public void Restart()
{
currentLALR = lrStates.InitialState;
sysPosition.Column = 0;
sysPosition.Line = 0;
CurrentPosition.Line = 0;
CurrentPosition.Column = 0;
haveReduction = false;
ExpectedSymbols.Clear();
inputTokens.Clear();
stack.Clear();
lookaheadBuffer = "";
groupStack.Clear();
}
// This function analyzes a token and either:
// 1. Makes a SINGLE reduction and pushes a complete Reduction object on the m_Stack
// 2. Accepts the token and shifts
// 3. Errors and places the expected symbol indexes in the Tokens list
// The Token is assumed to be valid and WILL be checked
// If an action is performed that requires controlt to be returned to the user, the function returns true.
// The Message parameter is then set to the type of action.
private ParseResult ParseLALR(ref Token token)
{
LRAction parseAction = lrStates[currentLALR][token.Parent];
ParseResult parseResult = 0;
if (parseAction != null)
{
haveReduction = false;
switch (parseAction.Type)
{
case LRActionType.Shift:
currentLALR = parseAction.Value;
token.State = (short)currentLALR;
stack.Push(token);
parseResult = ParseResult.Shift;
break;
case LRActionType.Reduce:
Production production = ProductionTable[parseAction.Value];
Token head;
// The current rule only consists of a single nonterminal and can be trimmed from the
// parse tree. Usually we create a new Reduction, assign it to the Data property
// of Head and push it on the m_Stack. However, in this case, the Data property of the
// Head will be assigned the Data property of the reduced token (i.e. the only one
// on the m_Stack).
// In this case, to save code, the value popped of the m_Stack is changed into the head.
if (TrimReductions && production.ContainsOneNonTerminal())
{
head = stack.Pop();
head.Parent = production.Head;
parseResult = ParseResult.ReduceEliminated;
}
else
{
haveReduction = true;
Reduction newReduction = new Reduction(production.Handle.Count())
{
Parent = production
};
short n = (short)(production.Handle.Count() - 1);
while (n >= 0)
{
newReduction[n] = stack.Pop();
n--;
}
head = new Token(production.Head, newReduction);
parseResult = ParseResult.ReduceNormal;
}
short index = stack.Peek().State;
short n2 = lrStates[index].IndexOf(production.Head);
if (n2 != -1)
{
currentLALR = lrStates[index][n2].Value;
head.State = (short)currentLALR;
stack.Push(head);
break;
}
parseResult = ParseResult.InternalError;
break;
case LRActionType.Accept:
haveReduction = true;
parseResult = ParseResult.Accept;
break;
}
}
else
{
ExpectedSymbols.Clear();
foreach (LRAction LRAction in lrStates[currentLALR])
{
switch (LRAction.Symbol.Type)
{
case SymbolType.Content:
case SymbolType.End:
case SymbolType.GroupStart:
case SymbolType.GroupEnd:
ExpectedSymbols.Add(LRAction.Symbol);
break;
}
}
parseResult = ParseResult.SyntaxError;
}
return(parseResult);
}
