/// <summary>
/// Matches zero or more values in between the specified <paramref name="open"/> and <paramref name="close"/> parsers.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TOpen">The type of the elements that are generated from parsing the <paramref name="open"/> elements.</typeparam>
/// <typeparam name="TClose">The type of the elements that are generated from parsing the <paramref name="close"/> elements.</typeparam>
/// <param name="open">The parser after which the group begins.</param>
/// <param name="close">The parser at which the group ends.</param>
/// <returns>A parser with a grammar that matches the <paramref name="open"/> parser, followed by everything up to the first
/// match of the <paramref name="close"/> parser, yielding the results in between.</returns>
public static IObservableParser <TSource, IObservable <TSource> > Group <TSource, TOpen, TClose>(
this IObservableParser <TSource, TOpen> open,
IObservableParser <TSource, TClose> close)
{
Contract.Requires(open != null);
Contract.Requires(close != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, IObservable <TSource> > >() != null);
return(open.Group(open.Next.Not(close).NoneOrMore(), close));
}