Re: Monads and Linear Logic

1997-09-09 Thread S. Doaitse Swierstra

At 8:08 PM 9/3/97, Patrick Logan wrote:
I am stretching my imperative brain cells to comprehend(!) monads, and
now their relationship to linear ("unique" in Clean) objects. I have
glanced at Philip Wadler's paper, but the semantics are impenetrable
to me at this point, and I am looking at the issue from a more
"practical" point of view ("practical" in the sense of "practice",
"practitioner", not that theory is impractical!).

My impression is that monads and linear objects are used in
essentially the same way. I have explicitly read how linear objects
allow the compiler to "garbage collect" them at compile time because
the compiler knows exactly how they are used. I assume the same can be
done for monads? Is this done in the good Haskell compilers?

It has gone unnoticed by many that an assignment not only assigns a new
value to a variable, but is at the same time a form of static garbage
collection. The programmer implicitely states explicitely that the old
value is no longer of interest. This is were state-monads and
uniqueness-types coincide.

  Doaitse Swierstra


In general laymen's terms, what are the performance and expressiveness
issues in comparing monads with linear objects?

Thanks
--
Patrick Logan mailto:[EMAIL PROTECTED]
Voice 503-533-3365Fax   503-629-8556
Gemstone Systems, Inc http://www.gemstone.com

__
S. Doaitse Swierstra, Department of Computer Science, Utrecht University
(Prof. Dr)P.O.Box 80.089, 3508 TB UTRECHT,   the Netherlands
  email: [EMAIL PROTECTED]
  WWW:   http://www.cs.ruu.nl/
  PGP Public Key: http://www.cs.ruu.nl/people/doaitse/
  tel:   +31 (30) 253 3962, fax: +31 (30) 2513791
__^___^___







Announcing TkGofer Version 2.0

1997-09-09 Thread Koen Claessen


We are pleased to announce the official 2.0 release of TkGofer.

TkGofer is a library (a prelude file) of functions for writing
graphical user interfaces in the functional language Gofer.

The new version 2.0 includes:

  - A limited but useful form of concurrency.
The functions and types are based on Concurrent Haskell.
They include:

  fork :: GUI a - GUI ()

  type MVar; newMVar, takeMVar, putMVar
  type CVar; newCVar, takeCVar, putCVar

  - A large library of file and user IO functions.
The function names in this library are based on the io library
provided by Hugs. New features include:

  readFile, writeFile, appendFile,
  openFile, hPutStr, hGetString, hSeek
  
  - The widget structure has been cleared up and there are some extra
widgets defined. Embedded windows are now possible too.

TkGofer is available through the WWW from

  http://www.informatik.uni-ulm.de/pm/ftp/tkgofer.html

We are working on porting TkGofer to Hugs, but we are still
waiting for Hugs to get multiple parameter type classes. :)

For specific questions you may mail to

Ton Vullinghs ([EMAIL PROTECTED])
or Koen Claessen ([EMAIL PROTECTED]).







IEEE Expert - Reminder

1997-09-09 Thread Alberto Broggi


 R E M I N D E R 
The deadline for submitting tutorials or surveys proposals is 
approaching. Please help distributing this announcement,
Best Regards,   Alberto Broggi
   
=


 C   A   L   L   F   O   R   A   R   T   I   C   L   E   S

IEEE Expert Magazine


 VISION-BASED DRIVING ASSISTANCE IN VEHICLES OF THE FUTURE
   http://www.ce.unipr.it/expert

   ALBERTO BROGGI,  Guest Editor

 Thanks to the increasing computational power of current computer systems
 and to the reduced costs of image-acquisition devices, in  the last  few
 years vision-based sensing of the surrounding environment has  gained  a
 strategic importance not only in military applications, but also in  the
 automotive field. This  special  issue  will  address  the  problems  of
 autonomous vehicle driving, describe common techniques,  and present the
 state of the art. Suggested topics include

 -  Vision-based guidance of unmanned vehicles.
 -  Analysis of real-time constraints for vehicle driving.
 -  Vehicle navigation in unknown environments.
 -  Integration of specialized hardware on vehicles.
 -  Description of research prototypes.
 -  Legal aspects.
 -  Analysis of future trends.

 Expert seeks two kinds of articles:

 -  TUTORIALS and SURVEYS introducing this field and reviewing the  state
of the art or the state of the practice of work done  in  this  area,
with the aim of comparing different solutions  and  techniques.  Such
articles should be approximately 6,000 words (9-10  magazine  pages),
with extensive references to widely available published works. One or
two such articles will likely be included.

 -  ARTICLES  describing  prototypes  of  autonomous  vehicles  developed
worldwide  by  universities,  research  centers,  corporations,   and
government institutions.  These articles  should  describe  both  the
techniques and the results obtained, and the references should  allow
the interested reader to follow up on both. Articles  describing  the
fusion of data coming from sensors other than vision are also welcome.
 These articles should be from 5,500 to 6,000 words (8-9 magazine
pages), with no more than 12 references. A consistent and useful  set
of definitions and examples can often  help  explain  the  underlying
mathematics. Such aids can be presented as sidebars in the  published
article. Four or five such articles will likely be included.

 All authors should submit six hard copies of their article  by  December
 20, 1997, to the guest editor,  Alberto Broggi.   Authors  intending  to
 submit tutorials or survey articles are encouraged to discuss this  with
 the guest editor  or to send an extended abstract to him  by  October 1,
 1997.

 Guest Editor:  Alberto BROGGI
Dipartimento di Ingegneria dell'Informazione
Universita` di Parma
I-43100 Parma
ITALY
Fax 39 (521) 90-5723
[EMAIL PROTECTED]

 Schedule:
   Submission of manuscripts: December 20, 1997
   Acceptance/rejection notification: April 12, 1998
   Revised manuscripts due:   June 7, 1998
   Publication:   September 1998

 For more information, access http://www.ce.unipr.it/expert

 IEEE  Expert:  Intelligent  Systems  and  Their  Applications   publishes
 technically substantive articles that are referenced extensively  in  the
 literature and read by 8,000-9,000 people worldwide. Expert is a magazine
 of applied AI - a bridge  between  the  research community  and the  user
 community.  Its readers  want  to  learn  about  the  tools,  techniques,
 concepts, and systems that have potential for real-world applications.
 Conceptual or theoretical papers are welcome, provided they  clarify  and
 present items of importance to applications.  Clear,  not overly  formal,
 writing is essential.

 All articles will be carefully peer reviewed. Authors whose articles  are
 accepted on technical grounds will work with the magazine's staff editors
 to arrive at a final article that is clear, straightforward, and valuable
 to the user community.

 Full publication guidelines are available at
 http://computer.org/pubs/expert/edguide.htm, or from the  managing editor
 at [EMAIL PROTECTED]