The two options I know of is Aviad Ben Dov’s infomancers-collections library from 2007 and Jim Blackler’s YieldAdapter library from 2008 (which is also mentioned in the other answer). Both will allow you to write code with yield return-like construct in Java, so both will satisfy your request. The notable differences between the two are: … Read more
To understand what yield does, you must understand what generators are. And before you can understand generators, you must understand iterables. Iterables When you create a list, you can read its items one by one. Reading its items one by one is called iteration: >>> mylist = [1, 2, 3] >>> for i in mylist: … Read more
A method using yield return must be declared as returning one of the following two interfaces: IEnumerable<SomethingAppropriate> IEnumerator<SomethingApropriate> (thanks Jon and Marc for pointing out IEnumerator) Example: public IEnumerable<AClass> YourMethod() { foreach (XElement header in headersXml.Root.Elements()) { yield return (ParseHeader(header)); } } yield is a lazy producer of data, only producing another item after the … Read more
Upd: Starting with Python 3.6 we have asynchronous generators and able to use yield directly inside coroutines. import asyncio async def async_generator(): for i in range(3): await asyncio.sleep(1) yield i*i async def main(): async for i in async_generator(): print(i) loop = asyncio.get_event_loop() try: loop.run_until_complete(main()) finally: loop.run_until_complete(loop.shutdown_asyncgens()) # see: https://docs.python.org/3/library/asyncio-eventloop.html#asyncio.loop.shutdown_asyncgens loop.close() Old answer for Python 3.5: … Read more
Before we introduce continuations we need to build some infrastructure. Below is a trampoline that operates on Iteration objects. An iteration is a computation that can either Yield a new value or it can be Done. sealed trait Iteration[+R] case class Yield[+R](result: R, next: () => Iteration[R]) extends Iteration[R] case object Done extends Iteration[Nothing] def … Read more
What are the cases where use of yield will be limiting, unnecessary, get me into trouble, or otherwise should be avoided? It’s a good idea to think carefully about your use of “yield return” when dealing with recursively defined structures. For example, I often see this: public static IEnumerable<T> PreorderTraversal<T>(Tree<T> root) { if (root == … Read more
We talked about this in the TC39 face-to-face meetings and it is deliberate that we don’t expose a way to detect whether a function is a generator or not. The reason is that any function can return an iterable object so it does not matter if it is a function or a generator function. var … Read more
It is something that F# supports with yield! for a whole collection vs yield for a single item. (That can be very useful in terms of tail recursion…) Unfortunately it’s not supported in C#. However, if you have several methods each returning an IEnumerable<ErrorInfo>, you can use Enumerable.Concat to make your code simpler: private static … Read more
Yes, you can do this: def infinity(start): yield start for x in infinity(start + 1): yield x This will error out once the maximum recursion depth is reached, though. Starting from Python 3.3, you’ll be able to use def infinity(start): yield start yield from infinity(start + 1) If you just call your generator function recursively … Read more
Generators exist in C++, just under another name: Input Iterators. For example, reading from std::cin is similar to having a generator of char. You simply need to understand what a generator does: there is a blob of data: the local variables define a state there is an init method there is a “next” method there … Read more