/// <summary>
/// Matches the specified <paramref name="parser"/> or yields the specified default result if there are
/// no matches.
/// </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 that might produce matches.</param>
/// <param name="defaultResult">The value that is yielded if the specified <paramref name="parser"/> does not match.</param>
/// <returns>A parser that yields matches from the specified <paramref name="parser"/> or the specified default result
/// if the <paramref name="parser"/> does not match.</returns>
public static IObservableParser <TSource, TResult> WithDefault <TSource, TResult>(
this IObservableParser <TSource, TResult> parser,
TResult defaultResult)
{
Contract.Requires(parser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield(
"WithDefault",
(source, observer) =>
{
bool hasResult = false;
return parser.Parse(source).SubscribeSafe(
result =>
{
hasResult = true;
observer.OnNext(result);
},
observer.OnError,
() =>
{
if (!hasResult)
{
observer.OnNext(ParseResult.Create(defaultResult, length: 0));
}
observer.OnCompleted();
});
}));
}
/// <summary>
/// Matches the specified <paramref name="parser"/> or yields success without a value when it does not match.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TResult">The type of the elements of the result sequences that are generated from parsing the source elements.</typeparam>
/// <param name="parser">The parser that might produce matches.</param>
/// <returns>A parser that yields matches from the specified <paramref name="parser"/> or
/// an empty observable sequence to indicate success when it does not match.</returns>
public static IObservableParser <TSource, IObservable <TResult> > Maybe <TSource, TResult>(
this IObservableParser <TSource, IObservable <TResult> > parser)
{
Contract.Requires(parser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, IObservable <TResult> > >() != null);
return(parser.Yield(
"Maybe",
(source, observer) =>
{
bool hasResult = false;
return parser.Parse(source).SubscribeSafe(
result =>
{
hasResult = true;
observer.OnNext(result);
},
observer.OnError,
() =>
{
if (!hasResult)
{
observer.OnNext(ObservableParseResult.SuccessMany <TResult>(length: 0));
}
observer.OnCompleted();
});
}));
}
/// <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);
}));
}
}
/// <summary>
/// Indicates a successful parse operation without actually parsing by yielding a single result containing an empty sequence.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TResult">The type of the elements in the sequences that are generated from parsing the source elements.</typeparam>
/// <param name="parser">The parser for which a single empty result sequence is returned to indicate success.</param>
/// <remarks>
/// <see cref="Success{TSource,TResult}(IObservableParser{TSource,IObservable{TResult}})"/> is required as an explicit overload
/// because the meaning of the parser's result sequence is special and must not be compounded into a sequence of sequences,
/// which would happen if the <see cref="Success{TSource,TResult}(IObservableParser{TSource,TResult})"/> overload were to be called
/// instead.
/// </remarks>
/// <returns>A parser that returns a single result containing an empty sequence with a length
/// of zero, starting from the index at which the specified <paramref name="parser"/> starts.</returns>
public static IObservableParser <TSource, IObservable <TResult> > Success <TSource, TResult>(
this IObservableParser <TSource, IObservable <TResult> > parser)
{
Contract.Requires(parser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, IObservable <TResult> > >() != null);
return(parser.Yield("Success", source => ObservableParseResult.ReturnSuccessMany <TResult>(length: 0)));
}
/// <summary>
/// Converts greedy matches from the specified <paramref name="parser"/> into matches that
/// have a length of zero.
/// </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 greedy parser to be made into a non-greedy parser.</param>
/// <returns>A parser that converts the greedy matches from the specified <paramref name="parser"/> into
/// matches that have a length of zero.</returns>
public static IObservableParser <TSource, TResult> NonGreedy <TSource, TResult>(
this IObservableParser <TSource, TResult> parser)
{
Contract.Requires(parser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield("NonGreedy", source => parser.Parse(source).Select(result => result.Yield(length: 0))));
}
/// <summary>
/// Projects each match from the specified <paramref name="parser"/> into a singleton observable sequence
/// that contains the match's value.
/// </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 from which matches will be projected into singleton observable sequences.</param>
/// <returns>A parser that yields matches from the specified <paramref name="parser"/> projected into singleton
/// observable sequences.</returns>
public static IObservableParser <TSource, IObservable <TResult> > Amplify <TSource, TResult>(
this IObservableParser <TSource, TResult> parser)
{
Contract.Requires(parser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, IObservable <TResult> > >() != null);
return(parser.Yield("Amplify", source => parser.Parse(source).Select(result => result.YieldMany())));
}
/// <summary>
/// Indicates a failure to parse without actually parsing by returning an empty sequence of parse results.
/// </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 that is to fail.</param>
/// <returns>A parser that always returns an empty sequence of parse results, starting from the index at which
/// the specified <paramref name="parser"/> starts.</returns>
public static IObservableParser <TSource, TResult> Failure <TSource, TResult>(
this IObservableParser <TSource, TResult> parser)
{
Contract.Requires(parser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield("Failure", source => ObservableParseResult.ReturnFailure <TResult>()));
}
/// <summary>
/// Invokes the specified <paramref name="action"/> on each result for its side-effects.
/// </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 from which results will be supplied to the specified <paramref name="action"/>.</param>
/// <param name="action">The method that will be called for each parser result.</param>
/// <returns>A new parser that is the same as the specified parser and also invokes the specified
/// <paramref name="action"/> with each result for its side-effects.</returns>
public static IObservableParser <TSource, TResult> OnSuccess <TSource, TResult>(
this IObservableParser <TSource, TResult> parser,
Action <IParseResult <TResult> > action)
{
Contract.Requires(parser != null);
Contract.Requires(action != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield("OnSuccess", source => parser.Parse(source).Do(action)));
}
/// <summary>
/// Projects matches from the specified <paramref name="parser"/> into a new form.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TIntermediate">The type of the elements that are generated from parsing the source elements.</typeparam>
/// <typeparam name="TResult">The type of the elements that are projected from the matches of the specified <paramref name="parser"/>.</typeparam>
/// <param name="parser">The parser from which matches will be projected by the specified <paramref name="selector"/> function.</param>
/// <param name="selector">A transform function to apply to each match.</param>
/// <returns>A parser that projects matches from the specified <paramref name="parser"/> into a new form.</returns>
public static IObservableParser <TSource, TResult> Select <TSource, TIntermediate, TResult>(
this IObservableParser <TSource, TIntermediate> parser,
Func <TIntermediate, TResult> selector)
{
Contract.Requires(parser != null);
Contract.Requires(selector != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield("Select", source => parser.Parse(source).Select(result => result.Yield(selector))));
}
/// <summary>
/// Matches everything in between the specified <paramref name="open"/> and <paramref name="close"/> parsers,
/// yielding the first unambiguous match as well as everything in between any sub-groups and overlapping groups,
/// extending past the unambiguous match of the <paramref name="close"/> parser, that match the same grammar.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <param name="open">The parser after which the group begins.</param>
/// <param name="close">The parser at which the group ends.</param>
/// <remarks>
/// The same <paramref name="open"/> or <paramref name="close"/> parser may produce multiple matches at the same index.
/// </remarks>
/// <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 as well as the results of all ambiguous
/// matches of the group grammar.</returns>
public static IObservableParser <TSource, IObservable <TSource> > AmbiguousGroup <TSource>(
this IObservableParser <TSource, TSource> open,
IObservableParser <TSource, TSource> close)
{
Contract.Requires(open != null);
Contract.Requires(close != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, IObservable <TSource> > >() != null);
return(open.Yield("AmbiguousGroup", source => AmbiguousGroupInternal(source, open, close)));
}
/// <summary>
/// Matches all results from the specified <paramref name="parser"/> for which the specified
/// <paramref name="predicate"/> returns <see langword="true"/>.
/// </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 from which matches will be filtered by the specified <paramref name="predicate"/>.</param>
/// <param name="predicate">A function that returns <see langword="true"/> to indicate when a match should be yielded and
/// <see langword="false"/> when a match should be ignored.</param>
/// <returns>A parser that matches only those results from the specified <paramref name="parser"/> for which
/// the specified <paramref name="predicate"/> returns <see langword="true"/>.</returns>
public static IObservableParser <TSource, TResult> Where <TSource, TResult>(
this IObservableParser <TSource, TResult> parser,
Func <TResult, bool> predicate)
{
Contract.Requires(parser != null);
Contract.Requires(predicate != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield("Where", source => parser.Parse(source).Where(result => predicate(result.Value))));
}
/// <summary>
/// Indicates a successful parse operation without actually parsing by yielding the specified scalar <paramref name="result"/>
/// with the specified length.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TIntermediate">The type of the elements that are generated from parsing the source elements.</typeparam>
/// <typeparam name="TResult">The type of the <paramref name="result"/>.</typeparam>
/// <param name="parser">The parser for which the specified <paramref name="result"/> indicates success.</param>
/// <param name="result">The value of the created parser's result.</param>
/// <param name="length">The length of the created parser's result.</param>
/// <returns>A parser that always returns the specified scalar <paramref name="result"/> with the specified
/// length, starting from the index at which the specified <paramref name="parser"/> starts.</returns>
public static IObservableParser <TSource, TResult> Success <TSource, TIntermediate, TResult>(
this IObservableParser <TSource, TIntermediate> parser,
TResult result,
int length)
{
Contract.Requires(parser != null);
Contract.Requires(length >= 0);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield("Success", source => ObservableParseResult.Return(result, length)));
}
/// <summary>
/// Projects each match from the specified <paramref name="parser"/> into another parser, merges all of the results
/// and transforms them with the result selector function.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TFirstResult">The type of the elements that are generated from parsing the source elements.</typeparam>
/// <typeparam name="TSecondResult">The type of the elements that are generated from the projected parsers.</typeparam>
/// <typeparam name="TResult">The type of the elements that are projected from the matches of the projected parsers.</typeparam>
/// <param name="parser">The parser from which each match is passed to the specified parser selector function to create
/// the next parser.</param>
/// <param name="parserSelector">A transform function to apply to each match from the first <paramref name="parser"/>.</param>
/// <param name="resultSelector">A transform function to apply to each match from the projected parsers.</param>
/// <returns>A parser that projects each match from the specified <paramref name="parser"/> into another parser,
/// merges all of the results and transforms them with the result selector function.</returns>
public static IObservableParser <TSource, TResult> SelectMany <TSource, TFirstResult, TSecondResult, TResult>(
this IObservableParser <TSource, TFirstResult> parser,
Func <TFirstResult, IObservableParser <TSource, TSecondResult> > parserSelector,
Func <TFirstResult, TSecondResult, TResult> resultSelector)
{
Contract.Requires(parser != null);
Contract.Requires(parserSelector != null);
Contract.Requires(resultSelector != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield("SelectMany", source => SelectManyInternal(source, parser, parserSelector, resultSelector)));
}
/// <summary>
/// Throws a <see cref="ParseException"/> returned by the specified function if 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 that must succeed otherwise a <see cref="ParseException"/> is thrown.</param>
/// <param name="exceptionFactory">A function that returns the <see cref="ParseException"/> to be thrown describing the
/// failed expectation.</param>
/// <returns>A parser that yields the matches from the specified <paramref name="parser"/> or throws
/// a <see cref="ParseException"/> returned by the specified functions if there are no matches.</returns>
public static IObservableParser <TSource, TResult> Required <TSource, TResult>(
this IObservableParser <TSource, TResult> parser,
Func <int, Exception> exceptionFactory)
{
Contract.Requires(parser != null);
Contract.Requires(exceptionFactory != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield(
"Required",
(source, observer) =>
{
int index = source.CurrentIndex;
bool hasResult = false;
return parser.Parse(source).SubscribeSafe(
result =>
{
hasResult = true;
observer.OnNext(result);
},
observer.OnError,
() =>
{
if (hasResult)
{
observer.OnCompleted();
}
else
{
Exception exception = exceptionFactory(index);
if (exception == null)
{
exception = new ParseException(index);
}
else if (!(exception is ParseException))
{
exception = new ParseException(index, exception);
}
#if !SILVERLIGHT && !PORT_45 && !PORT_40
ParserTraceSources.Input.TraceEvent(System.Diagnostics.TraceEventType.Error, 0, "{0}", exception);
#endif
observer.OnError(exception);
}
});
}));
}
/// <summary>
/// Projects each match from the specified <paramref name="parser"/> into an observable sequence, merges all of the results
/// and transforms them with the result selector function.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TFirstResult">The type of the elements that are generated from parsing the source elements.</typeparam>
/// <typeparam name="TCollection">The type of the elements in the sequences that are projected from the matches.</typeparam>
/// <typeparam name="TResult">The type of the elements that are projected from the projected sequences.</typeparam>
/// <param name="parser">The parser from which each match is passed to the specified collection selector function.</param>
/// <param name="collectionSelector">A transform function to apply to each match from the first <paramref name="parser"/>.</param>
/// <param name="resultSelector">A transform function to apply to each element from the projected sequences.</param>
/// <param name="lengthSelector">A function that returns the length for each pair of projected values.</param>
/// <returns>A parser that projects each match from the specified <paramref name="parser"/> into an observable sequence,
/// merges all of the results and transforms them with the result selector function.</returns>
public static IObservableParser <TSource, TResult> SelectMany <TSource, TFirstResult, TCollection, TResult>(
this IObservableParser <TSource, TFirstResult> parser,
Func <TFirstResult, IObservable <TCollection> > collectionSelector,
Func <TFirstResult, TCollection, TResult> resultSelector,
Func <IParseResult <TFirstResult>, TCollection, int> lengthSelector)
{
Contract.Requires(parser != null);
Contract.Requires(collectionSelector != null);
Contract.Requires(resultSelector != null);
Contract.Requires(lengthSelector != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield("SelectMany", source => SelectManyInternal(source, parser, collectionSelector, resultSelector, lengthSelector)));
}
/// <summary>
/// Yields success if the specified parser starts at the end of the input sequence.
/// </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 that provides the context in which to check whether the cursor is at the end of the input sequence.</param>
/// <param name="successResult">The value that is yielded if the specified parser starts at the end of the input sequence.</param>
/// <returns>A new parser that yields success without parsing if the cursor is positioned at the end of the input sequence; otherwise, yields no results.</returns>
public static IObservableParser <TSource, TSuccess> AtEndOfSequence <TSource, TResult, TSuccess>(
this IObservableParser <TSource, TResult> parser,
TSuccess successResult)
{
Contract.Requires(parser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TSuccess> >() != null);
return(parser.Yield <TSource, TResult, TSuccess>(
"AtEndOfSequence",
(source, observer) =>
{
IDisposable disposable;
if (source.IsSequenceTerminated)
{
if (source.AtEndOfSequence)
{
observer.OnNext(ParseResult.Create(successResult, length: 0));
}
observer.OnCompleted();
disposable = Disposable.Empty;
}
else
{
bool hasResult = false;
disposable = source.Subscribe(
Observer.Create <TSource>(
result => hasResult = true,
observer.OnError,
() =>
{
if (!hasResult)
{
Contract.Assume(source.AtEndOfSequence);
observer.OnNext(ParseResult.Create(successResult, length: 0));
}
observer.OnCompleted();
}),
count: 1);
}
return disposable;
}));
}
/// <summary>
/// Matches the specified <paramref name="parser"/> the specified number of times.
/// </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 to be matched.</param>
/// <param name="count">The specified number of times to match the specified <paramref name="parser"/>.</param>
/// <returns>A parser that matches the specified <paramref name="parser"/> the specified number of times.</returns>
public static IObservableParser <TSource, IObservable <TResult> > Exactly <TSource, TResult>(
this IObservableParser <TSource, TResult> parser,
int count)
{
Contract.Requires(parser != null);
Contract.Requires(count >= 0);
Contract.Ensures(Contract.Result <IObservableParser <TSource, IObservable <TResult> > >() != null);
if (count == 0)
{
return(parser.Yield(_ => ObservableParseResult.ReturnSuccessMany <TResult>(length: 0)));
}
else if (count == 1)
{
// Profiling has shown this to be about 50% faster than Repeat(parser, 1).All()
return(parser.Amplify());
}
else if (parser is IObservableParserCursor <TSource> )
{
/* Profiling has shown this to be exponentially faster in next.Exactly(largeN) queries for Ix.
* It hasn't been profiled in Rx, but I'm assuming that for similar reasons as Ix it would prove
* to be exponentially faster. Furthermore, due to the extra plumbing in Rx that's being avoided
* by this optimization, it may have even greater gains than Ix.
*/
return(parser.Yield <TSource, TResult, IObservable <TResult> >(
"Exactly",
source =>
from list in source.Take(count).ToList()
where list.Count == count
select ParseResult.Create(list.Cast <TResult>().ToObservable(Scheduler.Immediate), count)));
}
else
{
return(System.Linq.Enumerable.Repeat(parser, count).All());
}
}
/// <summary>
/// Applies an <paramref name="accumulator"/> function over each result sequence from the
/// specified <paramref name="parser"/> and yields a sequence of accumulated results.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TIntermediate">The type of the elements that are generated from parsing the source elements.</typeparam>
/// <typeparam name="TAccumulate">The type of the accumulation.</typeparam>
/// <typeparam name="TResult">The type of the elements that are generated from projecting the accumulation.</typeparam>
/// <param name="parser">The parser that produces a sequence of result sequences to be aggregated.</param>
/// <param name="seed">A function that returns the initial value of the accumulation for each parse result.</param>
/// <param name="accumulator">A function to be invoked on each element of each parse result.</param>
/// <param name="selector">A function that projects the final aggregation of each parse result.</param>
/// <returns>A parser that returns the aggregated results.</returns>
public static IObservableParser <TSource, TResult> Aggregate <TSource, TIntermediate, TAccumulate, TResult>(
this IObservableParser <TSource, IObservable <TIntermediate> > parser,
Func <TAccumulate> seed,
Func <TAccumulate, TIntermediate, TAccumulate> accumulator,
Func <TAccumulate, TResult> selector)
{
Contract.Requires(parser != null);
Contract.Requires(accumulator != null);
Contract.Requires(selector != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield(
"Aggregate",
source =>
from result in parser.Parse(source)
from acc in result.Value.Aggregate(seed(), accumulator)
select result.Yield(selector(acc))));
}
public static IObservableParser <TSource, TResult> OnFailure <TSource, TResult>(
this IObservableParser <TSource, TResult> parser,
Action action)
{
Contract.Requires(parser != null);
Contract.Requires(action != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield(
"OnFailure",
(source, observer) =>
{
bool hasResult = false;
return parser.Parse(source).Subscribe(
result =>
{
hasResult = true;
observer.OnNext(result);
},
observer.OnError,
() =>
{
if (!hasResult)
{
try
{
action();
}
catch (Exception ex)
{
observer.OnError(ex);
return;
}
}
observer.OnCompleted();
});
}));
}
/// <summary>
/// Matches the single element from the ambiguous result sequence in each match that is yielded by the specified
/// <paramref name="parser"/> and fails for any match in which there is zero or more than one element.
/// </summary>
/// <typeparam name="TSource">The type of the source elements.</typeparam>
/// <typeparam name="TResult">The type of the elements of the result sequences that are generated from parsing the source elements.</typeparam>
/// <param name="parser">The parser from which the single result element is yielded for each match.</param>
/// <returns>A parser that matches the single element from the result sequence of each match that is
/// yielded by the specified <paramref name="parser"/> and fails for any match in which there is zero
/// or more than one element.</returns>
public static IObservableParser <TSource, TResult> Single <TSource, TResult>(
this IObservableParser <TSource, IObservable <TResult> > parser)
{
Contract.Requires(parser != null);
Contract.Ensures(Contract.Result <IObservableParser <TSource, TResult> >() != null);
return(parser.Yield <TSource, IObservable <TResult>, TResult>(
"Single",
source => parser.Parse(source).SelectMany(
result => Observable.Create <IParseResult <TResult> >(
observer =>
{
bool hasResult = false;
TResult firstResult = default(TResult);
return result.Value.Take(2).Subscribe(
innerResult =>
{
if (!hasResult)
{
firstResult = innerResult;
hasResult = true;
}
else
{
hasResult = false;
}
},
observer.OnError,
() =>
{
if (hasResult)
{
observer.OnNext(result.Yield(firstResult));
}
observer.OnCompleted();
});
}))));
}
private static IObservableParser <TSource, IObservable <TResult> > AtLeast <TSource, TSeparator, TResult>(
this IObservableParser <TSource, TResult> parser,
string name,
int count,
int maximum = -1,
IObservableParser <TSource, TSeparator> separator = null,
bool nonGreedy = false)
{
Contract.Requires(parser != null);
Contract.Requires(!string.IsNullOrEmpty(name));
Contract.Requires(count >= 0);
Contract.Requires(maximum == -1 || maximum >= count);
Contract.Requires(maximum != 0);
Contract.Ensures(Contract.Result <IObservableParser <TSource, IObservable <TResult> > >() != null);
// TODO: Update this method to properly support multi-result parsers.
/* The current implementation just uses Math.Max for the lengths and aggregates all of the results into a single list.
* The correct behavior is more like a SelectMany query, so consider using the new SelectMany overload that AllObservableParser uses.
*/
/* This method is optimized to prevent stack overflows due to two factors: recursion and using Skip to move the source cursor.
*
* The previous implementation used recursive calls to NoneOrMore, in which there was a linear relationship between the number
* of stack frames and the number of elements in the input sequence. As an input sequence grew and the parser continued matching
* elements, the number of calls to the Skip operator (via the Remainder extension) grew linearly, and so did the number of branches
* due to NoneOrMore using the Or operator, which not only added the Or operator to the stack but added all of the calls to the
* quantified parser between the stack frames that Or added, for every subsequent element in the sequence that the parser matched.
*/
return(parser.Yield <TSource, TResult, IObservable <TResult> >(
name,
(source, observer) =>
{
Contract.Requires(source.IsForwardOnly);
var branch = source.Branch();
var list = new List <TResult>();
int total = 0;
int totalLength = 0;
Action onCompleted = () =>
{
if (total >= count)
{
observer.OnNext(new ParseResult <IObservable <TResult> >(list.ToObservable(Scheduler.Immediate), totalLength));
}
observer.OnCompleted();
};
var subscription = new SerialDisposable();
Func <IDisposable> start = () =>
Scheduler.Immediate.Schedule(self =>
{
bool hasResult = false;
bool hasSeparatorResult = false;
int length = 0;
int separatorLength = 0;
Action currentCompleted = () =>
{
if (hasResult)
{
totalLength += length + separatorLength;
if (total < (maximum == -1 ? count : maximum))
{
total++;
}
if (total != maximum && (separator == null || hasSeparatorResult))
{
if (nonGreedy && total >= count)
{
var lookAhead = new LookAheadParseResult <IObservable <TResult> >(list.ToObservable(Scheduler.Immediate), totalLength);
subscription.SetDisposableIndirectly(() => new CompositeDisposable(
lookAhead,
lookAhead.Subscribe(success =>
{
if (success)
{
onCompleted();
}
else
{
self();
}
})));
observer.OnNext(lookAhead);
return;
}
else
{
self();
return;
}
}
}
onCompleted();
};
subscription.SetDisposableIndirectly(() =>
parser.Parse(branch).SubscribeSafe(
result =>
{
hasResult = true;
length = Math.Max(length, result.Length);
list.Add(result.Value);
},
observer.OnError,
() =>
{
branch.Move(length);
if (separator == null)
{
currentCompleted();
}
else
{
subscription.SetDisposableIndirectly(() =>
separator.Parse(branch).SubscribeSafe(
separatorResult =>
{
hasSeparatorResult = true;
separatorLength = Math.Max(separatorLength, separatorResult.Length);
},
observer.OnError,
() =>
{
branch.Move(separatorLength);
currentCompleted();
}));
}
}));
});
if (nonGreedy && count == 0)
{
var startSubscription = new SingleAssignmentDisposable();
var lookAhead = new LookAheadParseResult <IObservable <TResult> >(Observable.Empty <TResult>(), length: 0);
var lookAheadSubscription = lookAhead.Subscribe(success =>
{
if (success)
{
onCompleted();
}
else
{
startSubscription.Disposable = start();
}
});
observer.OnNext(lookAhead);
return new CompositeDisposable(branch, subscription, lookAhead, lookAheadSubscription, startSubscription);
}
else
{
var startSubscription = start();
return new CompositeDisposable(branch, subscription, startSubscription);
}
}));
}