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000049_icon-group-sender _Wed Feb 26 17:15:42 1997.msg
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Received: by cheltenham.cs.arizona.edu; Thu, 27 Feb 1997 09:03:41 MST
To: icon-group@cs.arizona.edu
Date: 26 Feb 1997 17:15:42 GMT
From: espie@fregate.ens.fr (Marc Espie)
Message-Id: <5f1r3u$b7l@nef.ens.fr>
Organization: Ecole Normale Superieure, Paris
Sender: icon-group-request@cs.arizona.edu
References: <331437DE.41C67EA6@solstice.digicomp.com>
Subject: Re: Icon and two-dimensional matching
Errors-To: icon-group-errors@cs.arizona.edu
Status: RO
Content-Length: 2405
In article <331437DE.41C67EA6@solstice.digicomp.com>,
Jan Galkowski <jan@solstice.digicomp.com> wrote:
[SMALLER reply though]
>[LONG post warning!]
>Now, I don't in any way want to depreciate or criticize the use or
>power of Icon in traditional programming. Indeed, seeing how
>traditional problems can be addressed by new methods and
>expressive styles is crucial to developing programming itself.
>While the conceptual algorithm for expression may be about the
>same, the means used to realize it with the "generate and test" mindset
>available in Icon can be dramatically different than in, say, Ada.
>Moreover, there are some algorithms which, because of the
>availability of Icon's tables, may now be usable and practical
>because the effort to use these elements is negligible compared to,
>again say, Ada since their one might need to implement the
>elements. It is important to continuously reconsider putting
>new wines in "old bottles" if the depth of our collective craft
>is to be maintained.
Icon tables and sets are indeed a very powerful mechanism. However,
they sometimes suffer from their generality. The current implementation
uses hash functions that assume a rather smooth average distribution
of the data.
I've been using Icon a lot for combinatorial computations involving
words, lattices and graphs, where Icon excells thanks to its
generators, and high-level operations on sets.
However, I've also ran into some spectacular failures. You see, the
sets of words I study are NOT average. Indeed, I am trying to find
some non obvious correlations between those... and the hashing functions...
well, I've got cases where everything ended up in one or two buckets,
or rather larger sets where the hashing process failed due to the
sheer size of the data.
I would rather like to be able to specify MORE things about my sets
(average size, distribution of data, other hashing functions) than
is possible with the current implementation.
Right now, I have to reinvent the wheel, and reimplement somehow my
own sets without all the clarity Icon procures to us.
(I'll admit that Icon sets and tables works in more than 95% of
the cases I've thrown at it)
--
[nosave]<http://www.eleves.ens.fr:8080/home/espie/index.html>
microsoft network is EXPLICITLY forbidden to redistribute this message.
`Seiza no matataki kazoe, uranau koi no yuku e.'
Marc Espie (Marc.Espie@ens.fr)