yield

So i found this keyword that i did not know about in c#. Intriguing. So what it does is creates an enumeration on the fly, without having to code a class to do it. Sounds good, but what could i use it in. A few examples suggest that it be used in tree traveral:

        public IEnumerator<Node> GetDepthFirstTraversalEnumerator() {

            yield return this.value;

            foreach(Node child in this.children) {

                IEnumerator<Node> enum_ = kidchildGetDepthFirstTraversalEnumerator();

                while(enum_.MoveNext()) {

                    yield return enum_.Current;

                }

            }

        }

and also found the map function from other laungauges:

        public delegate object MapFunction(object o);

        public static IEnumerable Map(MapFunction mapFunction, IEnumerable enumerable) {

            foreach(object o in enumerable) {

                yield return mapFunction(o);

            }

        }

        public static IEnumerable PositiveIntegers() {

            int a = 1;

            while(true) {

                yield return a;

                a = a + 1;

            }

        }

        public static IEnumerable SubList(int start, int end, IEnumerable enumerable) {

            int count = 0;

            foreach(object o in enumerable) {

                count++;

                if(count < start) {

                    continue;

                } else if(count <= end) {

                    yield return o;

                } else {

                    yield break;

                }

            }

        }

        IEnumerable set = I.SubList(5, 15, I.PositiveNumbers());

        foreach(int value in Map(delegate(object o) { return ((int)o) * 2; }, )) {

            //do something

        }

heres the link to a Fibonacci generator 

http://www.cerkit.com/cerkitBlog/2004/06/30/Using+The+Yield++Statement+In+Whidbey+C.aspx

a lazy paged collection:

http://haacked.com/archive/2006/08/14/FunIteratingPagedCollectionsWithGenericsAndIterators.aspx

and a textreader:

http://blogs.msdn.com/jmstall/archive/2005/08/08/textreader_yield.aspx