/// <summary>
/// 计算文法的所有单个的结点的FIRST
/// </summary>
/// <param name="grammar"></param>
/// <param name="nullableDict"></param>
/// <returns></returns>
private static void GetFirstCollection4Node(
this RegulationList grammar,
out FIRSTCollection firstCollection,
Dictionary <TreeNodeType, bool> nullableDict = null)
{
// 初始化FIRST
firstCollection = new FIRSTCollection();
// 初始化非叶结点的FIRST
foreach (var item in grammar.GetAllTreeNodeNonLeaveTypes())
{
if (nullableDict[item])
{
firstCollection.TryInsert(new FIRST(item, TreeNodeType.NullNode));
}
else
{
firstCollection.TryInsert(new FIRST(item));
}
}
// 初始化叶结点的FIRST（叶结点的FIRST实际上已经完工）
foreach (var item in grammar.GetAllTreeNodeLeaveTypes())
{
firstCollection.TryInsert(new FIRST(item, item));
}
bool changed = false;
do
{
changed = false;
foreach (var regulation in grammar)
{
FIRST first = FindFirst(firstCollection, regulation.Left);
int rightPartCount = regulation.RightPart.Count();
for (int checkCount = 0; checkCount < rightPartCount; checkCount++)
{
// 如果前面checkCount个结点都可为null，
// 就说明RightPart[checkCount]的FIRST是此regulation.Left的FIRST的一部分。
if (Nullable(regulation.RightPart, 0, checkCount, nullableDict))
{
FIRST refFirst = FindFirst(firstCollection, regulation.RightNode(checkCount));
if (refFirst == null)
{
throw new Exception("algorithm error!");
}
if (refFirst != first)
{
foreach (var value in refFirst.Values)
{
if (value != TreeNodeType.NullNode)
{
changed = first.TryInsert(value) || changed;
}
}
}
}
}
}
} while (changed);
}
/// <summary>
/// 根据文法和已经计算的所有结点的FIRST集，计算任意一个结点串的FIRST。
/// </summary>
/// <param name="grammar"></param>
/// <param name="firstList4Node"></param>
/// <param name="target"></param>
/// <returns></returns>
private static FIRST GetFirst(this RegulationList grammar, FIRSTCollection firstList4Node, Dictionary <TreeNodeType, bool> nullableDict, List <TreeNodeType> target)
{
// 初始化FIRST集
FIRST first = new FIRST(target);
bool changed = false;
do
{
changed = false;
int count = first.Target.Count();
for (int checkCount = 0; checkCount < count; checkCount++)
{
// 如果前i个结点都可为null，就说明下一个结点（first.Target[i]）的FIRST是此RightPart的FIRST的一部分
if (Nullable(first.Target, 0, checkCount, nullableDict))
{
// 找到下一个结点的FIRST
FIRST refFirst = FindFirst(firstList4Node, first.GetNode(checkCount));
foreach (var value in refFirst.Values)
{
if (value != TreeNodeType.NullNode)
{
changed = first.TryInsert(value) || changed;
}
}
}
}
{
// 如果RightPart的全部结点都可为null，就说明此RightPart的FIRST包含"null"结点。
if (Nullable(first.Target, 0, first.Target.Count(), nullableDict))
{
//throw new Exception("如果是在LR1分析器生成工具的设计时走到此处，说明代码有问题。");
if (!first.Values.Contains(TreeNodeType.NullNode))
{
changed = first.TryInsert(TreeNodeType.NullNode) || changed;
}
}
}
} while (changed);
return(first);
}