public static IEnumerableAsync <TSelect> SelectOptional <TItem, TSelect>(this IEnumerableAsync <TItem> enumerable,
Func <TItem, Func <TSelect, ISelectionResult <TSelect> >, Func <ISelectionResult <TSelect> >, ISelectionResult <TSelect> > selection)
{
return(enumerable.SelectOptional <TItem, TSelect, int, IEnumerableAsync <TSelect> >(1,
(item, carryUpdated, next, skip) => selection(item,
(selected) => next(selected, 1),
() => skip(1)),
(aggregation, carryUpdated) => aggregation));
}
public static TResult SelectOptionalIndexed <TItem, TSelect, TCarry, TResult>(this IEnumerableAsync <TItem> enumerable,
TCarry carry,
Func <TItem, TCarry, int, Func <TSelect, TCarry, ISelectionResult <TSelect> >, Func <TCarry, ISelectionResult <TSelect> >, ISelectionResult <TSelect> > selection,
Func <IEnumerableAsync <TSelect>, TCarry, TResult> aggregation)
{
int index = 0;
return(enumerable.SelectOptional(carry,
(item, carryUpdated, next, skip) => selection(item, carryUpdated, index++, next, skip),
aggregation));
}
public static TResult SelectOptional <TItem, TSelect, TCarry1, TCarry2, TResult>(this IEnumerableAsync <TItem> enumerable,
TCarry1 carry1, TCarry2 carry2,
Func <TItem, TCarry1, TCarry2,
Func <TSelect, TCarry1, TCarry2, ISelectionResult <TSelect> >,
Func <TCarry1, TCarry2, ISelectionResult <TSelect> >,
ISelectionResult <TSelect> > selection,
Func <IEnumerableAsync <TSelect>, TCarry1, TCarry2, TResult> aggregation)
{
return(enumerable.SelectOptional(carry1.PairWithValue(carry2),
(item, carryUpdated, next, skip) => selection(item, carryUpdated.Key, carryUpdated.Value,
(selected, carry1Updated, carry2Updated) => next(selected, carry1Updated.PairWithValue(carry2Updated)),
(carry1Updated, carry2Updated) => skip(carry1Updated.PairWithValue(carry2Updated))),
(IEnumerableAsync <TSelect> selectedItems, KeyValuePair <TCarry1, TCarry2> carryFinal) =>
aggregation(selectedItems, carryFinal.Key, carryFinal.Value)));
}
