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by orthoxerox9 hours ago |
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upvoteby SideburnsOfDoom9 hours ago|
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It's very unclear which you mean by that.

To me that "compiler-verified" maps to "sealed", not "on the fly". Probably.

Their example is:

public union Pet(Cat, Dog, Bird);

Pet pet = new Cat("Whiskers");

- the union type is declared upfront, as is usually the case in c#. And the types that it contains are a fixed set in that declaration. Meaning "sealed" ?

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upvoteby pjc509 hours ago|
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OK then, what is the opposite of this, the adhoc union?
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upvoteby Semaphor9 hours ago|
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I don’t know for sure, but I’m guessing something like

(Dog, Cat) pet = new Cat();

So without defining the union with an explicit name beforehand.

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upvoteby SideburnsOfDoom8 hours ago|
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Well, you can do this in c#:

  var someUser = new { Name = "SideburnsOfDoom", CommentValue = 3 };
What type is `someUser` ? Not one that you can reference by name in code, it is "anonymous" in that regard. But the compiler knows the type.

A type can be given at compile-time in a declaration, or generated at compile-time by the compiler like this. But it is still "Compiler-verified" and not ad-hoc or at runtime.

the type (Dog, Cat) pet seems similar, it's known at compile-time and won't change. A type without a usable name is still a type.

Is this "ad-hoc"? It depends entirely on what you mean by that.

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upvoteby SideburnsOfDoom9 hours ago|
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I don't follow the question. Maybe define the term that you are using?
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upvoteby pjc509 hours ago|
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Top comment mentioned the term without defining it, confusing me and seemingly most of the thread: https://news.ycombinator.com/item?id=47649817
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upvoteby orthoxerox5 hours ago|
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I mean that Cat, Dog and Bird don't have to inherit from the union, you can declare a union of completely random types, as opposed to saying "Animal has three subtypes, no more, no less", which is what F# does more or less.
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