public static IAsyncEnumerable <TValue> Empty <TValue>()
{
return(Create(() => Create <TValue>(
ct => TaskExt.Return(false, ct),
() => { throw new InvalidOperationException(); },
() => { })
));
}
public Task <bool> MoveNext(CancellationToken cancellationToken)
{
if (_disposed)
{
return(TaskExt.Return(false, CancellationToken.None));
}
return(_moveNext(cancellationToken));
}
public static IAsyncEnumerable <TResult> Repeat <TResult>(TResult element)
{
return(Create(() =>
{
return Create(
ct => TaskExt.Return(true, ct),
() => element,
() => { }
);
}));
}
public static IAsyncEnumerable <TResult> Generate <TState, TResult>(TState initialState, Func <TState, bool> condition, Func <TState, TState> iterate, Func <TState, TResult> resultSelector)
{
if (condition == null)
{
throw new ArgumentNullException("condition");
}
if (iterate == null)
{
throw new ArgumentNullException("iterate");
}
if (resultSelector == null)
{
throw new ArgumentNullException("resultSelector");
}
return(Create(() =>
{
var i = initialState;
var started = false;
var current = default(TResult);
return Create(
ct =>
{
var b = false;
try
{
if (started)
{
i = iterate(i);
}
b = condition(i);
if (b)
{
current = resultSelector(i);
}
}
catch (Exception ex)
{
return TaskExt.Throw <bool>(ex, ct);
}
if (!b)
{
return TaskExt.Return(false, ct);
}
if (!started)
{
started = true;
}
return TaskExt.Return(true, ct);
},
() => current,
() => { }
);
}));
}
