22 lines
986 B
C#
22 lines
986 B
C#
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using CanonSharp.Combinator.Abstractions;
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namespace CanonSharp.Combinator.Parsers.Modifiers;
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/// <summary>
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/// 向前看解析器
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/// 使用传入的解析器向前解析
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/// 但是返回的结果中输入流读取状态不前移
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/// </summary>
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/// <param name="parser">需要向前看的解析器</param>
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/// <typeparam name="TToken">输入流令牌</typeparam>
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/// <typeparam name="T">返回的解析结果类型</typeparam>
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internal sealed class LookAheadParser<TToken, T>(Parser<TToken, T> parser) : ModifiedParser<TToken, T, T>(parser)
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{
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protected override ParseResult<TToken, T> Succeed<TState>(TState state,
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SuccessfulResult<TToken, T> successfulResult)
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=> ParseResultBuilder.Succeed<TToken, TState, T>(successfulResult.Value, state);
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protected override ParseResult<TToken, T> Fail<TState>(TState state, FailedResult<TToken, T> failedResult)
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=> ParseResultBuilder.Fail<TToken, TState, T>($"Failed when looking ahead: {failedResult}", state);
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}
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