4 ms·

This isn't true in general, it's only true when T is a pointer type, in which case C++ would just use a pointer.

• pcwalton 11y ago
  Or if T is NonZero. More importantly, dereferencing a None is not undefined behavior in Rust.
  • detrino 11y ago
    > Or if T is NonZero. Ok, I wasn't aware of this. >More importantly, dereferencing a None is not undefined behavior in Rust. That's an unrelated point. I never said Rust enum's have no advantages.
  • Gankro 11y ago
    Or if T contains a NonZero (Vec, VecDeque, HashMap) ;)
• vvanders 11y ago
  It seems like that wasn't the case for the proposed C++ variant. It seems like you would have to use some sort of sentinel value to discriminate between None and Some(or virtual which is even worse). Rust explicitly omits the sentinel value and leaves it to the compiler so that it can decide how to optimize best.
  • detrino 11y ago
    I'm just saying you wouldn't use std::variant<T star>, you'd just use T star. Also C++ has the meta-programming capabilities to special variant for pointers. edit: replaced * with star to defeat italicizer.
    • whyever 11y ago
      And then you have to deal with null pointers.
      • detrino 11y ago
        This is an unrelated point, we were talking about representation.
    • deleted 11y ago
      [deleted]