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From: news@cs.yale.edu (Usenet News)
Newsgroups: comp.lang.eiffel
Subject: Quicksort?  (was Re: Coping with failure)
Message-ID: <17412@cs.yale.edu>
Date: 1 Mar 90 00:42:34 GMT
References: <25EB6B0D.2249@maccs.dcss.mcmaster.ca> <1880@clyde.concordia.ca>
Reply-To: jellinghaus-robert@yale.UUCP
Organization: Yale University Computer Science Dept, New Haven CT  06520-2158
Lines: 27

In article <1880@clyde.concordia.ca> marcap@hercule.CS.Concordia.CA (PAWLOWSKY marc) writes:
>consuming.  For example I just wrote a class to perform quick_sort.  The
>properly check that the procedure has worked it is necessay to check
>that the cardinality is still the same, all objects that entered the array
>exit the array, the output is sorted.  When an object is "put" into a
>structure it should also be checked that the object is in the structure.

I would expect that the postconditions for the standard Eiffel library would
include assertions to perform the checking you describe (such assertions do
seem like a good idea), but upon examination I see they don't.  I wonder
why not?  They wouldn't be compiled into the libraries as distributed, and
they would provide good examples of correct assertion writing.

On another note, would it be possible for you to post your quicksort class?
At what level of the library does it operate?  I for one hope that such 
classes become more common.  I like the Eiffel implementations of standard
computer science data structures, but classes implementing standard CS
_algorithms_ seem a bit further behind.  They could be every bit as helpful,
though....

>Marc Pawlowsky    Grad Student   Concodia University


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