From 94622f5796227fe6772887f171e17834cfe685bc Mon Sep 17 00:00:00 2001
From: jackfiled <xcrenchangjun@outlook.com>
Date: Sun, 10 Mar 2024 11:22:19 +0800
Subject: [PATCH] add: LrState

---
 Canon.Core/GrammarParser/Expression.cs | 16 ++++++-
 Canon.Core/GrammarParser/LrState.cs    | 66 ++++++++++++++++++++++++++
 2 files changed, 80 insertions(+), 2 deletions(-)
 create mode 100644 Canon.Core/GrammarParser/LrState.cs

diff --git a/Canon.Core/GrammarParser/Expression.cs b/Canon.Core/GrammarParser/Expression.cs
index 096163f..980f0ef 100644
--- a/Canon.Core/GrammarParser/Expression.cs
+++ b/Canon.Core/GrammarParser/Expression.cs
@@ -1,17 +1,29 @@
 namespace Canon.Core.GrammarParser;
 
 /// <summary>
-/// An expression in the LR, like 'program_struct -> ~program_head ; program_body.'
-/// The '~' is the shift position now.
+/// LR语法中的一个表达式，例如 'program_struct -> ~program_head ; program_body'
+/// 其中'~'标识当前移进到达的位置
 /// </summary>
 public class Expression : IEquatable<Expression>
 {
+    /// <summary>
+    /// 表达式的左部
+    /// </summary>
     public required NonTerminator Left { get; init; }
 
+    /// <summary>
+    /// 表达式的向前看字符串
+    /// </summary>
     public required Terminator LookAhead { get; init; }
 
+    /// <summary>
+    /// 表达式的右部
+    /// </summary>
     public required List<TerminatorBase> Right { get; init; }
 
+    /// <summary>
+    /// 当前移进的位置
+    /// </summary>
     public int Pos { get; set; }
 
     public bool Equals(Expression? other)
diff --git a/Canon.Core/GrammarParser/LrState.cs b/Canon.Core/GrammarParser/LrState.cs
new file mode 100644
index 0000000..b5ffb65
--- /dev/null
+++ b/Canon.Core/GrammarParser/LrState.cs
@@ -0,0 +1,66 @@
+namespace Canon.Core.GrammarParser;
+
+/// <summary>
+/// LR语法中的一个项目集规范族
+/// 也就是自动机中的一个状态
+/// </summary>
+public class LrState : IEquatable<LrState>
+{
+    /// <summary>
+    /// 项目集规范族
+    /// </summary>
+    public required HashSet<Expression> Expressions { get; init; }
+
+    /// <summary>
+    /// 自动机的迁移规则
+    /// </summary>
+    public Dictionary<TerminatorBase, LrState> Transformer { get; } = [];
+
+    public bool Equals(LrState? other)
+    {
+        if (other is null)
+        {
+            return false;
+        }
+
+        if (Expressions.Count != other.Expressions.Count)
+        {
+            return false;
+        }
+
+        // 如果两个集合的大小相等，且一个是另一个的子集，那么两个集合相等。
+        return Expressions.IsSubsetOf(other.Expressions);
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (obj is not LrState other)
+        {
+            return false;
+        }
+
+        return Equals(other);
+    }
+
+    public override int GetHashCode()
+    {
+        int hash = 0;
+
+        foreach (Expression expression in Expressions)
+        {
+            hash ^= expression.GetHashCode();
+        }
+
+        return hash;
+    }
+
+    public static bool operator ==(LrState a, LrState b)
+    {
+        return a.Equals(b);
+    }
+
+    public static bool operator !=(LrState a, LrState b)
+    {
+        return !a.Equals(b);
+    }
+}