[Snow-users-list] some questions about snow

Marc Feeley feeley at iro.umontreal.ca
Thu Mar 15 21:59:22 EDT 2007

Hash: SHA1

These are all very important issues...

On 10-Mar-07, at 6:12 AM, Alexander Sepp wrote:

> hi,
> i'm new now to scheme, and of course snow. after fiddling around with
> snow and esp. gambit a while, i stumbled over some things that keep me
> thinking and grumbling. So i have few questions regarding the  
> scheme now
> framework:
> * Signature handling
> afaics, every file in a snowball archive has it's own signature.  
> why is
> this the case? wouldn't it be cleaner (and simpler) to provide the
> signature over the complete snowball archive itself? the problem is,
> that if i can not verify the origin of a tarball, i do not even  
> want to
> untar it.

The snowball structure is designed so that a package's parts can be  
contributed, and signed, by different people.  For example someone  
may be working on the Bigloo port while someone else is working on a  
Gambit port.  The maintainer can then collect these (separately  
signed) parts and just drop them into the package directory, then  
upload the package.

> * Performance
> i did some quick tests with the digest package. i noticed
> a performance drop of 2/3 using gambit compared to the version in
> ~~lib/digest.scm (delivered with the gambit system). how do i get the
> performance back, still using the snowball?

That is odd.  There is no reason why Snow packages should run  
slower.  I will investigate.

> * snow-* namespace
> if i want to use fixnum arithmetic, i have to write (snow-fxadd a b);
> wouldn't be (fxadd a b) simpler and maybe confrom to the upcoming  
> R6RS?
> the same holds for (snow-u8vector...). latter is from my point of view
> another workaround for various duplicated srfi's?

The "snow-XXX" name is used when there is a possible name conflict  
with an XXX operation on some Scheme system.  Often snow-XXX and XXX  
are related operations, but they may have slightly different  
semantics (accepted number of arguments, result in special cases,  
signaling of errors, etc).

I don't particularly like the "snow-" prefix and I hope that with  
time the Snow packages can deprecate those names when the various  
Scheme systems adopt a consistent semantics.  A good example is fx+,  
fx*, etc which should be standardized by R6RS.

> i hope these questions are not totally superfluous and already
> answered. i think the scheme now framework is a very clean approach to
> provide the fundamental base libraries needed by todays  
> applications. i
> also appreciate to see native scheme implementions of crypto
> algorithms. normally, there are only questionable ffi wrappers  
> provided.

Thanks.  It was a lot of work to write those algorithms in Scheme.   
The goal of course was to have a 100% pure Scheme implementation, so  
that snowman could do package signing and certificate management  
without requiring external tools (allowing one to run Snow on  
embedded systems for example).


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