| Andrew Cooke | Contents | Latest | RSS | Twitter | Previous | Next

C[omp]ute

Welcome to my blog, which was once a mailing list of the same name and is still generated by mail. Please reply via the "comment" links.

Always interested in offers/projects/new ideas. Eclectic experience in fields like: numerical computing; Python web; Java enterprise; functional languages; GPGPU; SQL databases; etc. Based in Santiago, Chile; telecommute worldwide. CV; email.

Personal Projects

Lepl parser for Python.

Colorless Green.

Photography around Santiago.

SVG experiment.

Professional Portfolio

Calibration of seismometers.

Data access via web services.

Cache rewrite.

Extending OpenSSH.

Last 100 entries

The Black Dork Lives!; The UN Requires Unaninmous Decisions; LPIR - Steganography in Practice; How I Am 6; Clear Explanation of Verizon / Level 3 / Netflix; Teenage Girls; Formalising NSA Attacks; Switching Brakes (Tektro Hydraulic); Naim NAP 100 (Power Amp); AKG 550 First Impressions; Facebook manipulates emotions (no really); Map Reduce "No Longer Used" At Google; Removing RAID metadata; New Bike (Good Bike Shop, Santiago Chile); Removing APE Tags in Linux; Compiling Python 3.0 With GCC 4.8; Maven is Amazing; Generating Docs from a GitHub Wiki; Modular Shelves; Bash Best Practices; Good Emergency Gasfiter (Santiago, Chile); Readings in Recent Architecture; Roger Casement; Integrated Information Theory (Or Not); Possibly undefined macro AC_ENABLE_SHARED; Update on Charges; Sunburst Visualisation; Spectral Embeddings (Distances -> Coordinates); Introduction to Causality; Filtering To Help Colour-Blindness; ASUS 1015E-DS02 Too; Ready Player One; Writing Clear, Fast Julia Code; List of LatAm Novels; Running (for women); Building a Jenkins Plugin and a Jar (for Command Line use); Headphone Test Recordings; Causal Consistency; The Quest for Randomness; Chat Wars; Real-life Financial Co Without ACID Database...; Flexible Muscle-Based Locomotion for Bipedal Creatures; SQL Performance Explained; The Little Manual of API Design; Multiple Word Sizes; CRC - Next Steps; FizzBuzz; Update on CRCs; Decent Links / Discussion Community; Automated Reasoning About LLVM Optimizations and Undefined Behavior; A Painless Guide To CRC Error Detection Algorithms; Tests in Julia; Dave Eggers: what's so funny about peace, love and Starship?; Cello - High Level C Programming; autoreconf needs tar; Will Self Goes To Heathrow; Top 5 BioInformatics Papers; Vasovagal Response; Good Food in Vina; Chilean Drug Criminals Use Subsitution Cipher; Adrenaline; Stiglitz on the Impact of Technology; Why Not; How I Am 5; Lenovo X240 OpenSuse 13.1; NSA and GCHQ - Psychological Trolls; Finite Fields in Julia (Defining Your Own Number Type); Julian Assange; Starting Qemu on OpenSuse; Noisy GAs/TMs; Venezuela; Reinstalling GRUB with EFI; Instructions For Disabling KDE Indexing; Evolving Speakers; Changing Salt Size in Simple Crypt 3.0.0; Logarithmic Map (Moved); More Info; Words Found in Voynich Manuscript; An Inventory Of 3D Space-Filling Curves; Foxes Using Magnetic Fields To Hunt; 5 Rounds RC5 No Rotation; JP Morgan and Madoff; Ori - Secure, Distributed File System; Physical Unclonable Functions (PUFs); Prejudice on Reddit; Recursion OK; Optimizing Julia Code; Cash Handouts in Brazil; Couple Nice Music Videos; It Also Works!; Adaptive Plaintext; It Works!; RC5 Without Rotation (2); 8 Years...; Attack Against Encrypted Linux Disks; Pushing Back On NSA At IETF; Summary of Experimental Ethics; Very Good Talk On Security, Snowden; Locusts are Grasshoppers!; Vagrant (OpenSuse and IDEs); Interesting Take On Mandela's Context

© 2006-2013 Andrew Cooke (site) / post authors (content).

Getting Started with Gambit and Snow (or any other Scheme)

From: "andrew cooke" <andrew@...>

Date: Sun, 12 Aug 2007 20:04:09 -0400 (CLT)

This largely states the obvious, but boy, did I need this earlier today. 
So perhaps this will help someone else.

OK, so the context is - you want to use a Scheme.  You also want to be
able to use and share libraries.  And you want unit tests.  And you'd
rather not write code specific to one particular Scheme.  But you want
namespaces/packages...

So the solution, as far as I can see, is to use Snow (aka Scheme Now) -
http://snow.iro.umontreal.ca/ - plus whatever Scheme takes your fancy (I
am using Gambit because the idea of Erlang with a better syntax seems
pretty cool - if that makes no sense, check
http://lambda-the-ultimate.org/node/841).

But how does all this work?  That is the obvious thing that wasn't...

First, you install whatever Scheme you want (if you're running Linux you
may already have Guile installed).  I installed Gambit.  It's the usual
configure and make; pretty painless.

Next, you install Snow.  That means downloading the "generic Snow" and
then doing the config and make install process.

One you've done that (and set your paths), you end up with a couple of
utilities.  First, snowman, which is like yast or apt, or rpm or cspan,
whatever - a package manager that lets you install packages.  It's
documented 2/3 of the way down this page:
http://snow.iro.umontreal.ca/?tab=Documentation

Second, you have a program called "snow" which is what you use to invoke
your scheme code.  I wasn't expecting this, but it makes sense - it hides
away whatever magic is needed to convert your particular Scheme to support
the cross-platform snow API.

The simplest way to use snow is as an interpreter (you can also compile
code using "snow --compile" but I've not explored that yet).  The Snow
docs give the following example.  Note that the first line is some kind of
bash magic that invokes the same file using "snow" (I think it is written
like that so that the syntax is acceptable to bath bash and scheme).

":";exec snow -- "$0" "$@"

(package* go/v1.0.0
 (require: hostos/v1)
 (require: fixnum/v1))

(define (double x)
  (snow-fxarithmetic-shift-left x 1))

(test* (expect* (= 8 (double 4))))

(write (double (string->number (cadr (snow-command-line)))))
(newline)

To see that working, put it in a file called "go.scm", then chmod +x so
that it's executable, and invoke it with an argument:

> ./go.scm 500
1000

That's it, really.  That is running (in my case) Gambit, with all the
relevant Snow bits added.  So you get the module/namespace functionality
(the package* bit) and the unit test functionality (test*, expect*).

One final cute trick.  I said earlier that Guile is probably already
installed on Linux.  That's true in my case, and Snow can invoke scripts
on "all schemes", which makes testing compatibility easy.  Here's how:

> SNOW_HOST=all ./go.scm 500
------------------------------------------------------------ gambit
1000
------------------------------------------------------------ guile
1000

Once you grok the above, the Snow site documentation makes a lot more
sense.  All this is there anyway (what got me started was someone sending
me a cut+paste of the relevant sections!).  But somehow, for me at least,
the "big picture" took time to form.

Andrew

Comment on this post