/// <summary>Adds an new LRAction to this table.</summary> /// <param name="p_symbol">The Symbol.</param> /// <param name="p_action">The Action.</param> /// <param name="p_value">The value.</param> public void AddItem(Symbol p_symbol, Action p_action, int p_value) { LRAction item = new LRAction(); item.Symbol = p_symbol; item.Action = p_action; item.Value = p_value; m_members.Add(item); }
/// <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); }
/// This function analyzes a token and either: /// 1. Makes a SINGLE reduction and pushes a complete Reduction object on the 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 private ParseResult ParseToken(Token p_token) { ParseResult result = ParseResult.InternalError; LRActionTable table = m_LalrTables[m_LalrState]; LRAction action = table.GetActionForSymbol(p_token.TableIndex); if (action != null) { m_haveReduction = false; m_outputTokens.Clear(); switch (action.Action) { case Action.Accept: m_haveReduction = true; result = ParseResult.Accept; break; case Action.Shift: p_token.State = m_LalrState = action.Value; m_tempStack.PushToken(p_token); result = ParseResult.Shift; break; case Action.Reduce: result = Reduce(m_rules[action.Value]); break; } } else { // syntax error - fill expected tokens. m_outputTokens.Clear(); foreach (LRAction a in table.Members) { SymbolType kind = a.Symbol.Kind; if (kind == SymbolType.Terminal || kind == SymbolType.End) { m_outputTokens.PushToken(new Token(a.Symbol)); } } result = ParseResult.SyntaxError; } return(result); }