/// <summary>
/// Yields success when the specified <paramref name="parser"/> does not match.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TResult">The type of the elements that are generated from parsing the source elements.</typeparam>
/// <param name="parser">The parser for which any match results in failure.</param>
/// <returns>A parser that yields failure when the specified <paramref name="parser"/> matches or
/// an empty sequence to indicate success when it does not match.</returns>
public static IObservableParser <TSource, IObservable <TResult> > None <TSource, TResult>(
this IObservableParser <TSource, TResult> parser)
{
Contract.Requires(parser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, IObservable <TResult> > >() != null);
if (parser is IObservableParserCursor <TSource> )
{
return(parser.AtEndOfSequence());
}
else
{
return(parser.Yield <TSource, TResult, IObservable <TResult> >(
"None",
(source, observer) =>
{
return parser.Parse(source).Any().SubscribeSafe(
any =>
{
if (!any)
{
observer.OnNext(ObservableParseResult.SuccessMany <TResult>(length: 0));
}
},
observer.OnError,
observer.OnCompleted);
}));
}
}