private bool step()
{
if (currentToken == null)
{
int pos = 0;
if (previousToken != null)
{
pos = previousToken.Position + previousToken.Lexeme.Length;
}
currentToken = new Token(DOLLAR, "$", pos);
}
int x = ((int)stack.Pop());
int a = currentToken.Id;
if (x == EPSILON)
{
return(false);
}
else if (isTerminal(x))
{
if (x == a)
{
if (stack.Count == 0)
{
return(true);
}
else
{
previousToken = currentToken;
currentToken = scanner.nextToken();
return(false);
}
}
else
{
throw new SyntaticError(parserConst.PARSER_ERROR[x], currentToken.Position);
}
}
else if (isNonTerminal(x))
{
if (pushProduction(x, a))
{
return(false);
}
else
{
throw new SyntaticError(parserConst.PARSER_ERROR[x], currentToken.Position);
}
}
else // isSemanticAction(x)
{
semanticAnalyser.executeAction(x - parserConst.FIRST_SEMANTIC_ACTION, previousToken);
return(false);
}
}
