55 lines
2.1 KiB
C#
55 lines
2.1 KiB
C#
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namespace Parsley
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{
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using System;
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public static class ParserQuery
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{
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/// <summary>
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/// Converts any value into a parser that always succeeds with the given value in its reply.
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/// </summary>
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/// <remarks>
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/// In monadic terms, this is the 'Unit' function.
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/// </remarks>
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/// <typeparam name="T">The type of the value to treat as a parse result.</typeparam>
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/// <param name="value">The value to treat as a parse result.</param>
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public static Parser<T> SucceedWithThisValue<T>(this T value)
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{
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return new LambdaParser<T>(tokens => new Parsed<T>(value, tokens));
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}
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/// <summary>
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/// Allows LINQ syntax to construct a new parser from a simpler parser, using a single 'from' clause.
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/// </summary>
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public static Parser<U> Select<T, U>(this Parser<T> parser, Func<T, U> constructResult)
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{
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return parser.Bind(t => constructResult(t).SucceedWithThisValue());
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}
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/// <summary>
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/// Allows LINQ syntax to contruct a new parser from an ordered sequence of simpler parsers, using multiple 'from' clauses.
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/// </summary>
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public static Parser<V> SelectMany<T, U, V>(this Parser<T> parser, Func<T, Parser<U>> k, Func<T, U, V> s)
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{
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return parser.Bind(x => k(x).Bind(y => s(x, y).SucceedWithThisValue()));
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}
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/// <summary>
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/// Extend a parser such that, after executing, the remaining input is processed by the next parser in the chain.
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/// </summary>
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/// <remarks>
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/// In monadic terms, this is the 'Bind' function.
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/// </remarks>
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private static Parser<U> Bind<T, U>(this Parser<T> parser, Func<T, Parser<U>> constructNextParser)
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{
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return new LambdaParser<U>(tokens =>
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{
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var reply = parser.Parse(tokens);
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if (reply.Success)
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return constructNextParser(reply.Value).Parse(reply.UnparsedTokens);
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return new Error<U>(reply.UnparsedTokens, reply.ErrorMessages);
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});
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}
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}
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}
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