[plt-scheme] Re: plt-scheme Digest, Vol 43, Issue 95
On Fri, Mar 27, 2009 at 9:59 AM, <plt-scheme-request at list.cs.brown.edu>wrote:
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> Today's Topics:
>
> 1. Re: expr-syntax-object-iterator: unknown expr:
> (#%variable-reference) (Matthew Flatt)
> 2. Re: Scheme and R (Neil Toronto)
> 3. Re: Scheme and R (Prabhakar Ragde)
> 4. Moby/Bootstrap talk slides (Shriram Krishnamurthi)
> 5. Re: Moby/Bootstrap talk slides (Marek Kubica)
> 6. Re: 3-D graphics (Matthias Felleisen)
> 7. Re: [plt-edu] Re: [plt-scheme] 3-D graphics (David Van Horn)
> 8. Re: Moby/Bootstrap talk slides (Shriram Krishnamurthi)
> 9. Typed Scheme misses some contract definition? (Paulo J. Matos)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Thu, 26 Mar 2009 13:30:00 -0600
> From: Matthew Flatt <mflatt at cs.utah.edu>
> Subject: Re: [plt-scheme] expr-syntax-object-iterator: unknown expr:
> (#%variable-reference)
> To: Tom Schouten <tom at zwizwa.be>
> Cc: plt-scheme at list.cs.brown.edu
> Message-ID: <20090326193000.ED7BE6500BC at mail-svr1.cs.utah.edu>
> Content-Type: text/plain; charset=UTF-8
>
> I fixed this in SVN by adding a case for `#%variable-reference' in
> `expr-syntax-object-iterator'.
>
> At Thu, 26 Mar 2009 14:13:10 +0100, Tom Schouten wrote:
> > Hello,
> >
> > In DrScheme, the following code produces no errors on "run":
> >
> > #lang scheme/base
> > (require html)
> > (read-html-as-xml (open-input-string "<html>"))
> >
> > but it does print out an error message on "debug":
> >
> > Welcome to DrScheme, version 4.1.5 [3m].
> > Language: Module; memory limit: 128 megabytes.
> > expr-syntax-object-iterator: unknown expr: (#%variable-reference)
> >
> > Cheers,
> > Tom
> >
> > _________________________________________________
> > For list-related administrative tasks:
> > http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>
>
> ------------------------------
>
> Message: 2
> Date: Thu, 26 Mar 2009 16:17:39 -0600
> From: Neil Toronto <ntoronto at cs.byu.edu>
> Subject: Re: [plt-scheme] Scheme and R
> To: Eli Barzilay <eli at barzilay.org>
> Cc: Prabhakar Ragde <plragde at uwaterloo.ca>,
> plt-scheme at list.cs.brown.edu
> Message-ID: <49CBFF03.5010402 at cs.byu.edu>
> Content-Type: text/plain; charset=us-ascii; format=flowed
>
> Eli Barzilay wrote:
> > On Mar 26, Neil Toronto wrote:
> >> As a language it's rather weak and inconsistent. Sungwoo Park's
> >> analysis is good, so I'll defer to him:
> >>
> >> http://www.postech.ac.kr/~gla/paper/R-ism-dec-8.ppt<http://www.postech.ac.kr/%7Egla/paper/R-ism-dec-8.ppt>
> >
> > If anything, reading this made me appreciate R more than my previous
> > vague impression. Specifically, that criticism reads very obviously
> > as an ML advocate criticising (PLT) Scheme.
>
> I got that impression as well, though R does have problems in the
> *areas* he points out. It rather reminds me of Wadler's critique of
> scheming, where the problems he pointed out were often problems for a
> different reason than he said.
>
> > Even more specifically:
> >
> > * We have a `void' value that is the common result of side-effect
> > functions[1] -- we even have (surprise) a `when' expression, and
> > one-sided `if's. (It's not clear to me whether R implements this
> > using a void value or using something like (values) -- but the
> > choice between the two is irrelevant.)
>
> In this case, he finally got to the real problem. It's not so much that
> "if" doesn't require an else branch or that a single-branch "if" returns
> NULL, but that the designers decided to make some uses of it "just work"
> by defining operations like this:
>
> > paste("Hello", NULL, "there", sep="|")
> [1] "Hello||there"
>
> So string-appending NULL appends nothing. But addition to it returns this:
>
> > NULL + 1
> numeric(0)
>
> where "numeric" creates a vector of zeros of the given length. The
> zero-length vector acts like a black hole in further math operations:
>
> > numeric(0) + 1
> numeric(0)
>
> Vectors are repeated if one vector argument is longer than the other,
> and give a warning if one length isn't a multiple of the other:
>
> > c(1, 2) + c(10, 20, 30, 40)
> [1] 11 22 31 42
> > c(1, 2, 3) + c(10, 20, 30, 40)
> [1] 11 22 33 41
> Warning message:
> In c(1, 2, 3) + c(10, 20, 30, 40) :
> longer object length is not a multiple of shorter object length
>
> (where "c" creates flat vectors) but the zero-length vector is treated
> specially with no warning or error at all:
>
> > numeric(0) + c(10, 20, 30, 40)
> numeric(0)
>
> I can see a train of thought leading to this overly forgiving and
> inconsistent state of affairs, and I think it derailed as soon as it set
> out.
>
> > * We have implicit boxing that allows `set!'. It's debatable whether
> > this is better than forcing an explicit `box' in the code (as ML
> > does), but again, with modules turning these into local boxes, the
> > difference is almost cosmetic[2].
> >
> > * Note that the "No Lexical Scoping" criticises the R repl in a way
> > that applies to any Scheme repl. The only difference is the `set!'
> > implying a definition (which is not a good idea in any case). Even
> > more importantly, it highlights the `let*' semantics of the OCaml
> > repl -- which is very problematic in itself (up to the point where I
> > just gave up on using the OCaml repl for anything more than simple
> > testing)[3]. The "Special Top Level?" slide is bogus for the same
> > reason.
>
> I agree about the top-level/repl thing, and yes the slide is bogus.
>
> I just realized why I missed a lot of the bogus arguments. It appears
> that Park attacked the semantics of R without understanding what they
> are. I think I missed that because I'm already familiar with R and have
> already seen the problem areas he points out, along with specific
> examples of the sweeping generalizations made on slide 26 (evidence of
> too many complex/special cases).
>
> Back to lexical scope. To get around = creating bindings and how that
> makes it difficult to mutate outer scope variables, R has a special
> assignment operator <<- that operates on the nearest outer scope. It
> also creates bindings there if they don't already exist. It's like
> Python's "global" but for any level. Funky.
>
> I agree with the rest of your analysis.
>
> Neil
>
>
> ------------------------------
>
> Message: 3
> Date: Thu, 26 Mar 2009 18:28:34 -0400
> From: Prabhakar Ragde <plragde at uwaterloo.ca>
> Subject: Re: [plt-scheme] Scheme and R
> To: Neil Toronto <ntoronto at cs.byu.edu>
> Cc: Eli Barzilay <eli at barzilay.org>, plt-scheme at list.cs.brown.edu
> Message-ID: <49CC0192.3030006 at uwaterloo.ca>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Neil Toronto wrote:
>
> > Back to lexical scope. To get around = creating bindings and how that
> > makes it difficult to mutate outer scope variables, R has a special
> > assignment operator <<- that operates on the nearest outer scope. It
> > also creates bindings there if they don't already exist. It's like
> > Python's "global" but for any level. Funky.
>
> There's something weird going on with scope in "lazy evaluation" in R.
> It's not lexical, but dynamic, and it's not clear to me when it flips
> from one to the other.
>
> It's fairly clear to me that the students in the stats course I'm
> talking about will not be dealing with most of these issues -- I think
> they're just asked to apply library functions without really
> understanding what they're doing. So the risk here is that in
> highlighting the similarities to Scheme -- and the differences from
> Scheme, which inevitably follow -- I would actually be doing them a
> disservice, relative to their prior blissfully ignorant state. --PR
>
>
> ------------------------------
>
> Message: 4
> Date: Thu, 26 Mar 2009 17:28:44 -0500
> From: Shriram Krishnamurthi <sk at cs.brown.edu>
> Subject: [plt-scheme] Moby/Bootstrap talk slides
> To: PLT Scheme ML <plt-scheme at list.cs.brown.edu>
> Message-ID:
> <c67d38c30903261528i11489acalad4cf29a140e4890 at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> After my keynote talk at yesterday's International Lisp Conference, a
> few people asked me for the talk slides. Better still, I made a
> personal audio recording as well. You can find both on the Web:
>
> http://www.cs.brown.edu/~sk/Publications/Talks/Moby-Bootstrap/<http://www.cs.brown.edu/%7Esk/Publications/Talks/Moby-Bootstrap/>
>
> The first release of the compiler will go out this weekend.
>
> Special thanks to Danny Yoo, who made the talk possible!
>
> Shriram
>
>
> ------------------------------
>
> Message: 5
> Date: Thu, 26 Mar 2009 23:47:12 +0100
> From: Marek Kubica <marek at xivilization.net>
> Subject: Re: [plt-scheme] Moby/Bootstrap talk slides
> To: Shriram Krishnamurthi <sk at cs.brown.edu>
> Cc: plt-scheme at list.cs.brown.edu
> Message-ID: <20090326234712.5916ba8b at halmanfloyd.lan.local>
> Content-Type: text/plain; charset=US-ASCII
>
> On Thu, 26 Mar 2009 17:28:44 -0500
> Shriram Krishnamurthi <sk at cs.brown.edu> wrote:
>
> > After my keynote talk at yesterday's International Lisp Conference, a
> > few people asked me for the talk slides. Better still, I made a
> > personal audio recording as well. You can find both on the Web:
> >
> > http://www.cs.brown.edu/~sk/Publications/Talks/Moby-Bootstrap/<http://www.cs.brown.edu/%7Esk/Publications/Talks/Moby-Bootstrap/>
>
> Could you post a PDF version of the slides too? I don't have Powerpoint
> and as a LaTeX/Beamer user have no desire to use OpenOffice.org either,
> since most slides are just PDF.
>
> Your topic sounds interesting and if I have some more time today, I
> might listen to the recording. I've hoped for some official recordings
> of all ILC talks.
>
> regards,
> Marek
>
>
> ------------------------------
>
> Message: 6
> Date: Thu, 26 Mar 2009 19:27:42 -0400
> From: Matthias Felleisen <matthias at ccs.neu.edu>
> Subject: Re: [plt-scheme] 3-D graphics
> To: John Clements <clements at brinckerhoff.org>
> Cc: Justin Phillips <jjustinphillipss at gmail.com>, PLT Scheme ML
> <plt-scheme at list.cs.brown.edu>
> Message-ID: <8C54869E-2CA5-45C1-B5D3-447A8747D184 at ccs.neu.edu>
> Content-Type: text/plain; charset=US-ASCII; delsp=yes; format=flowed
>
>
> Richard Cleis has done a first prototype of a 3D world/universe for
> us and send Eli and me great examples. If you want to work on this or
> if you are working on this, get in touch with him. I have run his
> beautiful 3D balloon examples and they are truly beautiful. -- Matthias
>
>
>
>
>
>
>
> On Mar 26, 2009, at 12:38 PM, John Clements wrote:
>
> >
> > On Mar 26, 2009, at 6:28 AM, Stephen Bloch wrote:
> >
> >> I attended a talk yesterday on using 3-D animation to teach
> >> mathematical concepts. The presenter was using either (a C/C++
> >> library named DarkGDK) or SecondLife, but I imagine a lot of the
> >> same things could be done with Alice. And if we perceive Alice as
> >> a serious competitor for "how to teach beginning programming," it
> >> would be nice if we could beat (or at least meet) her on her own
> >> turf -- fun, highly-motivating, attractive 3-D animation
> >> accessible to first-semester students.
> >>
> >> So there's this OpenGL binding bundled with PLT Scheme. Who out
> >> there has played with it? I'd like to write (or, even better, get
> >> somebody else to write!) a beginner-friendly, functional front end
> >> for it that allows first-semester students to build 3-D
> >> animations, with not much more difficulty than the 2-D animations
> >> we do with world, sb-world, or universe. Is anybody working on
> >> this sort of thing?
> >
> > It's ludicrously unfair of me to mention this before he's even
> > gotten started, but I'm working with an undergraduate (cc:'ed)
> > who's expressed an interest in bringing OpenGL into the FrTime
> > fold. If successful, this would probably fit extremely well with
> > the project you mention.
> >
> > John Clements
> >
> > _________________________________________________
> > For list-related administrative tasks:
> > http://list.cs.brown.edu/mailman/listinfo/plt-scheme
>
>
>
> ------------------------------
>
> Message: 7
> Date: Thu, 26 Mar 2009 19:42:26 -0400
> From: David Van Horn <dvanhorn at ccs.neu.edu>
> Subject: Re: [plt-edu] Re: [plt-scheme] 3-D graphics
> To: Geoffrey Knauth <gknauth at lycoming.edu>
> Cc: plt edu <plt-edu at list.cs.brown.edu>, PLT Scheme ML
> <plt-scheme at list.cs.brown.edu>
> Message-ID: <49CC12E2.4020200 at ccs.neu.edu>
> Content-Type: text/plain; charset=ISO-8859-1; format=flowed
>
> Geoffrey Knauth wrote:
> > While at Art and Code at CMU March 7-8, I learned CMU uses Processing
> > [1] for Intro to CS for non-majors [2], so if PLT develops a demo suite
> > rich with OpenGL examples, I think the examples in Processing would make
> > a good comparison. Processing's demos are fast enough I forget it's
> > Java underneath, and Processing syntax on the obnoxiousness scale is
> > less than Java and greater than Scheme.
> >
> > Geoff
> >
> > [1] http://processing.org/
> > [2] http://www.andrew.cmu.edu/course/15-100mooseNsquirrel/
>
> Ben Fry just gave a talk here at NEU on Processing. It started off very
> much like our intro course starts off on day 1 by programming with
> images in DrScheme, but rapidly went far beyond that while using 1-3
> line programs. It was too bad the PLT group was under represented, but
> there should be video of the event up soon on our student ACM chapter
> web page.
>
> If PLT could keep pace with Fry's first 10 minutes or so of examples, it
> would be quite appealing to students, in my opinion. Of course, all his
> stuff is imperative. If we had all the polished bells and whistles of
> Processing *and* the usual gang of functional abstractions, our freshmen
> could probably code circles around Fry.
>
> David
>
> http://acm.ccs.neu.edu/
>
>
> ------------------------------
>
> Message: 8
> Date: Thu, 26 Mar 2009 19:09:29 -0500
> From: Shriram Krishnamurthi <sk at cs.brown.edu>
> Subject: Re: [plt-scheme] Moby/Bootstrap talk slides
> To: Marek Kubica <marek at xivilization.net>
> Cc: plt-scheme at list.cs.brown.edu
> Message-ID:
> <c67d38c30903261709k4e6c660ap9e28a23e7d646e3a at mail.gmail.com>
> Content-Type: text/plain; charset=ISO-8859-1
>
> Thanks for your interest.
>
> Unfortunately, my talk involves numerous bits of relevant animation,
> some of which are quite precise. This does not translate well to PDF.
>
> I did load it today in OpenOffice to confirm that, though it does not
> come out perfectly, the outcome is quite reasonable.
>
> For the benefit of those with neither, I've uploaded the files to
> slideshare:
>
>
> http://www.slideshare.net/guest66441a/the-moby-scheme-compiler-for-smartphones
>
> This link is also on the talk's page.
>
> Enjoy!
>
> Shriram
>
>
> ------------------------------
>
> Message: 9
> Date: Fri, 27 Mar 2009 01:58:55 +0000
> From: "Paulo J. Matos" <pocmatos at gmail.com>
> Subject: [plt-scheme] Typed Scheme misses some contract definition?
> To: PLT-Scheme Mailing List <plt-scheme at list.cs.brown.edu>
> Message-ID:
> <11b141710903261858x3ff9a4e5s963910fb88d2a98d at mail.gmail.com>
> Content-Type: text/plain; charset=UTF-8
>
> Hi all,
>
> Assume I define test.scm:
> #lang typed-scheme
>
> (provide (struct-out foo))
>
> (define-struct: foo
> ((v : Integer)))
>
> I open another file xxx.scm:
> #lang typed-scheme
>
> (: v Integer)
> (define v 10)
>
> and I run it.
> On the interactions:
> Welcome to DrScheme, version 4.1.5.3-svn26mar2009 [3m].
> Language: Module; memory limit: 1024 megabytes.
> > (make-foo v)
> . typecheck: unbound identifier make-foo in: make-foo
> > (require "test.scm")
> > (make-foo v)
> - : foo2
> #<foo>
>
>
> However, If I add a require line to xxx.scm:
> #lang typed-scheme
>
> (require "test.scm")
>
> (: v Integer)
> (define v 10)
>
> interactions is now:
> Welcome to DrScheme, version 4.1.5.3-svn26mar2009 [3m].
> Language: Module; memory limit: 1024 megabytes.
> > (make-foo v)
> . typecheck: unbound identifier contract/proc in: (make-foo v)
> > (require "test.scm")
> > (make-foo v)
> . typecheck: unbound identifier contract/proc in: (make-foo v)
> >
>
> I don't know how typed-scheme works internally but I guess that the
> require line screws something up?
>
> Cheers,
>
> --
> Paulo Jorge Matos - pocmatos at gmail.com
> Webpage: http://www.personal.soton.ac.uk/pocm
>
>
> End of plt-scheme Digest, Vol 43, Issue 95
> ******************************************
>
--
http://www.watch-movies-online-hollywoodkiller.com
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