[racket] users Digest, Vol 109, Issue 75

Please take me off the list

Thanks

On Mon, Sep 29, 2014 at 10:32 AM,  <users-request at racket-lang.org> wrote:
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> Today's Topics:
>
>    1. Re: canonical index of Racket courses? [was: Summer programs
>       learning Racket for a student] (jab at math.brown.edu)
>    2. Re: typed racket, filters, and polymorphism (Konrad Hinsen)
>    3. Re: aws/glacier: credential scope (Greg Hendershott)
>    4. rsound docs (C K Kashyap)
>    5. Re: typed racket, filters, and polymorphism (Robby Findler)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sun, 28 Sep 2014 23:36:05 -0400
> From: jab at math.brown.edu
> To: Sam Tobin-Hochstadt <samth at cs.indiana.edu>, Matthias Felleisen
>         <matthias at ccs.neu.edu>
> Cc: Racket Users <users at racket-lang.org>
> Subject: Re: [racket] canonical index of Racket courses? [was: Summer
>         programs learning Racket for a student]
> Message-ID:
>         <CANwREeXtCqExVYCchvg4pvqFWs06tb4b=jtmU5zpdwTsAaM4Hg at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> On Wed, Sep 17, 2014 at 10:51 AM, Sam Tobin-Hochstadt <samth at cs.indiana.edu>
> wrote:
>
>> I've now created a wiki page for this, with some initial content:
>> https://github.com/plt/racket/wiki/Courses-using-Racket
>>
>
> And now it's up to 22 revisions! Thanks for creating, Sam, and to everyone
> who added to it.
>
> On Tue, Sep 16, 2014 at 8:43 PM, Matthias Felleisen
>> <matthias at ccs.neu.edu> wrote:
>> > Do you imagine listing college courses such as Brown's 17, which uses
>> > DrRacket and the teaching languages? Or do you want Coursera courses that
>> > everyone can access?
>>
>
> I think linking to any class that makes educational materials publicly
> available is valuable, but they should be divided into one section for
> classes that don't require being admitted into a larger institution to
> participate in (e.g. Bootstrap World, Coursera, summer programs for teens,
> etc.), and another section for those that do.
>
>
>> > And yes, we should probably create a wiki like thing for such an effort
>> or
>> > perhaps something like packages.racket-lang.org. I'll bring it up as we
>> meet
>> > in St Louis.
>>
>
> Thanks, Matthias, and hope you all had a great time in St Louis. Looks like
> it was a wonderful conference.
>
> Can the wiki page above be directly linked off racket-lang.org, perhaps a
> bit more prominently? I hadn't even noticed
> https://github.com/plt/racket/wiki before; now I see the link to it kind of
> buried under the Contributing column of the Community section. Perhaps it's
> not easy to find for others too.
>
> Thanks again for following up on this.
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> ------------------------------
>
> Message: 2
> Date: Mon, 29 Sep 2014 10:44:56 +0200
> From: Konrad Hinsen <konrad.hinsen at fastmail.net>
> To: racket users list <users at racket-lang.org>
> Subject: Re: [racket] typed racket, filters, and polymorphism
> Message-ID:
>         <21545.7176.252047.613404 at Ordinateur-de-Catherine-Konrad.local>
> Content-Type: text/plain; charset=us-ascii
>
> Matthias Felleisen writes:
>
>  > Your message points out where gradual typing badly fails.
>
> Not just gradual typing. I am not aware of any good unit
> implementation in any type system, with the exception of F# and Frink
> whose type systems were explicitly modified to add unit checking as a
> special case. Dependent types should permit a good solution, but I
> haven't seen it done yet.
>
> The reason you need dependent types is that the product of two
> measures is another measure with a new unit, so you must be able to
> construct new types (representing units) from values. For example, a
> length divided by a time yields a speed. Once you can do that, scaling
> a unit (e.g. from meters to kilometers) becomes a special case.
>
>  > In this specific case, you have two aspects of dimensionality:
>  > dimension per se (I am sure there is a word for it) and the chosen
>  > unit to represent it.
>
> The two terms used for this distinction are in fact "dimension" and
> "unit".
>
>  > If someone writes (area-of-rectangle 1 [mm] 1 [km]), there is
>  > nothing wrong with it -- except that the type checker should insert
>  > a coercion from mm to m and from km to m (multiplying/dividing by
>  > 1,000).
>
> That's a topic of hot debate in the scientific computing community.
> Some argue that the type checker should consider your example as an
> error, and not do any implicit conversion. The motivation is that the
> expression you used is more likely to be a mistake than the meaningful
> use of expressive language, since best practices recommend to use a
> minimal set of units inside any piece of code.
>
> Anyway, that's a minor detail. If your type system can handle
> automatic conversion, then it can also handle its absence.
>
>
> Alexander D. Knauth writes:
>
>  > What I had in mind was for the structs to be available at run-time,
>  > but that ideally the optimizer could take them out for the
>  > intermediate operations and put them back for the final result.
>
> You are actually adding a very Racket-specific requirement to the
> already difficult units-as-types problem: the interplay between a
> typed and an untyped dialect of the same language. I agree this would
> be nice to have.
>
> Konrad.
>
>
> ------------------------------
>
> Message: 3
> Date: Mon, 29 Sep 2014 09:13:11 -0400
> From: Greg Hendershott <greghendershott at gmail.com>
> To: Norman Gray <norman at astro.gla.ac.uk>
> Cc: users at racket-lang.org
> Subject: Re: [racket] aws/glacier: credential scope
> Message-ID:
>         <CAGspUn1Q5MvFq4i6q3KuoxBcszOpTh-RdjL=QWy+JbwHUUrXSA at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> It looks like the package server did eventually refresh a few hours ago:
>
>     Last Updated:  9/28/2014, 4:21:56 PM  ;change on GitHub
>     Last Checked:  9/29/2014, 7:51:37 AM  ;pkgs.r-l.org refresh
>
> (I believe those times are US MT, -0600.)
>
> On Sun, Sep 28, 2014 at 6:10 PM, Greg Hendershott
> <greghendershott at gmail.com> wrote:
>> If you're in a hurry you could remove and re-install directly from GitHub:
>>
>>  $ raco pkg remove aws
>>  $ raco pkg install git://github.com/greghendershott/aws
>>
>> On Sun, Sep 28, 2014 at 5:40 PM, Norman Gray <norman at astro.gla.ac.uk> wrote:
>>>
>>> On 2014 Sep 28, at 22:17, Greg Hendershott <greghendershott at gmail.com> wrote:
>>>
>>>>>> I clicked "update" on pkgs.racket-lang.org. But it seems to be slower
>>>>>> than usual to refresh. After it does, you can `raco pkg update aws` to
>>>>>> get the fix.
>>>>>
>>>>> Something seems wrong/stuck on pkgs.racket-lang.org. The top of the page says:
>>>>>
>>>>>  "update upload in progress: there may be inconsistencies below"
>>>>>
>>>>> It's been saying that for nearly an hour.
>>>>
>>>> Sometimes instead it says:
>>>>
>>>>  "update upload being computed: the information below may not
>>>> represent all recent changes and updates"
>>>>
>>>> It has switched between those two messages at various intervals over
>>>> the last hour.
>>>
>>> And in case it's a useful data point, I'm getting
>>>
>>> % raco pkg update aws
>>> Resolving "aws" via http://download.racket-lang.org/releases/6.1/catalog/
>>> Resolving "aws" via http://pkgs.racket-lang.org
>>> No updates available
>>> %
>>>
>>> And Greg, your fix is close enough to what I guessed might be the problem that I'm now kicking myself for not just diving in and trying a fix myself.  Garhhhh...
>>>
>>> Norman
>>>
>>>
>>> --
>>> Norman Gray  :  http://nxg.me.uk
>>> SUPA School of Physics and Astronomy, University of Glasgow, UK
>>>
>
>
> ------------------------------
>
> Message: 4
> Date: Mon, 29 Sep 2014 19:09:17 +0530
> From: C K Kashyap <ckkashyap at gmail.com>
> To: users at racket-lang.org
> Subject: [racket] rsound docs
> Message-ID:
>         <CAGdT1gq=E_-O9JcnaMnOEQkEK51vWxdPsFHHNSudzRoJCwHm2g at mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
>
> Hi,
>
> I saw this nice racketcon video (
> https://www.youtube.com/watch?v=DkIVzHNjNEA&list=PLXr4KViVC0qI9t3lizitiFJ1cFIeN2Gdh&index=9)
> on rsound. I've installed the rsound package and have been able to run the
> example from the video.
>
> Is there a place that has mode documentation/tutorial on rsound?
>
> Regards,
> Kashyap
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> ------------------------------
>
> Message: 5
> Date: Mon, 29 Sep 2014 09:32:40 -0500
> From: Robby Findler <robby at eecs.northwestern.edu>
> To: Konrad Hinsen <konrad.hinsen at fastmail.net>
> Cc: racket users list <users at racket-lang.org>
> Subject: Re: [racket] typed racket, filters, and polymorphism
> Message-ID:
>         <CAL3TdONRKwUJ0pV3WhXDQvRgMT6mhSp6D6QGr4=W4y7g7DsK4w at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> Just in case, here is one piece of related work from the PL world and
> is probably a reasonable starting point for finding others' attempts
> at this problem:
>
> http://research.microsoft.com/en-us/um/people/akenn/units/
>
> Robby
>
>
> On Mon, Sep 29, 2014 at 3:44 AM, Konrad Hinsen
> <konrad.hinsen at fastmail.net> wrote:
>> Matthias Felleisen writes:
>>
>>  > Your message points out where gradual typing badly fails.
>>
>> Not just gradual typing. I am not aware of any good unit
>> implementation in any type system, with the exception of F# and Frink
>> whose type systems were explicitly modified to add unit checking as a
>> special case. Dependent types should permit a good solution, but I
>> haven't seen it done yet.
>>
>> The reason you need dependent types is that the product of two
>> measures is another measure with a new unit, so you must be able to
>> construct new types (representing units) from values. For example, a
>> length divided by a time yields a speed. Once you can do that, scaling
>> a unit (e.g. from meters to kilometers) becomes a special case.
>>
>>  > In this specific case, you have two aspects of dimensionality:
>>  > dimension per se (I am sure there is a word for it) and the chosen
>>  > unit to represent it.
>>
>> The two terms used for this distinction are in fact "dimension" and
>> "unit".
>>
>>  > If someone writes (area-of-rectangle 1 [mm] 1 [km]), there is
>>  > nothing wrong with it -- except that the type checker should insert
>>  > a coercion from mm to m and from km to m (multiplying/dividing by
>>  > 1,000).
>>
>> That's a topic of hot debate in the scientific computing community.
>> Some argue that the type checker should consider your example as an
>> error, and not do any implicit conversion. The motivation is that the
>> expression you used is more likely to be a mistake than the meaningful
>> use of expressive language, since best practices recommend to use a
>> minimal set of units inside any piece of code.
>>
>> Anyway, that's a minor detail. If your type system can handle
>> automatic conversion, then it can also handle its absence.
>>
>>
>> Alexander D. Knauth writes:
>>
>>  > What I had in mind was for the structs to be available at run-time,
>>  > but that ideally the optimizer could take them out for the
>>  > intermediate operations and put them back for the final result.
>>
>> You are actually adding a very Racket-specific requirement to the
>> already difficult units-as-types problem: the interplay between a
>> typed and an untyped dialect of the same language. I agree this would
>> be nice to have.
>>
>> Konrad.
>> ____________________
>>   Racket Users list:
>>   http://lists.racket-lang.org/users
>
>
> End of users Digest, Vol 109, Issue 75
> **************************************