/// <summary>Produces a reduction.</summary>
/// <remarks>Removes as many tokens as members in the rule and pushes a
/// non-terminal token.</remarks>
private ParseResult Reduce(Rule p_rule)
{
ParseResult result;
Token head;
if (m_trimReductions && p_rule.ContainsOneNonTerminal)
{
// 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 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 stack). In this case, to save code, the value popped of the stack is changed
// into the head.
head = m_tempStack.PopToken();
head.SetParent(p_rule.RuleNonTerminal);
result = ParseResult.ReduceEliminated;
}
else
{
Reduction reduction = new Reduction();
reduction.ParentRule = p_rule;
m_tempStack.PopTokensInto(reduction, p_rule.SymbolCount);
head = new Token();
head.Data = reduction;
head.SetParent(p_rule.RuleNonTerminal);
m_haveReduction = true;
result = ParseResult.ReduceNormal;
}
int index = m_tempStack.PeekToken().State;
LRAction action = m_LalrTables[index].GetActionForSymbol(p_rule.RuleNonTerminal.TableIndex);
if (action != null)
{
head.State = m_LalrState = action.Value;;
m_tempStack.PushToken(head);
}
else
{
throw new ParserException("Action for LALR state is null");
}
return(result);
}
/// Pops the next token from the internal input queue.
public Token PopInputToken()
{
return(m_inputTokens.PopToken());
}