/// <summary>
/// この要素の先頭にくる可能性のある終端記号群を返します．
/// </summary>
/// <param name="generator"></param>
/// <returns></returns>
public IList <string> GetFirstTerminals(ScriptParserGenerator generator)
{
if (_firstTerminals != null)
{
return(new ReadOnlyCollection <string>(_firstTerminals));
}
HashSet <string> ret = new HashSet <string>();
HashSet <string> dependencies = new HashSet <string>();
Queue <string> dependencyCandidates = new Queue <string>();
string[] subDeps;
foreach (string first in this.GetFirstTerminalsOfSelf(out subDeps))
{
ret.Add(first);
}
foreach (string dep in subDeps)
{
dependencyCandidates.Enqueue(dep);
}
while (dependencyCandidates.Count > 0)
{
string dep = dependencyCandidates.Dequeue();
if (dependencies.Contains(dep))
{
continue;
}
dependencies.Add(dep);
DefinitionElement depDef = generator.LookUpDefinition(dep);
IList <string> firsts = depDef.GetFirstTerminalsOfSelf(out subDeps);
foreach (string subDep in subDeps)
{
dependencyCandidates.Enqueue(subDep);
}
foreach (string first in firsts)
{
ret.Add(first);
}
}
if (ret.Contains(null))
{
ret.RemoveWhere(r => r == null);
ret.Add(null);
}
_firstTerminals = ret.ToArray();
return(new ReadOnlyCollection <string>(_firstTerminals));
}
/// <summary>
/// この定義に後続する終端記号を返します．
/// </summary>
/// <param name="generator"></param>
/// <returns></returns>
public IList <string> GetFollowingTerminals(ScriptParserGenerator generator)
{
generator.InitializeFollowingTerminals();
if (_followingTerminals != null)
{
return(new ReadOnlyCollection <string>(_followingTerminals));
}
List <string> ret = new List <string>(_followingTerminalsOfSelf.Where(f => f != null));
// 循環対策のために一時的に入れておく
_followingTerminals = ret.ToArray();
foreach (string dependency in _followingDependencies)
{
DefinitionElement def = generator.LookUpDefinition(dependency);
ret.AddRange(def.GetFollowingTerminals(generator));
}
_followingTerminals = ret.Distinct().ToArray();
return(new ReadOnlyCollection <string>(_followingTerminals));
}
protected override void SetupFollowingTerminalsOfSelf(ScriptParserGenerator generator, string[] followings)
{
switch (_literal.Type)
{
case GeneratorLexType.Terminal:
break;
case GeneratorLexType.Nonterminal:
DefinitionElement def = generator.LookUpDefinition(this.InnerWord);
def.AddFollowingTerminals(followings);
if (followings.Contains(null))
{
def.AddNonterminalContainingThisAtTail(this.RootDefinition.DefinitionName);
}
break;
default:
throw new NotSupportedException();
}
}