[swift-evolution] [Review] SE-0101: Rename sizeof and related functions to comply with API Guidelines

Fri Jul 1 01:29:48 CDT 2016

I don't think it needs qualifying. It cannot be anything other than the
minimum, just like we have `alignment` instead of `minimumAlignment`.
On Fri, Jul 1, 2016 at 00:50 Jacob Bandes-Storch via swift-evolution <
swift-evolution at swift.org> wrote:

> There seems to be agreement that "stride" is sensical term for the
> distance between values in memory, but it seems like what MemoryLayout
> wants to expose is the *minimum* possible stride for a particular type. How
> do folks feel about "*minimumStride*"?
>
> On Thu, Jun 30, 2016 at 10:46 PM, James Berry via swift-evolution <
> swift-evolution at swift.org> wrote:
>
>>
>> > On Jun 30, 2016, at 10:07 PM, Dave Abrahams <dabrahams at apple.com>
>> wrote:
>> >
>> >
>> > on Thu Jun 30 2016, Matthew Johnson <matthew-AT-anandabits.com> wrote:
>> >
>> >>> On Jun 30, 2016, at 8:12 PM, Dave Abrahams <dabrahams at apple.com>
>> wrote:
>> >>>
>> >>>
>> >>> on Thu Jun 30 2016, Matthew Johnson <matthew-AT-anandabits.com <
>> http://matthew-at-anandabits.com/>> wrote:
>> >>>
>> >>
>> >>>> Sent from my iPad
>> >>>>
>> >>>>> On Jun 30, 2016, at 6:59 PM, Erica Sadun via swift-evolution <
>> swift-evolution at swift.org> wrote:
>> >>>>>
>> >>>>>
>> >>>>>>> On Jun 30, 2016, at 5:47 PM, James Berry <jberry at rogueorbit.com>
>> wrote:
>> >>>>>>>
>> >>>>>>>
>> >>>>>>> On Jun 30, 2016, at 4:05 PM, Dave Abrahams via swift-evolution <
>> swift-evolution at swift.org> wrote:
>> >>>>>>> on Thu Jun 30 2016, Erica Sadun <erica-AT-ericasadun.com> wrote:
>> >>>>>>>
>> >>>>>>>>> On Jun 30, 2016, at 4:41 PM, Dave Abrahams <dabrahams at apple.com>
>> wrote:
>> >>>>>>>>>> I mentioned this in a comment on the gist already, but I'm
>> really not
>> >>>>>>>>>> digging the "array" in `arraySpacing`. We've already moved
>> from top-level
>> >>>>>>>>>> "stride" to "memory layout spacing," gaining plenty of
>> clarity. I'm
>> >>>>>>>>>> skeptical that the "array" adds anything more. Moreover, it
>> muddies the
>> >>>>>>>>>> waters by mentioning a specific type (Array) in a context
>> where you're
>> >>>>>>>>>> querying the memory layout properties of another type.
>> >>>>>>>>>
>> >>>>>>>>> OK, I agree with that.  If we have “alignment” rather than
>> >>>>>>>>> “defaultAlignment,” I suppose we can have plain “spacing.”
>> >>>>>>>>
>> >>>>>>>> No way to last-second sell you on interval rather than spacing?
>> >>>>>>>
>> >>>>>>> If you can explain why it's better.
>> >>>>>>>
>> >>>>>>>> // Returns the least possible interval between distinct
>> instances of
>> >>>>>>>> /// `T` in memory.  The result is always positive.
>> >>>>>>>
>> >>>>>>> For me, “interval” doesn't go with “size” and “alignment,” which
>> are all
>> >>>>>>> about physical distances and locations.  There are all kinds of
>> >>>>>>> “intervals,” e.g. time intervals.
>> >>>>>>
>> >>>>>> Hmm. Sounds like stride to me. stride or byteStride?
>> >>>>>>
>> >>>>>> James
>> >>>>>
>> >>>>> FAQ: "Why aren't you using the obvious phrase `stride` for
>> something that clearly
>> >>>>> returns the memory stride?"
>> >>>>>
>> >>>>> ANSWER: "As stride already has a well-established meaning in the
>> standard library,
>> >>>>> this proposal changes the name to spacing, providing a simple but
>> correct name that
>> >>>>> works well enough in its intended use. Measuring memory is
>> sufficiently esoteric
>> >>>>> that we prefer to reserve `stride` for a more common use case."
>> >>>>
>> >>>> Counter: some words have more than one well established meaning when
>> >>>> used in different contexts.  'spacing' isn't too bad here (much
>> better
>> >>>> than 'arraySpacing') but sticking to the term of art 'stride' would
>> be
>> >>>> best IMO.  As James mentioned, spacing implies empty space *between*
>> >>>> items whereas stride matches the meaning of this property *exactly*
>> >>>> (which is why it is the term of art).
>> >>>>
>> >>>> If a programmer can't distinguish between a 'stride' property on
>> >>>> MemoryLayout and the 'stride' function they probably have no business
>> >>>> doing anything which requires use of MemoryLayout in the first place.
>> >>>
>> >>> I don't believe that “stride” *is* the accepted term of art for this
>> >>> meaning.  I never heard of the idea of types having an intrinsic
>> >>> “stride” until I arrived on the Swift project.  That usage came from
>> >>> “strideof.”
>> >>>
>> >>> If you all swear up and down that you've been talking about “the
>> stride
>> >>> of a type” for more than 2 years, I won't fight you on this.
>> >>> Otherwise... well, I still won't fight; I'm being crushed by an
>> >>> avalanche of bikesheds and I can't muster the energy ;->... but I'll
>> >>> forever be plagued by doubts about the name.
>> >>
>> >> I was just throwing in my 2 cents and planned to leave it at that.
>> >> The primary reason I chimed in is because I didn’t find the rationale
>> >> in the “answer” compelling.  This isn’t something I feel like bike
>> >> shedding any further over either.
>> >>
>> >> https://en.wikipedia.org/wiki/Stride_of_an_array
>> >>
>> >> Maybe stride isn’t as common as I thought it was (if it was I’m sure
>> >> you would have heard of it before Swift) but it certainly predates
>> >> Swift in usage.
>> >
>> > But that's actually a different meaning altogether.  Two “arrays” of
>> > type T can have different strides.  They're talking about taking a view
>> > onto an underlying series of contiguous Ts that (potentially) skips over
>> > elements.
>>
>> Maybe I come from an esoteric part of the universe. While I’ve never
>> heard of stride applied to a type, in particular, the concept of stride as
>> I know it applies to any item as laid out in memory, and seems to me to
>> apply equally well to any “object” in the loosest form of the word. I
>> believe my first experience with it, some 30 years ago, dealt with the row
>> stride in a frame buffer or bitmap. This meaning is similar to the array
>> reference as above. I disagree that they’re not in that article above
>> talking primarily about the same thing that we are: their very first
>> example, under the “Padding” headline, seems to exactly match our intent.
>> Their additional examples are just hacks/extensions of this concept.
>>
>> If we were talking about waveforms we’d be talking about period. Stride
>> indicates the same thing with regard to items in memory: how long a step do
>> you need to take to get from the start of one item to the start of the
>> next. So we could use “period”, or “interval”, or “step”, or something. I’m
>> just arguing that the most recognizable word to describe this concept, as
>> applied to any sort of item in memory, is stride. But again, maybe that’s
>> just based on my own experience.
>>
>> Ultimately, I’m sure it’s not a big deal. I agree with Mathew that people
>> using MemoryLayout aren’t likely to confuse the two uses within swift. It’s
>> just that if I had to describe the concept we’re describing in
>> MemoryLayout, stride would be my first choice, as it seems most apt. Short
>> of that, I’m sure that I could read comments and ultimately figure out that
>> “interval,” or “spacing,” or whatever, really means “stride” ;)
>>
>> James
>>
>>
>>
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