enumerator

What is the best way to convert a non-generic collection to a generic collection? Is there a way to LINQ it? I have the following code. public class NonGenericCollection:CollectionBase { public void Add(TestClass a) { List.Add(a); } } public class ConvertTest { public static List<TestClass> ConvertToGenericClass( NonGenericCollection collection) { // Ask for help here. } } Thanks! Mark Brackett Since you can guarantee they're all TestClass instances, use the LINQ Cast<T> method : public static List<TestClass> ConvertToGenericClass(NonGenericCollection collection) { return collection.Cast

Does anyone know if there was a specific reason or design decision to not include a reverse enumerator in C#? It would be so nice if there was an equivalent to the C++ reverse_iterator just like Enumerator is the equivalent of the C++ iterator . Collections that can be reverse-iterated would just implement something like IReverseEnumerable and one could do something like: List<int>.ReverseEnumerator ritr = collection.GetReverseEnumerator(); while(rtir.MoveNext()) { // do stuff } This way, you would be able to iterate Lists and LinkedLists in the same way rather than using indexer for one and

code: c = 0 items.each { |i| puts i.to_s # if c > 9 escape the each iteration early - and do not repeat c++ } I want to grab the first 10 items then leave the "each" loop. What do I replace the commented line with? is there a better approach? something more Ruby idiomatic? While the break solution works, I think a more functional approach really suits this problem. You want to take the first 10 elements and print them so try items.take(10).each { |i| puts i.to_s } Sarah Vessels There is no ++ operator in Ruby. It's also convention to use do and end for multi-line blocks. Modifying your

I was looking up the difference between the two classes and this point came up in a lot of the answers with this blog being the source: http://javarevisited.blogspot.com/2010/10/difference-between-hashmap-and.html However I don't completely get it. Can someone elaborate this? Perhaps with an example? Thanks for looking in! evanwong Fail-fast means when you try to modify the content when you are iterating thru it, it will fail and throw ConcurrentModificationException. Set keys = hashMap.keySet(); for (Object key : keys) { hashMap.put(someObject, someValue); //it will throw the

TLDR: Is there a thread-safe version of the Enumerator class in Ruby? What I'm trying to do: I have a method in a Ruby On Rails application that I wanted to run concurrently. The method is supposed to create a zip file containing reports from the site, where each file in the zip is a PDF. The conversion from html to PDF is somewhat slow, thus the desire to multi-thread. How I expected to do it: I wanted to use 5 threads, so I figured I would have a shared Enumerator between the threads. Each thread would pop a value from the Enumerator, and run do stuff to it. Here's how I was thinking it

If I create an Enumertor like so: enum = [1,2,3].each => #<Enumerator: [1, 2, 3]:each> enum is an Enumerator. What is the purpose of this object? I can't say this: enum { |i| puts i } But I can say this: enum.each { |i| puts i } That seems redundant, because the Enumerator was created with .each . It seems like it's storing some data regarding the each method. I don't understand what's going on here. I'm sure there is some logical reason we have this Enumerator class, but what can it do that an Array can't? I thought maybe it was an ancestor of Array and other Enumerables, but it doesn't seem