22 lines
824 B
C#
22 lines
824 B
C#
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using CanonSharp.Combinator.Abstractions;
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namespace CanonSharp.Combinator.Parsers.Bases;
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/// <summary>
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/// 选择解析器
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/// 如果第一个不成功则调用第二个
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/// </summary>
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/// <param name="first">第一个解析器</param>
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/// <param name="second">第二个解析器</param>
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/// <typeparam name="TToken">输入流类型</typeparam>
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/// <typeparam name="T">解析器结果类型</typeparam>
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internal sealed class AlternativeParser<TToken, T>(Parser<TToken, T> first, Parser<TToken, T> second)
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: Parser<TToken, T>
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{
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internal override ParseResult<TToken, TResult> Run<TState, TResult>(TState state,
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Func<ParseResult<TToken, T>, ParseResult<TToken, TResult>> continuation)
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{
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return first.Run(state, result => result.CaseOf(continuation, _ => second.Run(state, continuation)));
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}
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}
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