On Wed Feb 19, 2025 at 5:51 AM JST, Timur Tabi wrote:
> On Tue, 2025-02-18 at 22:16 +0900, Alexandre Courbot wrote:
>> > A proper struct with `high` and `low` might be more verbose, but
>> > it rules out this issue.
>>
>> Mmm indeed, so we would have client code looking like:
>>
>> let SplitU64 { high, low } = some_u64.into_u32();
>>
>> instead of
>>
>> let (high, low) = some_u64.into_u32();
>>
>> which is correct, and
>>
>> let (low, high) = some_u64.into_u32();
>>
>> which is incorrect, but is likely to not be caught.
>
> I'm new to Rust, so let me see if I get this right.
>
> struct SplitU64 {
> high: u32,
> low: u32
> }
>
> So if you want to extract the upper 32 bits of a u64, you have to do this:
>
> let split = some_u64.into_u32s();
> let some_u32 = split.high;
More likely this would be something like:
let SplitU64 { high: some_u32, .. } = some_u64;
Which is still a bit verbose, but a single-liner.
Actually. How about adding methods to this trait that return either
component?
let some_u32 = some_u64.high_half();
let another_u32 = some_u64.low_half();
These should be used most of the times, and using destructuring/tuple
would only be useful for a few select cases.
>
> as opposed to your original design:
>
> let (some_u32, _) = some_u64.into_u32s();
>
> Personally, I prefer the latter. The other advantage is that into_u32s and
> from_u32s are reciprocal:
>
> assert_eq!(u64::from_u32s(u64::into_u32s(some_u64)), some_u64);
>
> (or something like that)
Yeah, having symmetry is definitely nice. OTOH there are no safeguards
against mixing up the order and the high and low components, so a
compromise will have to be made one way or the other. But if we also add
the methods I proposed above, that question should matter less.
