We do not use unions very often in C/C++ because they are not safe. You have to know how to interpret it; the compiler can't and won't save you if you read the

We do not use unions very often in C/C++ because they are not safe. You have to know how to interpret it; the compiler can't and won't save you if you read the memory as the wrong type. You usually keep a variable set to the type the union is, and check it at run time. Some languages do that wrapping and checking for you, automatically. Everything from Ada (variant records) to Haskell has them. You cannot mishandle such objects by misinterpreting them as the wrong type; it's a compile-time error in those languages to do so. Imagine you are parsing something. In my opinion, the most natural way to express this, is a function that takes an array of characters and returns an array of parsed objects or tokens, where each object may be of a different possible type. In C, you'd probably use a union of structs, and set which type of struct as you parse each object. This is error prone and verbose, and the compiler can't double-check it for you. It's all automatic in a language with sum types. Quite efficiently too; most of the runtime checks can be optimized away.