Iterable can be thought of a designation that says "this class can be iterated over." So for example, HashSet is iterable, but HashSet itself is not an iterator. All that Iterable guarantees is that the class returns a concrete object that implements Iterator. Iterator is the concrete object that you actually use to iterate over the collection. The implementing class controls how to actually traverse the collection. do I just have to return a linked list of some sort (stack/queue)? why not use iterator instead? To reiterate the above, what you are returning is an object that implements Iterable. So yes, you could use a LinkedList or ArrayList because they implement Iterable. If you require more fine-tuned control over the iterator, then you could do something like this: public Iterable solution(){ return new Iterable(){ public Iterator iterator(){ //Return your iterator } } } You will need to create an inner class that implements Iterator and specifies how to actually iterate over all the boards. Look up how to properly implement Iterator, for example . More on reddit.com

I need to understand what is iterator and generators. I looked into YouTube and gone through documents but didn’t get it. What is the purpose, impact and where and when one can use it? Its quite confusing. Please help. More on discuss.python.org

An iterator is an object which has a __next__ method. An iterable is an object which has a __getitem__ method or has an __iter__ method. You iterate over things with an iterator. You can get an iterator from an iterable. The syntax for x in iterable calls iter(iterable) to get an iterator, then uses that iterator until StopIteration is thrown. Roughly equivalent to this: try: it = iter(iterable) while True: do_thing_with(next(it)) except StopIteration: pass Here's a repl.it with an example of each: https://repl.it/KNPC/0 More on reddit.com

Channels are almost perfect... except the performance is absolute trash for a lot of common iterator cases. Imagine the difference between a conventional for loop incrementing an index, which amortizes to about one processor cycle per loop, versus a channel. To get the next int, we must block the current goroutine, deschedule it, schedule the providing goroutine, have it generate the next value and put it on the channel, deschedule that goroutine, reschedule the consumer, and extract the value from the channel. There's no way to make that fast enough. If you do try to optimize it to remove the cross-goroutine communication, if you work through the process you largely end up with the current proposal. How that is may be subtle and require you to learn about how compilers optimize code internally by representing things as "coroutines" (that's your search engine term) and it's s number of steps, but it is where you end up to a great degree. It's a real pity, the semantics of the channel are pretty good. Edit: See u/assbuttbuttass ' post for resources that will do a lot of the walking through what I meant by "if you try to just optimize channels, you end up pretty close to this proposal anyhow". I was too lazy on my phone at the time to dig them up. Thanks assbuttbuttass. (And thanks for the opportunity to type that sentence.) You could still argue that "the compiler could just optimize down to this" but it's another one of the things that come up so frequently in language design where that seems like it works from the 30,000 foot view but on the ground it just isn't practical. Also, channels do work for cases where the process of generating the next thing and/or consuming the next thing is much, much more expensive than even the expense of all the scheduling. If it's 100ms to handle each things in the iteration, it doesn't matter if it's a microsecond or two to get the next thing so much. Unfortunately, wanting to iterate on int indexes or "the next thing in the hash table", which is pretty cheap on its own, is extremely common and the concurrency expense kills those. More on reddit.com