feat: Parser Combinator库和词法分析器 (#2)

Reviewed-on: https://git.bupt-hpc.cn/jackfiled/CanonSharp/pulls/2
Co-authored-by: jackfiled <xcrenchangjun@outlook.com>
Co-committed-by: jackfiled <xcrenchangjun@outlook.com>

CanonSharp.Combinator/Parsers/ModifiedParser.cs

@@ -0,0 +1,27 @@
+using CanonSharp.Combinator.Abstractions;
+
+namespace CanonSharp.Combinator.Parsers;
+
+/// <summary>
+/// 修改解析器返回结果的解析器基类
+/// </summary>
+/// <param name="parser">需要修改结果的解析器</param>
+/// <typeparam name="TToken">输入流类型</typeparam>
+/// <typeparam name="TIntermediate">需要修改结果的解析器</typeparam>
+/// <typeparam name="T">最终返回的解析结果</typeparam>
+public abstract class ModifiedParser<TToken, TIntermediate, T>(Parser<TToken, TIntermediate> parser) : Parser<TToken, T>
+{
+    protected abstract ParseResult<TToken, T> Fail<TState>(TState state,
+        FailedResult<TToken, TIntermediate> failedResult)
+        where TState : IReadState<TToken, TState>;
+
+    protected abstract ParseResult<TToken, T> Succeed<TState>(TState state,
+        SuccessfulResult<TToken, TIntermediate> successfulResult)
+        where TState : IReadState<TToken, TState>;
+
+    internal override ParseResult<TToken, TResult> Run<TState, TResult>(TState state,
+        Func<ParseResult<TToken, T>, ParseResult<TToken, TResult>> continuation)
+        => parser.Run(state, result => result.CaseOf(
+            success => continuation(Succeed(state, success)),
+            failure => continuation(Fail(state, failure))));
+}