This is incredibly common in embedded programming. Lots of times you'll have some binary packet come over the wire, the first field is a packet type specifier,

This is incredibly common in embedded programming. Lots of times you'll have some binary packet come over the wire, the first field is a packet type specifier, you can then just cast the rest of your byte buffer to the proper type. It is very unfortunate that C (and until recently C++) did not have a way to specify the size of enums. Basically this has resulted in crappy #defines being used for far too many years. I always called what you did above "tagged types". A number of type systems actually work like that under the covers, objects get a type ID, and then a lookup function figures out what that type ID maps to.