add: 抽象语法树节点 (#5)

fix:
- Expression格式化过程中如果Pos在最右边就不显示
- Expression中不考虑Pos

Reviewed-on: PostGuard/Canon#5

Canon.Core/GrammarParser/Expression.cs

@@ -24,7 +24,7 @@ public class Expression : IEquatable<Expression>
     /// <summary>
     /// 当前移进的位置
     /// </summary>
-    public int Pos { get; set; }
+    public required int Pos { get; init; }
 
     public bool Equals(Expression? other)
     {
@@ -52,7 +52,8 @@ public class Expression : IEquatable<Expression>
         }
 
         return Left == other.Left
-               && LookAhead == other.LookAhead;
+               && LookAhead == other.LookAhead
+               && Pos == other.Pos;
     }
 
     public override bool Equals(object? obj)
@@ -69,6 +70,7 @@ public class Expression : IEquatable<Expression>
     {
         int hash = Left.GetHashCode();
         hash ^= LookAhead.GetHashCode();
+        hash ^= Pos.GetHashCode();
 
         foreach (TerminatorBase terminator in Right)
         {
@@ -93,6 +95,11 @@ public class Expression : IEquatable<Expression>
             result += Right[i].ToString();
         }
 
+        if (Pos == Right.Count)
+        {
+            result += '~';
+        }
+
         result += $", {LookAhead}";
 
         return result;

Canon.Core/GrammarParser/Grammar.cs

@@ -8,10 +8,10 @@ public class Grammar
 
     public required LrState BeginState { get; init; }
 
-    public void Analyse(IEnumerable<SemanticToken> tokens)
+    public SyntaxNode Analyse(IEnumerable<SemanticToken> tokens)
     {
-        Stack<LrState> stack = [];
-        stack.Push(BeginState);
+        Stack<AnalyseState> stack = [];
+        stack.Push(new AnalyseState(BeginState, new SyntaxNode(SemanticToken.End)));
 
         using IEnumerator<SemanticToken> enumerator = tokens.GetEnumerator();
         if (!enumerator.MoveNext())
@@ -21,11 +21,11 @@ public class Grammar
 
         while (true)
         {
-            LrState top = stack.Peek();
+            AnalyseState top = stack.Peek();
 
             // 尝试进行移进
             bool acceptFlag = false, reduceFlag = false;
-            foreach (Expression e in top.Expressions)
+            foreach (Expression e in top.State.Expressions)
             {
                 if (e.Pos == e.Right.Count && e.LookAhead == enumerator.Current)
                 {
@@ -36,21 +36,24 @@ public class Grammar
                     else
                     {
                         reduceFlag = true;
+                        SyntaxNode newNode = new(e.Left.Type);
 
                         for (int i = 0; i < e.Right.Count; i++)
                         {
-                            stack.Pop();
+                            newNode.Children.Add(stack.Pop().Node);
                         }
 
-                        stack.Push(stack.Peek().Transformer[e.Left]);
+                        stack.Push(new AnalyseState(stack.Peek().State.Transformer[e.Left],
+                            newNode));
                     }
+                    break;
                 }
             }
 
             if (acceptFlag)
             {
                 // 接受文法 退出循环
-                break;
+                return top.Node;
             }
 
             if (reduceFlag)
@@ -60,9 +63,9 @@ public class Grammar
             }
 
             // 尝试进行移进
-            if (top.Transformer.TryGetValue(enumerator.Current, out LrState? next))
+            if (top.State.Transformer.TryGetValue(enumerator.Current, out LrState? next))
             {
-                stack.Push(next);
+                stack.Push(new AnalyseState(next, new SyntaxNode(enumerator.Current)));
                 if (enumerator.MoveNext())
                 {
                     continue;
@@ -76,4 +79,6 @@ public class Grammar
             throw new InvalidOperationException("Failed to analyse input grammar");
         }
     }
+
+    private record AnalyseState(LrState State, SyntaxNode Node);
 }

Canon.Core/GrammarParser/GrammarBuilder.cs

@@ -177,7 +177,7 @@ public class GrammarBuilder
                     {
                         Expression newExpression = new()
                         {
-                            Left = nonTerminator, Right = nextExpression, LookAhead = lookAhead
+                            Left = nonTerminator, Right = nextExpression, LookAhead = lookAhead, Pos = 0
                         };
 
                         if (!closure.Contains(newExpression))
@@ -207,7 +207,7 @@ public class GrammarBuilder
 
         Expression begin = new()
         {
-            Left = Begin, Right = Generators[Begin].First(), LookAhead = Terminator.EndTerminator
+            Left = Begin, Right = Generators[Begin].First(), LookAhead = Terminator.EndTerminator, Pos = 0
         };
 
         LrState beginState = new() { Expressions = CalculateClosure(begin) };
@@ -235,9 +235,8 @@ public class GrammarBuilder
                     TerminatorBase next = e.Right[e.Pos];
                     Expression nextExpression = new()
                     {
-                        Left = e.Left, Right = e.Right, LookAhead = e.LookAhead, Pos = e.Pos
+                        Left = e.Left, Right = e.Right, LookAhead = e.LookAhead, Pos = e.Pos + 1
                     };
-                    nextExpression.Pos += 1;
 
                     if (!nextExpressions.TryAdd(next, [nextExpression]))
                     {

Canon.Core/GrammarParser/SyntaxNode.cs

@@ -0,0 +1,130 @@
+using System.Collections;
+using Canon.Core.Enums;
+using Canon.Core.LexicalParser;
+
+namespace Canon.Core.GrammarParser;
+
+/// <summary>
+/// 抽象语法树上的节点
+/// </summary>
+public class SyntaxNode : IEquatable<SyntaxNode>, IEnumerable<SyntaxNode>
+{
+    private readonly SemanticToken? _semanticToken;
+    private readonly NonTerminatorType _nonTerminatorType;
+
+    public bool IsTerminated { get; }
+
+    public List<SyntaxNode> Children { get; } = [];
+
+    public SyntaxNode(SemanticToken token)
+    {
+        IsTerminated = true;
+        _semanticToken = token;
+    }
+
+    public SyntaxNode(NonTerminatorType nonTerminatorType)
+    {
+        IsTerminated = false;
+        _nonTerminatorType = nonTerminatorType;
+    }
+
+    /// <summary>
+    /// 获得终结节点包含的记号对象
+    /// </summary>
+    /// <returns>词法分析得到的记号对象</returns>
+    /// <exception cref="InvalidOperationException">在非终结节点上调用该方法</exception>
+    public SemanticToken GetSemanticToken()
+    {
+        if (!IsTerminated)
+        {
+            throw new InvalidOperationException("Can not get semantic token from a not terminated node");
+        }
+
+        return _semanticToken!;
+    }
+
+    /// <summary>
+    /// 获得非终结节点的类型
+    /// </summary>
+    /// <returns>非终结节点类型</returns>
+    /// <exception cref="InvalidOperationException">在终结节点上调用该方法</exception>
+    public NonTerminatorType GetNonTerminatorType()
+    {
+        if (IsTerminated)
+        {
+            throw new InvalidOperationException("Can not get non terminated type from a terminated node");
+        }
+
+        return _nonTerminatorType;
+    }
+
+    public IEnumerator<SyntaxNode> GetEnumerator()
+    {
+        yield return this;
+
+        foreach (SyntaxNode child in Children)
+        {
+            foreach (SyntaxNode node in child)
+            {
+                yield return node;
+            }
+        }
+    }
+
+    public bool Equals(SyntaxNode? other)
+    {
+        if (other is null)
+        {
+            return false;
+        }
+
+        if (IsTerminated != other.IsTerminated)
+        {
+            return false;
+        }
+
+        if (IsTerminated)
+        {
+            return GetSemanticToken() == other.GetSemanticToken();
+        }
+        else
+        {
+            // 在判等时是否需要判断子节点也相等？
+            return GetNonTerminatorType() == other.GetNonTerminatorType();
+        }
+    }
+
+    public override bool Equals(object? obj)
+    {
+        if (obj is not SyntaxNode other)
+        {
+            return false;
+        }
+
+        return Equals(other);
+    }
+
+    public override int GetHashCode()
+    {
+        if (IsTerminated)
+        {
+            return GetSemanticToken().GetHashCode();
+        }
+        else
+        {
+            return GetNonTerminatorType().GetHashCode();
+        }
+    }
+
+    IEnumerator IEnumerable.GetEnumerator() => GetEnumerator();
+
+    public static bool operator ==(SyntaxNode a, SyntaxNode b)
+    {
+        return a.Equals(b);
+    }
+
+    public static bool operator !=(SyntaxNode a, SyntaxNode b)
+    {
+        return !a.Equals(b);
+    }
+}

Canon.Core/GrammarParser/Terminator.cs

@@ -96,7 +96,7 @@ public class Terminator : TerminatorBase, IEquatable<Terminator>
             case SemanticTokenType.Delimiter:
                 return _delimiterType.ToString();
             default:
-                return _keywordType.ToString();
+                return _terminatorType.ToString();
         }
     }
 
@@ -189,23 +189,18 @@ public class Terminator : TerminatorBase, IEquatable<Terminator>
 /// <summary>
 /// 语法中的非终结符
 /// </summary>
-public class NonTerminator : TerminatorBase, IEquatable<NonTerminator>
+public class NonTerminator(NonTerminatorType type) : TerminatorBase, IEquatable<NonTerminator>
 {
     public override bool IsTerminated => false;
 
-    private readonly NonTerminatorType _type;
-
-    public NonTerminator(NonTerminatorType type)
-    {
-        _type = type;
-    }
+    public NonTerminatorType Type { get; } = type;
 
     public override int GetHashCode()
     {
-        return _type.GetHashCode();
+        return Type.GetHashCode();
     }
 
-    public override string ToString() => _type.ToString();
+    public override string ToString() => Type.ToString();
 
     public bool Equals(NonTerminator? other)
     {
@@ -214,7 +209,7 @@ public class NonTerminator : TerminatorBase, IEquatable<NonTerminator>
             return false;
         }
 
-        return _type == other._type;
+        return Type == other.Type;
     }
 
     public override bool Equals(object? obj)

Canon.Tests/GrammarParserTests/SimpleGrammarTests.cs

@@ -118,6 +118,7 @@ public class SimpleGrammarTests
         };
 
         Grammar grammar = builder.Build();
+        // n + n
         List<SemanticToken> tokens =
         [
             new IdentifierSemanticToken { LinePos = 0, CharacterPos = 0, LiteralValue = "n" },
@@ -129,7 +130,73 @@ public class SimpleGrammarTests
             SemanticToken.End
         ];
 
-        // 验证分析语句不会抛出错误
-        grammar.Analyse(tokens);
+        // 分析树为
+        //        E
+        //        |
+        //       /\
+        //     / | \
+        //    E  +  T
+        //    |     |
+        //    T     F
+        //    |     |
+        //   F     n
+        //   |
+        //   n
+        SyntaxNode root = grammar.Analyse(tokens);
+        Assert.Equal(NonTerminatorType.ProgramStruct, root.GetNonTerminatorType());
+        Assert.Equal(3, root.Children.Count);
+        Assert.Contains(root.Children, node =>
+        {
+            if (node.IsTerminated && node.GetSemanticToken().TokenType == SemanticTokenType.Operator)
+            {
+                OperatorSemanticToken token = (OperatorSemanticToken)node.GetSemanticToken();
+
+                return token.OperatorType == OperatorType.Plus;
+            }
+
+            return false;
+        });
+        Assert.Equal(9, root.Count());
+    }
+
+    [Fact]
+    public void AnalyseComplexSentenceTest()
+    {
+        GrammarBuilder builder = new()
+        {
+            Generators = s_simpleGrammar, Begin = new NonTerminator(NonTerminatorType.StartNonTerminator)
+        };
+
+        Grammar grammar = builder.Build();
+        // (n + n) * n
+        List<SemanticToken> tokens =
+        [
+            new DelimiterSemanticToken
+            {
+                LinePos = 0, CharacterPos = 0, LiteralValue = "(", DelimiterType = DelimiterType.LeftParenthesis
+            },
+            new IdentifierSemanticToken { LinePos = 0, CharacterPos = 0, LiteralValue = "n" },
+            new OperatorSemanticToken
+            {
+                LinePos = 0, CharacterPos = 0, LiteralValue = "+", OperatorType = OperatorType.Plus
+            },
+            new IdentifierSemanticToken { LinePos = 0, CharacterPos = 0, LiteralValue = "n" },
+            new DelimiterSemanticToken
+            {
+                LinePos = 0, CharacterPos = 0, LiteralValue = ")", DelimiterType = DelimiterType.RightParenthesis
+            },
+            new OperatorSemanticToken
+            {
+                LinePos = 0, CharacterPos = 0, LiteralValue = "*", OperatorType = OperatorType.Multiply
+            },
+            new IdentifierSemanticToken { LinePos = 0, CharacterPos = 0, LiteralValue = "n" },
+            SemanticToken.End
+        ];
+
+        SyntaxNode root = grammar.Analyse(tokens);
+        Assert.Equal(18, root.Count());
+        Assert.False(root.IsTerminated);
+        Assert.Equal(NonTerminatorType.ProgramStruct, root.GetNonTerminatorType());
+        Assert.Single(root.Children);
     }
 }