6 ms·

Problem is avoiding having to do Vec<Option<T>>

• Animats 9y ago
  If T is a reference type, doesn't Rust do an optimization where <Option<T>>> is implemented by using null pointers?
  • kevincox 9y ago
    Yes. This optimization is expected to be expanded in the future but there are currently "NonZero" types. Rust notices this and uses the zero value as the enum descriminant. So in this case the code generated is idential to a nullable pointer.
  • sanxiyn 9y ago
    Yes, but that doesn't help when T is not a reference type.
    • Animats 9y ago
      If it's not a reference type, then the Option enum value is probably small relative to the rest of the data in the type.
      • __s 9y ago
        Option<i32> is 8 bytes