//public static ISequence<Option<TResult>> SelectMany<TSource, TCollection, TResult>
// (this ISequence<Option<TSource>> source,
// Func<TSource, ISequence<TCollection>> collectionSelector,
// Func<TSource, TCollection, TResult> resultSelector)
//{
// return
// source.SelectMany(option => option.HasValue ? collectionSelector(option.Value).Select(t => new Option<TCollection>(t)) : Nothing<TCollection>(),
// (option, cItem) =>
// option.HasValue && cItem.HasValue
// ? new Option<TResult>(resultSelector(option.Value, cItem.Value))
// : new Option<TResult>());
//}
public static ISequence <IOption <TResult> > SelectMany <TSource, TCollection, TResult>
(this ISequence <IOption <TSource> > source,
Func <TSource, ISequence <IOption <TCollection> > > collectionSelector,
Func <TSource, TCollection, TResult> resultSelector)
{
return(new FunctionalSequence <IOption <TResult> >(() =>
{
long g = 0;
return () =>
{
var pair = NtoN2Mapping.GetPair(g++);
var t = source.At(pair.I);
if (t.HasValue)
{
var cs = collectionSelector(t.Value);
var c = cs.At(pair.J);
return c.HasValue ? FromValue(resultSelector(t.Value, c.Value)) : Empty <TResult>();
}
else
{
return Empty <TResult>();
}
};
}));
}
