public static IAsyncIterator <T> WhereAsync <T>(this IAsyncIterator <T> iterator, Func <T, Task <bool> > predicate)
{
return(AsyncIterator.Create <IAsyncIterator <T>, T>(
iterator,
async(currentIterator) =>
{
while (true)
{
var result = await currentIterator.NextAsync();
if (result.HasValue)
{
var pair = result.ValueOrFailure();
var item = pair.Item1;
var nextIterator = pair.Item2;
if (await predicate(item))
{
return Tuple.Create(item, nextIterator).Some();
}
}
else
{
return Option.None <Tuple <T, IAsyncIterator <T> > >();
}
}
}
));
}
public static IAsyncIterator <S> SelectAsync <T, S>(this IAsyncIterator <T> iterator, Func <T, Task <S> > mapper)
{
return(AsyncIterator.Create <IAsyncIterator <T>, S>(
iterator,
async(currentIterator) =>
{
var result = await currentIterator.NextAsync();
if (result.HasValue)
{
var pair = result.ValueOrFailure();
var item = pair.Item1;
var nextIterator = pair.Item2;
return Tuple.Create(await mapper(item), nextIterator).Some();
}
else
{
return Option.None <Tuple <S, IAsyncIterator <T> > >();
}
}
));
}
public AsyncLATokenIterator(IAsyncIterator <Item> inputSource)
{
_inputSource = inputSource;
}
public static IAsyncIterator <T> Where <T>(this IAsyncIterator <T> iterator, Func <T, bool> predicate)
{
return(WhereAsync <T>(iterator, item => Task.FromResult(predicate(item))));
}
public static IAsyncIterator <S> Select <T, S>(this IAsyncIterator <T> iterator, Func <T, S> mapper)
{
return(iterator.SelectAsync(item => Task.FromResult(mapper(item))));
}
