Ruby's Hash is a Swiss-Army Knife

When I used to program in C# (or even Java before that), one of the topics that always puzzled me was when to use which class. There are literally thousands and thousands of classes in the core language, framework, and the standard library. For example, here are the five types that implement the IDictionary interface in C#. HashtableSortedListSortedList<TKey, TValue>Dictionary<TKey, TValue>Concurr