gmane.comp.lang.racket.user

classroom response system

Danny Heap — 2013-05-17T20:36:57

A colleague has developed a classroom response tool that allows
students to download exercises, write solutions, and then either
visualize the execution of their solution or run unit tests, and then
submit their solution.  The instructor can display a histogram of of
the submissions that passed various tests, and then sample some of the
interesting examples to discuss with the class (all this assumes
wireless coverage for the classroom).

This is currently implemented for Python, but my colleague wants to
extend it to other languages.  He has a student looking into the
feasibility of implementing it for DrRacket, with the rough idea
being:

-- Students and instructors run local instances of DrRacket
           (hence access to the Stepper for student languages)
-- Run the tests either client- or server-side in a sandbox
-- Get files to/from DrRacket to server somehow

Since either students or the instructor will want to load files that
are stored remotely (either starter code for exercises or student
subm

Duplicating output from a system call

Nick Shelley — 2013-05-16T20:12:51

I have a script that runs some automated tests and logs the results to the
console. The tests can take 10+ minutes, so logging steps to the console is
informative. I'm using Racket to run the script with (system ...) and parse
the logs and report pass/failure, but to do that I have to capture the
logs. I spent about an hour in the port docs and can't figure out how to
both log to the console and capture the logs in Racket for further
processing (although I'm really good at missing the obvious).

My current workaround is to use the tee command when running the script and
then read in and process the file afterwords, but I was wondering if there
is a more direct way to do this in Racket.
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Unicode character name

Manfred Lotz — 2013-05-15T17:24:22

Having a unicode character is there a function to retrieve the
character's name?

Example: U+0907 gives DEVANAGARI LETTER I

connectivity with AWS and S3?

Geoffrey S. Knauth — 2013-05-14T21:25:33

I have a new potential project starting and I have my choice of language.  It will be doing a lot of web navigation (as a user would, just faster) and it has to run in an AWS [1] environment and interact with AWS S3 buckets [3].  I know I can do this with Scala or Python, but there are aspects of the project that make Racket seem appealing, if I can be confident the AWS integration will be solid.  I suppose I could just use FFI to integrate with any existing libraries in other languages that talk to AWS.  My question is, is there anyone else out there in Racket-land who has used AWS as part of the application?  I'll be running on AWS hardware and some of the big files will have to be stored on S3.

I'm also probably going to make heavy use of JSON.  The last time I did anything webby in Racket it was using XML, and JSON is dead simple by comparison.  I just want reassurance that the Racket JSON support I found [3] is reasonably mature.  Another question of a web services nature:  does Racket now handle web r

Maybe self-inclusion should be forbidden

Alfred Zhong — 2013-05-14T18:13:33

Hi Dear Racket experts,

I once accidentally include a file in itself like:

In foo.scm

(include "foo.scm")


And it causes infinite loop. Maybe this should be forbidden in the language
spec.

Thanks,
Alfred
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getting remote ip address

prad — 2013-05-14T18:07:01

in php i can do this:
$ip=$_SERVER['REMOTE_ADDR'];

to find out what the client ip address is.

how do i do it in racket?

i looked at request-client-ip provided by
web-server/http/request-structs
but that seems to require i run the racket webserver.

Kernel size for flomap-gaussian-blur

2013-05-11T19:56:28

Hi. Can't find convolution kernel dimensions in the docs, neither they can be
specified via arguments.

Any ideas what they are?

Thanks.

Call for Papers: Workshop on Functional Art, Music, Modeling, and Design (colocated with ICFP)

Brent Yorgey — 2013-05-13T20:44:35

======================================================================
      FARM 2013: Call for Papers

  ACM SIGPLAN Workshop on Functional Art, Music, Modeling and Design
      Boston, Massachusetts, USA
      28th September, 2013 (directly after ICFP)

      http://www.cis.upenn.edu/~byorgey/farm13/
======================================================================

Scope
-----

The functional programming community is largely interested in writing
beautiful programs. This workshop is intended to gather researchers and
practitioners interested in writing beautiful programs that generate
beautiful artifacts. Such artifacts may include visual art, music, 3D
sculptures, animations, GUIs, video games, physical models,
architectural models, choreographies for dance, poetry, and even
physical objects such as VLSI layouts, GPU configurations, or mechanical
engineering designs. The framework used need not be purely functional
(“mostly functional” is fine); may be based on abstractions such as
higher

Question about resolution of variable-name conflicts innamespaces

Matthew Butterick — 2013-05-14T16:09:02

Suppose x-is-foo.rkt is this:

(module x-is-foo racket
  (define x 'foo)
  (provide x))

If you open another file and try this:

(require "x-is-foo.rkt")
(define x 'bar)

You'lll get a "identifier already imported" error. OK, that much I
understand.

Here's the question. When you do this:

(parameterize ([current-namespace (make-base-empty-namespace)])
  (namespace-require 'racket)
  (namespace-require "x-is-foo.rkt")
  (namespace-set-variable-value! 'x 'bar)
  (eval '(print x) (current-namespace)))

This time, you get 'foo. Why 'foo? Why not another "identifier already
imported" error?

I assume I'm missing a subtlety of how the namespace environment is
different. But according to the docs, both namespace-require and
namespace-set-variable-value! affect the top-level environment of the
namespace. So I don't see why the require is silently overriding the
set-variable-value, rather than causing a conflict.

It's not a sequencing issue, because if you swap the two lines:

(parameterize ([current-namespace (mak

Bootstrap teachpacks

Lawrence Bottorff — 2013-05-14T15:36:53

Is there any documentation on how to set up and run Bootstrap lessons using
DrRacket? For example, I'm trying through DrRacket to install the
downloaded teachpack for Bootstrap and I get:

default-load-handler: cannot open input file
  path:
/home/borgauf/.racket/5.3.3/collects/installed-teachpacks/bootstrap-common.rkt
  system error: No such file or directory; errno=2

Thanks,
LB
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eval function works at REPL but not in file

Alfred Zhong — 2013-05-14T11:01:51

Hi Racket experts,

I am reading SICP and trying this piece of code using Racke:

(define (definition-value exp)
    (if (symbol? (cadr exp))
        (caddr exp)
          (make-lambda
            (cdadr exp) ; formal parameters
               (cddr exp)  ; body
        )
    )
)

(define (make-lambda parameters body)
    (cons 'lambda (cons parameters body))
)

(  (eval  (definition-value '(define (double x) (+ x x))) ) 10)

In REPL, it return 20 with no problem.

However, if I put it into a file and use racket command to run it (with
#lang scheme in the file)

it complains:
compile: unbound identifier (and no #%app syntax transformer is bound) at:
lambda in: (lambda (x) (+ x x))

Do you have any idea what happened there? How can I solve this problem?

Thanks,
Alfred
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How to connect to twitter streaming API?

SD — 2013-05-14T08:46:00

Dear All,
This is my first message here, and first of all thank you for the excellent
documentation already available.

I tried to browse the past messages and the documentation available online
but I couldn't find any information on how to query the twitter streaming
API. I'm interested in getting JSON messages that meet certain criteria
from the filtering API:
https://dev.twitter.com/docs/api/1.1/post/statuses/filter
(notice the POST here).

Do you have any experience with this?

Thanks,
SD
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Intro Project: Racket support in MediaWiki's GeSHihighligher

Tim Brown — 2013-05-14T08:09:18

Folks,

I have notified the GeSHi and Rosetta Code (a user of MediaWiki) of my
racket.php script, and have made it a personal mission to poke them every
week or so. However, they are both very busy and assure me that integrating
it *is* on their to do lists.

I have put a note on the Intro Projects Wiki page to this effect; I hope
nobody objects.

FYI racket.php can be found at
https://github.com/tim-brown/geshi-racket/blob/master/racket.php
and you can put it into your GeSHi syntaxes directory if you want to use/
test it.

Tim

random: lambda on the mountain

Danny Yoo — 2013-05-13T21:52:43

https://plus.google.com/117593568781545916065/posts/GfaAnrH2xLk

I wish I could have captured it better on camera.
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(no subject)

Cody Goodman — 2013-05-13T09:45:32

Hello, can anyone offer an idiom/thinking process/approach critique on my
code below? I'm new to racket and trying to program in racket, not program
python in racket syntax ;)

#lang racket
(require json)
(require net/url)

(define data-set
  (let* (
         ;; Turn url into a net/url-struct so you can allow a different
search query as well as other customizations
         ;; easily.
         [api-url (string->url "
http://gdata.youtube.com/feeds/api/videos/?alt=json&v=2&category=Movies&q=Inception
")]
         ;; figure out how to use call/input url
         [in (get-pure-port api-url #:redirections 2)]
         [json-blob (read-json in)])
    (close-input-port in)
    json-blob))

(struct movie (title price link))
(define movies (hash-ref (hash-ref data-set 'feed) 'entry))

(define (make-movie movie-result)
  (let* (
         [title (hash-ref (hash-ref movie-result 'title) '$t)]
         [price (with-handlers ([exn:fail? (lambda (exn) 0)])
                  (hash-ref (car (hash-ref (hash-ref movie-result

FFI

Kubilay Kaan — 2013-05-13T08:58:46

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Trouble with RSound

Gabriel Peredo — 2013-05-12T19:26:21

Hello,

I'm trying to use RSound, but I ran into a problem. Thing is, if I try
to play more than one sound, in any manner, during a single racket
session, I get a "pa-open-stream: Device unavailable" error. This here
is enough to trigger the problem on my machine:

#lang racket
(require (planet clements/rsound))
 
(play ding)
(play ding)

For what it's worth, here is some info about my system:

Fedora 17, x86_64
Racket 5.3
portaudio v19 (from Fedora's repo)
RSound v4.4

Thanks in advance.

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thread size and creation time

Berthold Bäuml — 2013-05-11T10:17:28

Hi,

what is the reason that threads in Racket are so much bigger than in Gambit Scheme and take so much longer to create them? Is there possibly a way to come closer to Gambit performance or have threads in Gambit less functionality? In my little Racket test program below I get about 10kB per thread on my MacBook and creation takes about 100us per thread (Gambit claims to fit "millions of active threads in ~1GB and a creation time of 0.5us).

Marc Freely states in a talk from 2010 about Gambit http://www.iro.umontreal.ca/~gambit/Gambit-inside-out.pdf

Green threads
Preemptive scheduler with priorities
Very lightweight and scalable
Thread = descriptor (324 bytes) + continuation 
Thread creation/synchronization ~ 0.5 μs 
O(log N) enqueue/dequeue operations 
Supports millions of active threads (in ~ 1GB)


Best,
Berthold

Racket 5.3.4 doesn't build aginst libpng 1.6

Eric Bélanger — 2013-05-10T22:23:01

I'm trying to build racket 5.3.4 but I'm getting many similar errors:
png_structp->C: argument is not non-null `png_structp' pointer
  argument: #f

I found out that this only happens with libpng 1.6.2. It builds fine if I
use libpng 1.5.15.

Does anyone have a fix?

Thanks.
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SSL and db/postgresql performance

Neil Van Dyke — 2013-05-10T20:28:13

Anyone run into any unusual performance problems when using SSL with a 
"db/postgresql" connection, or have ideas why that might happen?

Reason I ask is that a particular large Racket installation has reported 
a problem, and I have only a few guesses as to why.  This installation 
has two libraries for accessing PostgreSQL: an old one using a C 
extension and "libpq", and a drop-in replacement that layers over the 
Racket "db" library.  When SSL is not used, the new library gives vastly 
better performance under load, perhaps due mostly to no C mutual 
exclusion bottleneck when handling concurrent connections.  However, 
when the connections are SSL'd, the relative performance difference 
becomes reversed, and the old library with "libpq" C extension library 
becomes much faster than the one using Racket "db".  The SSL protocol 
versions should be the same.

Assuming that the performance difference is not due to a configuration 
difference or experimental error... my first guess would be a huge 
latency di

making a windows exe file

Kejia柯嘉 — 2013-05-10T17:25:49

hi,

i build my racket program to win7 execution file, but it needs some
dll on another win7 machine: cannot load dll libracket3m_8bh3lk.dll.
how can i build a standalone distribution program include all
dependencies for my case?

------------------
daniel
☵☯☲

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