[swift-evolution] [Review] SE-0104: Protocol-oriented integers
plxswift at icloud.com
Fri Jun 24 20:16:51 CDT 2016
+1 but with a few reservations.
What *are* the expected semantics of the operators? It seems like you can’t assume much about a generic `Arithmetic` type, e.g. in a generic context I can’t reliably assume even things like these:
- `(x / y) * y == x` (or even “is close to" x)
- `(x + x + … + x) / n == x` (for `x` added together `n` times)
- `((x + y) + z) == (x + (y + z))` (etc.)
- `(x + y) - y == x`(? I think...)
…and so on; am I missing something?
If `Arithmetic` is as lacking in semantics as it seems, then it feels like one of those “bag of syntax” protocols that keep getting mentioned as against the stdlib philosophy.
# More Bit Operations
These don’t have to go into a v1, but I’d like to request seriously considering baking good support for things like popcount first set bit, etc., directly into the appropriate protocol (`FixedWidthInteger`?).
I won’t pretend there are specific generic algorithms simply waiting on their presence or anything…it just seems like a logical extension of the rationalized bit-shifting behavior in the proposal (and at least IMHO things like popcount really ought to have been fundamental operations on par with the shifts and bitwise operations, but that’s an aside).
# Endianness & Byte-Reversal
Endianness seems entirely unaddressed. I assume it’s intentional and, if so, I agree it’s *mostly* best omitted...but I’m curious if there’s already a plan for addressing that at this level or not? Even if just including a function like `func byteReversed() -> Self` (etc.) on a suitable protocol (e.g. `FixedWidthInteger`, or perhaps a new refinement thereof?).
I think that’s it for now. Overall I like it!
> On Jun 22, 2016, at 7:52 PM, Chris Lattner via swift-evolution <swift-evolution at swift.org> wrote:
> Hello Swift community,
> The review of "SE-0104: Protocol-oriented integers" begins now and runs through June 27. The proposal is available here:
> Reviews are an important part of the Swift evolution process. All reviews should be sent to the swift-evolution mailing list at
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