On Thu, Feb 10, 2022 at 10:39:26AM +0100, PICCA Frederic-Emmanuel wrote:
Then it seems to me that I just need to define a merge function like this
merge :: PrimMonad m => MCube (PrimState m) -> Frame -> m ()
and then an unsafeFreeze to avoid copy. It that correct?
Well, the `unsafeFreeze` would typicall only be appropriate in pure functions that *construct* a pure `Cube` from scratch by allocating and mutating an `MCube`. As for merge itself, it runs in IO and mutates an `MCube`. It is the caller's responsibility to ensure that that object is not "shared". If the entire computation runs in `IO` then you just use MCube(s) throughout. Once you have a pure `Cube`, you would typically not mutate it in place, except in "linear" use-cases that *consume* its *sole* reference while mutating it in place (possibly returning a fresh Cube based on the modified copy). Ensuring "linearity" is not trivial (a key reason for the existence of "Rust"). Use of `unsafeThaw` is atypical. -- Viktor.