/// <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 IParser <TSource, IEnumerable <TResult> > None <TSource, TResult>(
this IParser <TSource, TResult> parser)
{
Contract.Requires(parser != null);
Contract.Ensures(Contract.Result <IParser <TSource, IEnumerable <TResult> > >() != null);
if (parser is IParserCursor <TSource> )
{
return(parser.AtEndOfSequence());
}
else
{
return(parser.Yield(
"None",
source =>
parser.Parse(source).Any()
? ParseResult.ReturnFailureMany <TResult>()
: ParseResult.ReturnSuccessMany <TResult>(length: 0)));
}
}
/// <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>
/// <typeparam name="TSuccess">The type of the success value.</typeparam>
/// <param name="parser">The parser for which any match results in failure.</param>
/// <param name="successResult">The value that is yielded if the specified <paramref name="parser"/> does not match.</param>
/// <returns>A parser that yields failure when the specified <paramref name="parser"/> matches or success when
/// it does not match.</returns>
public static IParser <TSource, TSuccess> None <TSource, TResult, TSuccess>(
this IParser <TSource, TResult> parser,
TSuccess successResult)
{
Contract.Requires(parser != null);
Contract.Ensures(Contract.Result <IParser <TSource, TSuccess> >() != null);
if (parser is IParserCursor <TSource> )
{
return(parser.AtEndOfSequence(successResult));
}
else
{
return(parser.Yield(
"None",
source =>
parser.Parse(source).Any()
? ParseResult.ReturnFailure <TSuccess>()
: ParseResult.Return(successResult, length: 0)));
}
}