Oops thanks for being patient. By "this" I meant "dispatch on abstract
units/dimensions". The motivation is to be able to write a function which
takes a length without caring what the specific unit of that length is. Be
it feet or cm etc. This is to make the intent of the function clearer and
enable polymorphism. For example:
direction = 0radians
move(r::Angle) = direction += r
move(l::Length) = translate(direction, l)
Also speed could be defined as Ratio{d<:size, t<:time}. Which would be hard
to do using unitful as is
On Thu, 18 Feb 2016 at 10:25 AM Jeffrey Sarnoff <[email protected]>
wrote:
> Jake,
>
> It would be helpful to know more clearly what is the "this" that you are
> experimenting with "ways to achieve this"?
> I took a glance at your code, and one thing that is happening is you have
> left some low-hanging abstraction on the table. That constrains Julia's
> ability to simplify through organized multidispatch. I will give it more
> than a glance overnight -- pretend it all works perfectly, show me what you
> want to do with it then.
>
>
> On Wednesday, February 17, 2016 at 3:59:15 PM UTC-5, Jake Rosoman wrote:
>
>> Oh yup I thought that was the case but wanted to check.
>>
>> I've started experimenting with ways to achieve this but I am getting
>> massive amounts of code generated compared to Unitful. I just uploaded
>> uploaded my work so far at https://GitHub.com/jkroso/units.jl. If anyone
>> could help explain the difference in code gen that would be great and I'll
>> try contribute back to Unitful
>>
> On Thu, 18 Feb 2016 at 7:02 AM Andrew Keller <[email protected]>
>> wrote:
>>
>>> Hi Jake,
>>>
>>> I agree with Jeffrey's response mostly, but want to clarify that Unitful
>>> is not strictly focused on the SI system. You'll see that you can use units
>>> of acre-feet, very much not an SI unit, which could be useful if you happen
>>> to manage a water reservoir in the United States, I guess.
>>>
>>> If you were instead asking whether or not you could write methods that
>>> dispatch on the dimensions of a unit, the current answer is no, although
>>> maybe that could change eventually.
>>>
>>> Best,
>>> Andrew
>>>
>>> On Wednesday, February 17, 2016 at 3:25:37 AM UTC-8, Jeffrey Sarnoff
>>> wrote:
>>>>
>>>> Jake,
>>>>
>>>> Julia's type system is well suited to do just that. Unitful is focused
>>>> on units in SI system, things like Meters, Kilograms and Joules.
>>>>
>>>> One approach to abstract units like size, where size may be relative to
>>>> the number of pixels on a screen or the width of a page,
>>>> is define your own type, a kind of size relative to something. In your
>>>> example, s is not a unit of measure (strictly speaking);
>>>> s is a quantity interpreted in terms of some absolute or relative unit
>>>> of measure -- 5 pixels, 1/4 page. Because pixels and pages
>>>> are not always the same number of, say, millimeters, using SI units for
>>>> that abstraction likely is not what you want.
>>>>
>>>> If you want more guidance, please give some more context.
>>>>
>>>> On Wednesday, February 17, 2016 at 4:43:13 AM UTC-5, Jake Rosoman wrote:
>>>>>
>>>>> Is it possible to talk about abstract types of units like size. e.g
>>>>> `drawline(s::Size) = ...`?
>>>>>
>>>>> On Saturday, February 13, 2016 at 9:23:22 AM UTC+13, Andrew Keller
>>>>> wrote:
>>>>>>
>>>>>> I'm happy to share a package I wrote for using physical units in
>>>>>> Julia, Unitful.jl <https://www.github.com/ajkeller34/Unitful.jl>.
>>>>>> Much credit and gratitude is due to Keno Fischer for the SIUnits.jl
>>>>>> <https://www.github.com/keno/SIUnits.jl> package which served as my
>>>>>> inspiration. This is a work in progress, but I think perhaps a
>>>>>> serviceable
>>>>>> one depending on what you're doing.
>>>>>>
>>>>>> Like SIUnits.jl, this package encodes units in the type signature to
>>>>>> avoid run-time performance penalties. From there, the
>>>>>> implementations diverge. The package is targeted to Julia 0.5 / master,
>>>>>> as
>>>>>> there are some limitations with how promote_op is used in Julia 0.4
>>>>>> (#13803) <https://github.com/JuliaLang/julia/pull/13803>. I decided
>>>>>> it wasn't worth targeting 0.4 if the behavior would be inconsistent.
>>>>>>
>>>>>> Some highlights include:
>>>>>>
>>>>>> - Non-SI units are treated on the same footing as SI units, with
>>>>>> only a few exceptions (unit conversion method). Use whatever
>>>>>> weird units you want.
>>>>>> - Support for units like micron / (meter Kelvin), where some of
>>>>>> the units could cancel out but you don't necessarily want them to.
>>>>>> - Support for LinSpace and other Range types. Probably there are
>>>>>> still some glitches to be found, though.
>>>>>> - Support for rational exponents of units.
>>>>>> - Some tests (see these for usage examples).
>>>>>>
>>>>>> Please see the documentation for a comprehensive discussion,
>>>>>> including issues / to do list, as well as how to add your own units, etc.
>>>>>> Comments and feedback are welcome.
>>>>>>
>>>>>> Best,
>>>>>> Andrew Keller
>>>>>>
>>>>>
