3 ms·

A question to the Rust experts, would lifetime annotations 'a in Rust have similar benefit as "in" or "in out" or "out" in Ada and other languages? With the add

• chc 4y ago
  As a sibling comment points out, "in" is effectively equivalent to "&T", and "inout" is effectively equivalent to "&mut T". Rust is missing purely "out" parameters, but that isn't a very common case, and I'm not sure how much value there is in saying "this reference can't be read" since references are always guaranteed to be valid in Rust.
  • db48x 4y ago
    A Rust program can trivially return a tuple of values, so it doesn't need out params.
    • zozbot234 4y ago
      Out params are needed to ensure zero-copy in-place initialization of large objects, i.e. what C++ does with placement new. You can sort of fake it with MaybeUninit<> https://doc.rust-lang.org/std/mem/union.MaybeUninit.html https://doc.rust-lang.org/std/mem/union.MaybeUninit.html but it's quite fiddly, requires unsafe code, and has undesirable effects on the layout of containing objects.
      • db48x 4y ago
        In–place initialization is nice to have, but not strictly required.