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by joe_the_user
3926 days ago
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Amazingly, there is no easy way to define a type in C++ which can be "one of these or one of these", e.g. a sphere or a group in this case. The author may have assumptions I'm missing here but the standard way to have a "one of these or one of these" thing is to have two classes inherent from a given abstract base class and use a pointer to the base class. If one wants the device specifically as a type, one could wrap the base-pointer in a class. Is there something I'm missing? |
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Some of the things that make me miss OCaml variants/sum types when I have to use C++ subclassing/dynamic dispatch instead: * very lightweight syntax both for creating them and matching on them (and lightweight representation; variants without arguments are just ints under the hood) * compile-time checks on exhaustiveness in pattern matches (so no unexpected NULL's!)
Note that OCaml also allows open/polymorphic variants for the cases where you want to allow expanding the list of options – here the compiler will only check that e.g. a function that matches on only `A|`B won't be sent a `C, although it can be sent a member of a type that contains only `A's. This is typically used for public interfaces where you want to let your implementation expand later (e.g. your current function accepts `UTF8|`UTF16 but you might later decide to accept `WTF8 as well).