> No, MRV being a language construct does not allow that at all (you can't do any such thing in Go because MRVs are language structures rather than properly rei

> No, MRV being a language construct does not allow that at all (you can't do any such thing in Go because MRVs are language structures rather than properly reified). Oops, I meant "because MRVs are a first-class language construct in CL (if only because of macros), you can abstract over them ..." Secondly, tagged unions are a very standard way of simulating sum types in languages that lack them. All I was saying is that MRVs can be used in a similar way. E.g., an option can be replaced by a pair of values, one of which indicates whether or not the value is present and the other indicates what the value was. As far as the boilerplate issue goes, if you really need to make sure that a field is present, you should be using hash tables in CL, you use a class and when you try to access an unbound slot, it throws. Finally, it's just wrong to say that Options are only useful in statically typed languages: any _strongly_ typed language can use them effectively, whether or not those types are checked at run time or compile time.