On Mon, Dec 21, 2020 at 7:30 PM Robby Findler <ro...@cs.northwestern.edu>
wrote:
> Is Typed Racket able to prove that your use of unsafe accessors is
> actually safe?
>
On a similar note, my understanding is that, even without types, in a
program like this:
#lang racket
(struct cell (val))
(λ (x)
(if (cell? x)
(cell-val x)
...))
the compiler can optimize the use of `cell-val` guarded by `cell?` to omit
the redundant check. I think the optimized version should be as good as
`unsafe-struct-ref`.
If that's the case, the only extra invariant for `unsafe-struct*-ref` is
that it does not work on impersonators (including chaperones, IIUC). If you
need the extra performance, I think you can get it safely by declaring your
structs as `#:authentic` (or equivalently adding `prop:authentic`), which
will cause the struct types involved not to support impersonators:
`impersonate-struct` and similar functions will raise exceptions. On the
other hand, if you need to support impersonators, then it really is unsafe
to use `unsafe-struct*-ref`.
-Philip
--
You received this message because you are subscribed to the Google Groups
"Racket Users" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to racket-users+unsubscr...@googlegroups.com.
To view this discussion on the web visit
https://groups.google.com/d/msgid/racket-users/010001768888c2ba-c84b6b21-d30d-488f-b4ad-43878e96f06d-000000%40email.amazonses.com.
