/// <summary>
/// Matches the left parser followed by the right parser, but only returns the left parser's matches.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TIgnore">The type of the elements that are generated by the right parser.</typeparam>
/// <typeparam name="TResult">The type of the elements that are generated by the left parser.</typeparam>
/// <param name="parser">The parser from which to yield matches.</param>
/// <param name="ignoreParser">The parser from which to ignore matches.</param>
/// <returns>A parser that matches the left parser followed by the right parser, but only returns the
/// left parser's matches.</returns>
public static IObservableParser <TSource, TResult> IgnoreTrailing <TSource, TIgnore, TResult>(
this IObservableParser <TSource, TResult> parser,
IObservableParser <TSource, TIgnore> ignoreParser)
{
Contract.Requires(parser != null);
Contract.Requires(ignoreParser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.SelectMany(_ => ignoreParser, (leading, _) => leading));
}