public static IEnumerableAsync <Tuple <T1, T2> > Zip <T1, T2>(this IEnumerableAsync <T1> input1, IEnumerableAsync <T2> input2)
{
return(Produce <Tuple <T1, T2> >(async yieldAsync =>
{
IEnumeratorAsync <T1> enum1 = NullEnumerator <T1> .Instance;
IEnumeratorAsync <T2> enum2 = NullEnumerator <T2> .Instance;
await TryFinallyAsync(
async() =>
{
enum1 = await input1.GetEnumerator();
enum2 = await input2.GetEnumerator();
while (AllTrue(await Task.WhenAll(enum1.MoveNext(), enum2.MoveNext())))
{
await yieldAsync.YieldAsync(Tuple.Create(enum1.Current, enum2.Current));
}
return 0;
},
() => Task.WhenAll(enum1.Dispose(), enum2.Dispose())
);
}));
}
async Task <bool> EnumeratorMoved()
{
await open.Task;
bool result;
var enumeratorMovedRef = enumeratorMoved;
if (Interlocked.Decrement(ref awaitedEnumerators) == 0)
{
result = await enumerator.MoveNext();
awaitedEnumerators = totalEnumerators;
enumeratorMoved = new TaskCompletionSource <bool>();
enumeratorMovedRef.SetResult(result);
}
else
{
result = await enumeratorMovedRef.Task;
}
await Task.Yield();
return(result);
}