/// <summary>
/// 判定给定的候选式能否推导出ε（空）
/// </summary>
/// <param name="candidate"></param>
/// <returns></returns>
public bool CanInferNull(ProductionNodeList candidate)
{
foreach (var node in candidate)
{
if (node.Position == EnumProductionNodePosition.Leave)
{
if (node != ProductionNode.tail_null)
{
return(false);
}
}
else if (node.Position == EnumProductionNodePosition.Unknown)
{
throw new Exception(string.Format("文法中存在不合法的候选式{0}", candidate));
}
}
foreach (var node in candidate)
{
if (node == ProductionNode.tail_null)
{
continue;
}
var production = this.GetProduction(node);
//AppendSpaces(builder, prefixSpace);
//builder.AppendLine(string.Format("parse next production: {0}", production));
if (!this.CanInferNull(production))
{
return(false);
}
}
return(true);
}
/// <summary>
/// 7 <VOpt> ::= <V> <VOpt>;
/// <para>8 <VOpt> ::= "|" <V> <VOpt>;</para>
/// <para>9 <VOpt ::= null;</para>
/// </summary>
/// <param name="vlist"></param>
/// <param name="candidate"></param>
/// <param name="syntaxTree"></param>
private static object GetGrammarVOpt(RightSection vlist,
ProductionNodeList candidate, SyntaxTree <EnumTokenTypeCG, EnumVTypeCG, TreeNodeValueCG> syntaxTree)
{//<VOpt> ::= <V> <VOpt> | "|" <V> <VOpt> | null; // 7 8 9
if (syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VOpt___tail_nullLeave() ||
syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VOpt___tail_identifierLeave() ||
syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VOpt___tail_numberLeave() ||
syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VOpt___tail_constStringLeave() ||
syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VOpt___constStringLeave() ||
syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VOpt___tail_lessThan_Leave()
)
{
var v = GetGrammarV(syntaxTree.Children[0]);
candidate.Add(v);
return(GetGrammarVOpt(vlist, candidate, syntaxTree.Children[1]));
}
else if (syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VOpt___tail_or_Leave())
{
ProductionNodeList newCandidate = new ProductionNodeList();
vlist.Add(newCandidate);
var v = GetGrammarV(syntaxTree.Children[1]);
newCandidate.Add(v);
return(GetGrammarVOpt(vlist, newCandidate, syntaxTree.Children[2]));
}
else if (syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VOpt___tail_semicolon_Leave())
{
return(GetGrammarnull(syntaxTree.Children[0]));
}
else
{
return(string.Format("{0}", syntaxTree.CandidateFunc.ToString()));
}
}
/// <summary>
/// 获取此产生式结点列表（候选式）的复制品
/// </summary>
/// <returns></returns>
public object Clone()
{
var result = new ProductionNodeList();
result.AddRange(
from item in this
select(item.Clone() as ProductionNode));
return(result);
}
public object GetEnumVTypeSGItem(ProductionNodeList productionNodeList)
{
var result = new StringBuilder();
foreach (var item in productionNodeList)
{
result.Append(GetEnumVTypeSGItem(item));
}
return result.ToString();
}
/// <summary>
/// 获取与候选式对应的FIRST集的项
/// </summary>
/// <param name="candidate"></param>
/// <returns></returns>
public FIRSTCollectionItem GetItem(ProductionNodeList candidate)
{
foreach (var item in this)
{
if (item.ObjectiveCandidate == candidate)
{
return(item);
}
}
return(null);
}
/// <summary>
/// 获取推导式
/// </summary>
/// <param name="left">左部</param>
/// <param name="right">右部</param>
public Derivation(ProductionNode left, ProductionNodeList right)
{
if (left != null)
{
this.Left = left;
}
if (right != null)
{
this.Right = right;
}
}
/// <summary>
/// 判定此产生式右部是否包含给定的候选式
/// </summary>
/// <param name="candidate"></param>
/// <returns></returns>
public bool Contains(ProductionNodeList candidate)
{
if (candidate == null)
{
return(false);
}
foreach (var originalCandidate in this.RightCollection)
{
if (originalCandidate.Equals(candidate))
{
return(true);
}
}
return(false);
}
/// <summary>
/// From
/// </summary>
/// <param name="xDerivation"></param>
/// <returns></returns>
public static Derivation From(XElement xDerivation)
{
if (xDerivation == null)
{
return(null);
}
if (xDerivation.Name != strDerivation)
{
return(null);
}
var result = new Derivation();
result.Left = ProductionNode.From(xDerivation.Element(strLeft));
result.Right = ProductionNodeList.From(xDerivation.Element(strRight));
return(result);
}
/// <summary>
/// From
/// </summary>
/// <param name="xProductionNodeList"></param>
/// <returns></returns>
public static ProductionNodeList From(XElement xProductionNodeList)
{
if (xProductionNodeList == null)
{
return(null);
}
if (xProductionNodeList.Name != strCandidate)
{
return(null);
}
var result = new ProductionNodeList();
result.AddRange(
from item in xProductionNodeList.Elements(ProductionNode.strProductionNode)
select ProductionNode.From(item)
);
return(result);
}
/// <summary>
/// 4 <VList> ::= <V> <VOpt>;
/// </summary>
/// <param name="syntaxTree"></param>
private static RightSection GetGrammarVList(SyntaxTree <EnumTokenTypeCG, EnumVTypeCG, TreeNodeValueCG> syntaxTree)
{//<VList> ::= <V> <VOpt>; 4
RightSection vlist = new RightSection();
if (syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VList___constStringLeave() ||
syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VList___tail_constStringLeave() ||
syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VList___tail_identifierLeave() ||
syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VList___tail_lessThan_Leave() ||
syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VList___tail_nullLeave() ||
syntaxTree.CandidateFunc == LL1SyntaxParserCG.GetFuncParsecase_VList___tail_numberLeave())
{
var candidate = new ProductionNodeList();
vlist.Add(candidate);
var v = GetGrammarV(syntaxTree.Children[0]);
candidate.Add(v);
var info = GetGrammarVOpt(vlist, candidate, syntaxTree.Children[1]);
}
return(vlist);
}
/// <summary>
/// 创建一个文法的FIRST集中的一项
/// <para>一项也是一个集合，其元素为产生式结点（只有叶结点）</para>
/// </summary>
/// <param name="candiate">指向的候选式</param>
/// <param name="production">指向的产生式</param>
/// <param name="grammar">指向的文法</param>
public FIRSTCollectionItem(ProductionNodeList candiate, ContextfreeProduction production, ContextfreeGrammar grammar)
{
this.m_ObjectiveCandidate = candiate;
this.m_ObjectiveProduction = production;
this.m_ObjectiveGrammar = grammar;
}
