Subject: [plt-scheme] gensym in r6rs? - msg#00109

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Re: [plt-scheme] Typed Scheme misses some contract definition?

This is a problem in the interaction between DrScheme and Typed Scheme. We have most of the architecture in place to fix this, but not all the pieces have been fitted into place. sam th On Fri, Mar 27, 2009 at 1:58 AM, Paulo J. Matos <pocmatos@xxxxxxxxx> wrote: > 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 > _________________________________________________ >  For list-related administrative tasks: >  http://list.cs.brown.edu/mailman/listinfo/plt-scheme > -- sam th samth@xxxxxxxxxxx _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

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Re: [plt-scheme] gensym in r6rs?

Hi Wolfgang, gensym seems to be thrown out of r6rs. Is there a standardized equivalent? The function gensym was not part of R5RS either. If you *really* wan't to use it, you could import gensym or string->uninterned-symbol from PLT's "scheme" language. But if you intend to use it to write macros, you ought to look into the syntax-case macro system instead. -- Jens Axel Søgaard _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

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[plt-scheme] Re: plt-scheme Digest, Vol 43, Issue 95

On Fri, Mar 27, 2009 at 9:59 AM, <plt-scheme-request@xxxxxxxxxxxxxxxxx> wrote: Send plt-scheme mailing list submissions to        plt-scheme@xxxxxxxxxxxxxxxxx To subscribe or unsubscribe via the World Wide Web, visit        http://list.cs.brown.edu/mailman/listinfo/plt-scheme or, via email, send a message with subject or body 'help' to        plt-scheme-request@xxxxxxxxxxxxxxxxx You can reach the person managing the list at        plt-scheme-owner@xxxxxxxxxxxxxxxxx When replying, please edit your Subject line so it is more specific than "Re: Contents of plt-scheme digest..." [Please handle PLT Scheme list administrative tasks through the Web:   http://list.cs.brown.edu/mailman/listinfo/plt-scheme] 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@xxxxxxxxxxx> Subject: Re: [plt-scheme] expr-syntax-object-iterator: unknown expr:        (#%variable-reference) To: Tom Schouten <tom@xxxxxxxxx> Cc: plt-scheme@xxxxxxxxxxxxxxxxx Message-ID: <20090326193000.ED7BE6500BC@xxxxxxxxxxxxxxxxxxxxx> 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@xxxxxxxxxx> Subject: Re: [plt-scheme] Scheme and R To: Eli Barzilay <eli@xxxxxxxxxxxx> Cc: Prabhakar Ragde <plragde@xxxxxxxxxxxx>,        plt-scheme@xxxxxxxxxxxxxxxxx Message-ID: <49CBFF03.5010402@xxxxxxxxxx> 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 > > 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@xxxxxxxxxxxx> Subject: Re: [plt-scheme] Scheme and R To: Neil Toronto <ntoronto@xxxxxxxxxx> Cc: Eli Barzilay <eli@xxxxxxxxxxxx>, plt-scheme@xxxxxxxxxxxxxxxxx Message-ID: <49CC0192.3030006@xxxxxxxxxxxx> 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@xxxxxxxxxxxx> Subject: [plt-scheme] Moby/Bootstrap talk slides To: PLT Scheme ML <plt-scheme@xxxxxxxxxxxxxxxxx> Message-ID:        <c67d38c30903261528i11489acalad4cf29a140e4890@xxxxxxxxxxxxxx> 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/ 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@xxxxxxxxxxxxxxxx> Subject: Re: [plt-scheme] Moby/Bootstrap talk slides To: Shriram Krishnamurthi <sk@xxxxxxxxxxxx> Cc: plt-scheme@xxxxxxxxxxxxxxxxx Message-ID: <20090326234712.5916ba8b@xxxxxxxxxxxxxxxxxxxxx> Content-Type: text/plain; charset=US-ASCII On Thu, 26 Mar 2009 17:28:44 -0500 Shriram Krishnamurthi <sk@xxxxxxxxxxxx> 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/ 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@xxxxxxxxxxx> Subject: Re: [plt-scheme] 3-D graphics To: John Clements <clements@xxxxxxxxxxxxxxxx> Cc: Justin Phillips <jjustinphillipss@xxxxxxxxx>,       PLT Scheme ML        <plt-scheme@xxxxxxxxxxxxxxxxx> Message-ID: <8C54869E-2CA5-45C1-B5D3-447A8747D184@xxxxxxxxxxx> 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@xxxxxxxxxxx> Subject: Re: [plt-edu] Re: [plt-scheme] 3-D graphics To: Geoffrey Knauth <gknauth@xxxxxxxxxxxx> Cc: plt edu <plt-edu@xxxxxxxxxxxxxxxxx>,        PLT Scheme ML        <plt-scheme@xxxxxxxxxxxxxxxxx> Message-ID: <49CC12E2.4020200@xxxxxxxxxxx> 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@xxxxxxxxxxxx> Subject: Re: [plt-scheme] Moby/Bootstrap talk slides To: Marek Kubica <marek@xxxxxxxxxxxxxxxx> Cc: plt-scheme@xxxxxxxxxxxxxxxxx Message-ID:        <c67d38c30903261709k4e6c660ap9e28a23e7d646e3a@xxxxxxxxxxxxxx> 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@xxxxxxxxx> Subject: [plt-scheme] Typed Scheme misses some contract definition? To: PLT-Scheme Mailing List <plt-scheme@xxxxxxxxxxxxxxxxx> Message-ID:        <11b141710903261858x3ff9a4e5s963910fb88d2a98d@xxxxxxxxxxxxxx> 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 _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme

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Re: [plt-scheme] gensym in r6rs?

Hi Wolfgang, gensym seems to be thrown out of r6rs. Is there a standardized equivalent? The function gensym was not part of R5RS either. If you *really* wan't to use it, you could import gensym or string->uninterned-symbol from PLT's "scheme" language. But if you intend to use it to write macros, you ought to look into the syntax-case macro system instead. -- Jens Axel Søgaard _________________________________________________ For list-related administrative tasks: http://list.cs.brown.edu/mailman/listinfo/plt-scheme