Repeat the previous exercise, but using a variant record (union) type to represent syntax tree nodes. Repeat again using type extensions. Compare the three solutions in terms of clarity, abstraction,...

Repeat the previous exercise, but using a variant record (union) type to represent syntax tree nodes. Repeat again using type extensions. Compare the three solutions in terms of clarity, abstraction, type safety, and extensibility. Using the C# indexer mechanism, create a hash table class that can be indexed like an array. (In effect, create a simple version of the System .Collections.Hashtable container class.) Alternatively, use an overloaded version of operator[] to build a similar class in C++.