton.GetAction(stack[head], symVariables[production.Head].ID);
head++;
if (head == stack.Length)
{
Array.Resize(ref stack, stack.Length + INIT_STACK_SIZE);
Array.Resize(ref stackIDs, stackIDs.Length + INIT_STACK_SIZE);
}
stack[head] = action.Data;
stackIDs[head] = symVariables[production.Head].ID;
continue;
}
return(action.Code);
}
}
/// <summary>
/// Checks whether the specified terminal is indeed expected for a reduction
/// </summary>
/// <param name="terminal">The terminal to check</param>
/// <returns><code>true</code> if the terminal is really expected</returns>
/// <remarks>
/// This check is required because in the case of a base LALR graph,
/// some terminals expected for reduction in the automaton are coming from other paths.
/// </remarks>
private bool CheckIsExpected(Symbol terminal)
{
// copy the stack to use for the simulation
int[] myStack = new int[stack.Length];
Array.Copy(stack, myStack, head + 1);
int myHead = head;
// get the action for the stack's head
LRAction action = automaton.GetAction(myStack[myHead], terminal.ID);
while (action.Code != LRActionCode.None)
{
if (action.Code == LRActionCode.Shift)
{
// yep, the terminal was expected
return(true);
}
if (action.Code == LRActionCode.Reduce)
{
// execute the reduction
LRProduction production = automaton.GetProduction(action.Data);
myHead -= production.ReductionLength;
// this must be a shift
action = automaton.GetAction(myStack[myHead], symVariables[production.Head].ID);
myHead++;
if (myHead == myStack.Length)
{
Array.Resize(ref myStack, myStack.Length + INIT_STACK_SIZE);
}
myStack[myHead] = action.Data;
// now, get the new action for the terminal
action = automaton.GetAction(action.Data, terminal.ID);
}
}
// nope, that was a pathological case in a LALR graph
return(false);
}
/// <summary>
/// Gets the priority of the specified context required by the specified terminal
/// The priority is a positive integer. The lesser the value the higher the priority.
/// A value of -1 represents the unavailability of the required context.
/// </summary>
/// <param name="context">A context</param>
/// <param name="onTerminalID">The identifier of the terminal requiring the context</param>
/// <returns>The context priority, or -1 if the context is unavailable</returns>
public int GetContextPriority(int context, int onTerminalID)
{
// the default context is always active
if (context == Automaton.DEFAULT_CONTEXT)
{
return(int.MaxValue);
}
if (lexer.tokens.Size == 0)
{
// this is the first token, does it open the context?
return(automaton.GetContexts(0).Opens(onTerminalID, context) ? 0 : -1);
}
// retrieve the action for this terminal
LRAction action = automaton.GetAction(stack[head], onTerminalID);
// if the terminal is unexpected, do not validate
if (action.Code == LRActionCode.None)
{
return(-1);
}
// does the context opens with the terminal?
if (action.Code == LRActionCode.Shift && automaton.GetContexts(stack[head]).Opens(onTerminalID, context))
{
return(0);
}
LRProduction production = (action.Code == LRActionCode.Reduce) ? automaton.GetProduction(action.Data) : null;
// look into the stack for the opening of the context
for (int i = head - 1; i != -1; i--)
{
if (automaton.GetContexts(stack[i]).Opens(stackIDs[i + 1], context))
{
// the context opens here
// but is it closed by the reduction (if any)?
if (production == null || i < head - production.ReductionLength)
{
// no, we are still in the context
return(head - i);
}
}
}
// at this point, the requested context is not yet open or is closed by a reduction
// now, if the action is something else than a reduction (shift, accept or error), the context can never be produced
// for the context to open, a new state must be pushed onto the stack
// this means that the provided terminal must trigger a chain of at least one reduction
if (action.Code != LRActionCode.Reduce)
{
return(-1);
}
// there is at least one reduction, simulate
int[] myStack = new int[stack.Length];
Array.Copy(stack, myStack, head + 1);
int myHead = head;
while (action.Code == LRActionCode.Reduce)
{
// execute the reduction
production = automaton.GetProduction(action.Data);
myHead -= production.ReductionLength;
// this must be a shift
action = automaton.GetAction(myStack[myHead], symVariables[production.Head].ID);
myHead++;
if (myHead == myStack.Length)
{
Array.Resize(ref myStack, myStack.Length + INIT_STACK_SIZE);
}
myStack[myHead] = action.Data;
// now, get the new action for the terminal
action = automaton.GetAction(action.Data, onTerminalID);
}
// is this a shift action that opens the context?
return((action.Code == LRActionCode.Shift && automaton.GetContexts(myStack[myHead]).Opens(onTerminalID, context)) ? 0 : -1);
}
/// <summary>
/// Executes a reduction operation for a given path
/// </summary>
/// <param name="generation">The current GSS generation</param>
/// <param name="reduction">The reduction operation</param>
/// <param name="path">The GSS path to use for the reduction</param>
private void ExecuteReduction(int generation, Reduction reduction, GSSPath path)
{
// Get the rule's head
Symbol head = symVariables[reduction.prod.Head];
// Resolve the sub-root
int label = sppf.GetLabelFor(path.Generation, new TableElemRef(TableType.Variable, reduction.prod.Head));
if (label == SPPF.EPSILON)
{
// not in history, build the SPPF here
label = BuildSPPF(generation, reduction.prod, reduction.first, path);
}
// Get the target state by transition on the rule's head
int to = GetNextByVar(gss.GetRepresentedState(path.Last), head.ID);
// Find a node for the target state in the GSS
int w = gss.FindNode(generation, to);
if (w != -1)
{
// A node for the target state is already in the GSS
if (!gss.HasEdge(generation, w, path.Last))
{
// But the new edge does not exist
gss.CreateEdge(w, path.Last, label);
// Look for the new reductions at this state
if (reduction.prod.ReductionLength != 0)
{
int count = parserAutomaton.GetActionsCount(to, nextToken.TerminalID);
for (int i = 0; i != count; i++)
{
LRAction action = parserAutomaton.GetAction(to, nextToken.TerminalID, i);
if (action.Code == LRActionCode.Reduce)
{
LRProduction prod = parserAutomaton.GetProduction(action.Data);
// length 0 reduction are not considered here because they already exist at this point
if (prod.ReductionLength != 0)
{
reductions.Enqueue(new Reduction(path.Last, prod, label));
}
}
}
}
}
}
else
{
// Create the new corresponding node in the GSS
w = gss.CreateNode(to);
gss.CreateEdge(w, path.Last, label);
// Look for all the reductions and shifts at this state
int count = parserAutomaton.GetActionsCount(to, nextToken.TerminalID);
for (int i = 0; i != count; i++)
{
LRAction action = parserAutomaton.GetAction(to, nextToken.TerminalID, i);
if (action.Code == LRActionCode.Shift)
{
shifts.Enqueue(new Shift(w, action.Data));
}
else if (action.Code == LRActionCode.Reduce)
{
LRProduction prod = parserAutomaton.GetProduction(action.Data);
if (prod.ReductionLength == 0)
{
reductions.Enqueue(new Reduction(w, prod, SPPF.EPSILON));
}
else if (reduction.prod.ReductionLength != 0)
{
reductions.Enqueue(new Reduction(path.Last, prod, label));
}
}
}
}
}
/// <summary>
/// Checks whether the specified terminal is indeed expected for a reduction
/// </summary>
/// <param name="gssNode">The GSS node from which to reduce</param>
/// <param name="terminal">The terminal to check</param>
/// <returns><code>true</code> if the terminal is really expected</returns>
/// <remarks>
/// This check is required because in the case of a base LALR graph,
/// some terminals expected for reduction in the automaton are coming from other paths.
/// </remarks>
private bool CheckIsExpected(int gssNode, Symbol terminal)
{
// queue of GLR states to inspect:
List <int> queueGSSHead = new List <int>(); // the related GSS head
List <int[]> queueVStack = new List <int[]>(); // the virtual stack
// first reduction
{
int count = parserAutomaton.GetActionsCount(gss.GetRepresentedState(gssNode), terminal.ID);
for (int j = 0; j != count; j++)
{
LRAction action = parserAutomaton.GetAction(gss.GetRepresentedState(gssNode), terminal.ID, j);
if (action.Code == LRActionCode.Reduce)
{
// execute the reduction
LRProduction production = parserAutomaton.GetProduction(action.Data);
int nbPaths;
GSSPath[] paths = gss.GetPaths(gssNode, production.ReductionLength, out nbPaths);
for (int k = 0; k != nbPaths; k++)
{
GSSPath path = paths[k];
// get the target GLR state
int next = GetNextByVar(gss.GetRepresentedState(path.Last), symVariables[production.Head].ID);
// enqueue the info, top GSS stack node and target GLR state
queueGSSHead.Add(path.Last);
queueVStack.Add(new[] { next });
}
}
}
}
// now, close the queue
for (int i = 0; i != queueGSSHead.Count; i++)
{
int head = queueVStack[i][queueVStack[i].Length - 1];
int count = parserAutomaton.GetActionsCount(head, terminal.ID);
if (count == 0)
{
continue;
}
for (int j = 0; j != count; j++)
{
LRAction action = parserAutomaton.GetAction(head, terminal.ID, j);
if (action.Code == LRActionCode.Shift)
{
// yep, the terminal was expected
return(true);
}
if (action.Code == LRActionCode.Reduce)
{
// execute the reduction
LRProduction production = parserAutomaton.GetProduction(action.Data);
if (production.ReductionLength == 0)
{
// 0-length reduction => start from the current head
int[] virtualStack = new int[queueVStack[i].Length + 1];
Array.Copy(queueVStack[i], virtualStack, queueVStack[i].Length);
virtualStack[virtualStack.Length - 1] = GetNextByVar(head, symVariables[production.Head].ID);
// enqueue
queueGSSHead.Add(queueGSSHead[i]);
queueVStack.Add(virtualStack);
}
else if (production.ReductionLength < queueVStack[i].Length)
{
// we are still the virtual stack
int[] virtualStack = new int[queueVStack[i].Length - production.ReductionLength + 1];
Array.Copy(queueVStack[i], virtualStack, virtualStack.Length - 1);
virtualStack[virtualStack.Length - 1] = GetNextByVar(virtualStack[virtualStack.Length - 2], symVariables[production.Head].ID);
// enqueue
queueGSSHead.Add(queueGSSHead[i]);
queueVStack.Add(virtualStack);
}
else
{
// we reach the GSS
int nbPaths;
GSSPath[] paths = gss.GetPaths(queueGSSHead[i], production.ReductionLength - queueVStack[i].Length, out nbPaths);
for (int k = 0; k != nbPaths; k++)
{
GSSPath path = paths[k];
// get the target GLR state
int next = GetNextByVar(gss.GetRepresentedState(path.Last), symVariables[production.Head].ID);
// enqueue the info, top GSS stack node and target GLR state
queueGSSHead.Add(path.Last);
queueVStack.Add(new[] { next });
}
}
}
}
}
// nope, that was a pathological case in a LALR graph
return(false);
}
/// <summary>
/// Gets the priority of the specified context required by the specified terminal
/// The priority is a positive integer. The lesser the value the higher the priority.
/// A value of -1 represents the unavailability of the required context.
/// </summary>
/// <param name="context">A context</param>
/// <param name="onTerminalID">The identifier of the terminal requiring the context</param>
/// <returns>The context priority, or -1 if the context is unavailable</returns>
public int GetContextPriority(int context, int onTerminalID)
{
// the default context is always active
if (context == Automaton.DEFAULT_CONTEXT)
{
return(int.MaxValue);
}
if (lexer.tokens.Size == 0)
{
// this is the first token, does it open the context?
return(parserAutomaton.GetContexts(0).Opens(onTerminalID, context) ? 0 : -1);
}
// try to only look at stack heads that expect the terminal
List <int> queue = new List <int>();
List <LRProduction> productions = new List <LRProduction>();
List <int> distances = new List <int>();
bool foundOnPreviousShift = false;
foreach (Shift shift in shifts)
{
int count = parserAutomaton.GetActionsCount(shift.to, onTerminalID);
if (count == 0)
{
continue;
}
for (int i = 0; i != count; i++)
{
LRAction action = parserAutomaton.GetAction(shift.to, onTerminalID, i);
if (action.Code == LRActionCode.Shift)
{
// does the context opens with the terminal?
if (parserAutomaton.GetContexts(shift.to).Opens(onTerminalID, context))
{
return(0);
}
// looking at the immediate history, does the context opens from the shift just before?
if (parserAutomaton.GetContexts(gss.GetRepresentedState(shift.from)).Opens(nextToken.TerminalID, context))
{
foundOnPreviousShift = true;
break;
}
// no, enqueue
if (!queue.Contains(shift.from))
{
queue.Add(shift.from);
productions.Add(null);
distances.Add(2);
}
}
else
{
// this is reduction
LRProduction production = parserAutomaton.GetProduction(action.Data);
// looking at the immediate history, does the context opens from the shift just before?
if (parserAutomaton.GetContexts(gss.GetRepresentedState(shift.from)).Opens(nextToken.TerminalID, context))
{
if (production.ReductionLength < 1)
{
// the reduction does not close the context
foundOnPreviousShift = true;
break;
}
}
// no, enqueue
if (!queue.Contains(shift.from))
{
queue.Add(shift.from);
productions.Add(production);
distances.Add(2);
}
}
}
}
if (foundOnPreviousShift)
{
// found the context opening on the previous shift (and was not immediately closed by a reduction)
return(1);
}
if (queue.Count == 0)
{
// the track is empty, the terminal is unexpected
return(-1);
}
// explore the current GSS to find the specified context
for (int i = 0; i != queue.Count; i++)
{
int count;
GSSPath[] paths = gss.GetPaths(queue[i], 1, out count);
for (int p = 0; p != count; p++)
{
int from = paths[p].Last;
int symbolID = sppf.GetSymbolOn(paths[p][0]).ID;
int distance = distances[i];
LRProduction production = productions[i];
// was the context opened on this transition?
if (parserAutomaton.GetContexts(gss.GetRepresentedState(from)).Opens(symbolID, context))
{
if (production == null || production.ReductionLength < distance)
{
return(distance);
}
}
// no, enqueue
if (!queue.Contains(from))
{
queue.Add(from);
productions.Add(production);
distances.Add(distance + 1);
}
}
}
// at this point, the requested context is not yet open
// can it be open by a token with the specified terminal ID?
// queue of GLR states to inspect:
List <int> queueGSSHead = new List <int>(); // the related GSS head
List <int[]> queueVStack = new List <int[]>(); // the virtual stack
// first reduction
foreach (Shift shift in shifts)
{
int count = parserAutomaton.GetActionsCount(shift.to, onTerminalID);
if (count > 0)
{
// enqueue the info, top GSS stack node and target GLR state
queueGSSHead.Add(shift.from);
queueVStack.Add(new[] { shift.to });
}
}
// now, close the queue
for (int i = 0; i != queueGSSHead.Count; i++)
{
int head = queueVStack[i][queueVStack[i].Length - 1];
int count = parserAutomaton.GetActionsCount(head, onTerminalID);
if (count == 0)
{
continue;
}
for (int j = 0; j != count; j++)
{
LRAction action = parserAutomaton.GetAction(head, onTerminalID, j);
if (action.Code != LRActionCode.Reduce)
{
continue;
}
// execute the reduction
LRProduction production = parserAutomaton.GetProduction(action.Data);
if (production.ReductionLength == 0)
{
// 0-length reduction => start from the current head
int[] virtualStack = new int[queueVStack[i].Length + 1];
Array.Copy(queueVStack[i], virtualStack, queueVStack[i].Length);
int next = GetNextByVar(head, symVariables[production.Head].ID);
virtualStack[virtualStack.Length - 1] = next;
// enqueue
queueGSSHead.Add(queueGSSHead[i]);
queueVStack.Add(virtualStack);
}
else if (production.ReductionLength < queueVStack[i].Length)
{
// we are still the virtual stack
int[] virtualStack = new int[queueVStack[i].Length - production.ReductionLength + 1];
Array.Copy(queueVStack[i], virtualStack, virtualStack.Length - 1);
int next = GetNextByVar(virtualStack[virtualStack.Length - 2], symVariables[production.Head].ID);
virtualStack[virtualStack.Length - 1] = next;
// enqueue
queueGSSHead.Add(queueGSSHead[i]);
queueVStack.Add(virtualStack);
}
else
{
// we reach the GSS
int nbPaths;
GSSPath[] paths = gss.GetPaths(queueGSSHead[i], production.ReductionLength - queueVStack[i].Length, out nbPaths);
for (int k = 0; k != nbPaths; k++)
{
GSSPath path = paths[k];
// get the target GLR state
int next = GetNextByVar(gss.GetRepresentedState(path.Last), symVariables[production.Head].ID);
// enqueue the info, top GSS stack node and target GLR state
queueGSSHead.Add(path.Last);
queueVStack.Add(new[] { next });
}
}
}
}
foreach (int[] vstack in queueVStack)
{
int state = vstack[vstack.Length - 1];
int count = parserAutomaton.GetActionsCount(state, onTerminalID);
for (int i = 0; i != count; i++)
{
LRAction action = parserAutomaton.GetAction(state, onTerminalID, i);
if (action.Code == LRActionCode.Shift && parserAutomaton.GetContexts(state).Opens(onTerminalID, context))
{
// the context opens here
return(0);
}
}
}
// the context is still unavailable
return(-1);
}
