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

Fri Jul 1 02:17:02 CDT 2016

Bah, of course. No point in trying to qualify the word; let's just call it
the memory layout stride and be done with it.

On Fri, Jul 1, 2016 at 02:05 Dave Abrahams <dabrahams at apple.com> wrote:

> No, actually both can be something other than the minimum.  These are
> usually going to be the minimum-without-performance-degradation.
>
>
> Sent from my illudium Q-36 explosive space modulator
>
> On Jun 30, 2016, at 11:29 PM, Xiaodi Wu <xiaodi.wu at gmail.com> wrote:
>
> 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
>>> <http://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> <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
>>> <http://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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>>
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