You can improve performance if you unroll recurse to stack, so you will have only one iterator: public IEnumerable<Foo> GetAll() { Stack<Foo> FooStack = new Stack<Foo>(); FooStack.Push(this); while (FooStack.Count > 0) { Foo Result = FooStack.Pop(); yield return Result; foreach (Foo NextFoo in Result.MyChildren) FooStack.Push(NextFoo); } }
It specifies that an iterator has come to an end. You can think of yield break as a return statement which does not return a value. For example, if you define a function as an iterator, the body of the function may look like this: for (int i = 0; i < 5; i++) { … Read more
Seemingly, yield is syntactic sugar for wrapping what it returns to in a callback and assigning the result value appropriately (and at least in the case of co, throwing the error argument to the callback) No, yield is no syntactic sugar. It’s the core syntax element of generators. When that generator is instantiated, you can … Read more
yield works by building a state machine internally. It stores the current state of the routine when it exits and resumes from that state next time. You can use Reflector to see how it’s implemented by the compiler. yield break is used when you want to stop returning results. If you don’t have a yield … Read more
I suspect this is a matter of practicality rather than feasibility. I suspect there are very, very few times where this restriction is actually an issue that can’t be worked around – but the added complexity in the compiler would be very significant. There are a few things like this that I’ve already encountered: Attributes … Read more
Source: http://www.javamex.com/tutorials/threads/yield.shtml Windows In the Hotspot implementation, the way that Thread.yield() works has changed between Java 5 and Java 6. In Java 5, Thread.yield() calls the Windows API call Sleep(0). This has the special effect of clearing the current thread’s quantum and putting it to the end of the queue for its priority level. In … Read more
Late answering, probably everybody knows about yield now, but some better documentation has come along. Adapting an example from “Javascript’s Future: Generators” by James Long for the official Harmony standard: function * foo(x) { while (true) { x = x * 2; yield x; } } “When you call foo, you get back a Generator … Read more
You are reusing the same list object. Your generator returns the one object over and over again, manipulating it as it goes, but any other references to it see those same changes: >>> r = list(gen()) >>> r [[4], [4], [4], [4], [4]] >>> r[0] is r[1] True >>> r[0][0] = 42 >>> r [[42], … Read more
Yes, it’ still a generator. The return is (almost) equivalent to raising StopIteration. PEP 255 spells it out: Specification: Return A generator function can also contain return statements of the form: “return” Note that an expression_list is not allowed on return statements in the body of a generator (although, of course, they may appear in … Read more
If you don’t use the results of your yields,* you can always turn this: yield from foo … into this: for bar in foo: yield bar There might be a performance cost,** but there is never a semantic difference. Are the entries from the two halves (upper and lower) appended to each other in one … Read more