3 ms·

This is what people mean when they say "make invalid states unrepresentable", languages with union types can easily avoid this problem.

• biorach 1y ago
  It doesn't sound like they are talking about invalid states, more like they are taking about the kind of thing that in Rust would be represented by `Option<Box<dyn SomeTrait>>` or suchlike. Maybe your point is that in Rust much less ceremony is necessary to avoid hitting a null pointer when doing this. But still, in either language it's easy to end up with hard to follow logic when doing this.
  • DanielHB 1y ago
    not super familiar with Rust but isn't Option<T> just an union type of null and T? I get the language has special semantics for this compared to a union type but it is conceptionally just an union. For example this is something you can do with typescript. function(args: Arguments) { ... } type Arguments = { a: number, b: number } | { a: number, b: string, c: number } the Arguments { a: 1, b: 1, c: 1 } is not representable.
    • qzzi 1y ago
      I'm pretty sure they're talking about reference counting that depends on the arguments, not about optional arguments or invalid argument combinations.
    • 0x457 1y ago
      > not super familiar with Rust but isn't Option<T> just an union type of null and T? Only if there is a niche optimization happens if T is never null, otherwise it's a tagged union. That's not what you're replying to is about.