82 lines
2.8 KiB
C#
82 lines
2.8 KiB
C#
using Canon.Core.Enums;
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using Canon.Core.GrammarParser;
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using Canon.Core.LexicalParser;
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using Canon.Core.SyntaxNodes;
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namespace Canon.Core.Abstractions;
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/// <summary>
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/// 语法分析器接口
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/// </summary>
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public interface IGrammarParser
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{
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public ITransformer BeginTransformer { get; }
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public NonTerminator Begin { get; }
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/// <summary>
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/// 分析指定的词法记号流并构建对应的语法树
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/// </summary>
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/// <param name="tokens">输入的词法记号流</param>
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/// <returns>语法树的根节点</returns>
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/// <exception cref="InvalidOperationException">语法分析错误</exception>
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public ProgramStruct Analyse(IEnumerable<SemanticToken> tokens)
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{
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Stack<AnalyseState> stack = [];
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stack.Push(new AnalyseState(BeginTransformer, SyntaxNodeBase.Create(SemanticToken.End)));
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using IEnumerator<SemanticToken> enumerator = tokens.GetEnumerator();
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if (!enumerator.MoveNext())
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{
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throw new InvalidOperationException("Input token list is empty");
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}
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while (true)
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{
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AnalyseState top = stack.Peek();
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// 首先尝试进行归约
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if (top.State.ReduceTable.TryGetValue(enumerator.Current, out ReduceInformation? information))
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{
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if (information.Left == Begin)
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{
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// 如果是归约到起始符
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// 那么就直接返回不继续进行归约
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return top.Node.Convert<ProgramStruct>();
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}
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List<SyntaxNodeBase> children = [];
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NonTerminatorType leftType = information.Left.Type;
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for (int i = 0; i < information.Length; i++)
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{
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children.Add(stack.Pop().Node);
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}
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// 为了符合生成式的顺序而倒序
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children.Reverse();
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stack.Push(new AnalyseState(stack.Peek().State.ShiftTable[information.Left],
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SyntaxNodeBase.Create(leftType, children)));
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continue;
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}
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// 如果没有成功归约就进行移进
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if (top.State.ShiftTable.TryGetValue(enumerator.Current, out ITransformer? next))
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{
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stack.Push(new AnalyseState(next, SyntaxNodeBase.Create(enumerator.Current)));
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if (enumerator.MoveNext())
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{
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continue;
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}
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else
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{
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throw new InvalidOperationException("Run out of token but not accept");
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}
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}
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throw new InvalidOperationException("Failed to analyse input grammar");
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}
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}
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private record AnalyseState(ITransformer State, SyntaxNodeBase Node);
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}
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