/// <summary>
/// Select the result alternative which consumed the most amount of input and use that to
/// continue the parse. If there are no alternatives, returns failure. If there are ties,
/// the first is selected.
/// </summary>
/// <typeparam name="TInput"></typeparam>
/// <typeparam name="TOutput"></typeparam>
/// <param name="multiParser"></param>
/// <returns></returns>
public static IParser <TInput, TOutput> Longest <TInput, TOutput>(this IMultiParser <TInput, TOutput> multiParser)
=> multiParser.Select(args =>
{
var longest = args.Result.Results
.Where(r => r.Success)
.OrderByDescending(r => r.Consumed)
.FirstOrDefault();
return(longest != null ? args.Success(longest) : args.Failure());
});
/// <summary>
/// Returns the first successful alternative which matches a predicate to continue the
/// parse with.
/// </summary>
/// <typeparam name="TInput"></typeparam>
/// <typeparam name="TOutput"></typeparam>
/// <param name="multiParser"></param>
/// <param name="predicate"></param>
/// <returns></returns>
public static IParser <TInput, TOutput> First <TInput, TOutput>(this IMultiParser <TInput, TOutput> multiParser, Func <IResultAlternative <TOutput>, bool> predicate)
{
Assert.ArgumentNotNull(predicate, nameof(predicate));
return(multiParser.Select(args =>
{
var selected = args.Result.Results.FirstOrDefault(predicate);
return selected != null ? args.Success(selected) : args.Failure();
}));
}
/// <summary>
/// Expect the IMultiResult to contain exactly 1 alternative, and select that to continue.
/// </summary>
/// <typeparam name="TInput"></typeparam>
/// <typeparam name="TOutput"></typeparam>
/// <param name="multiParser"></param>
/// <returns></returns>
public static IParser <TInput, TOutput> Single <TInput, TOutput>(this IMultiParser <TInput, TOutput> multiParser)
=> multiParser.Select(args =>
{
if (args.Result.Results.Count == 1)
{
return(args.Success(args.Result.Results[0]));
}
return(args.Failure());
});
