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Message-ID: <4158B0F5.C19503F@dessent.net>
Date: Mon, 27 Sep 2004 17:31:49 -0700
From: Brian Dessent <brian AT dessent DOT net>
Organization: My own little world...
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To: cygwin AT cygwin DOT com
Subject: Re: Is setup.exe _supposed_ to delete the cygwin dll before attempting to run shell scripts?
References: <NUTMEG1NFh5TAAl4sAt0000010c AT NUTMEG DOT CAM DOT ARTIMI DOT COM>
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Dave Korn wrote:

> > Oh, did I forget to say the graph must be a DAG before starting?  :)
> > Anyway, there are heuristics that could be used to find the best
> > "feedback set" of edges for which removal would result in an acyclic
> > graph.  e.g. the one described at
> > <http://www2.toki.or.id/book/AlgDesignManual/BOOK/BOOK4/NODE182.HTM>
> 
>   Deleting edges from a graph won't actually make a package that depends on
> another operate successfully without that other package present!  OTOH what
> I think might work would be to identify loops in the full dependency graph
> and treat them as single packages that must be installed or uninstalled
> together - effectively encapsulating the loop inside a single node and
> thereby reducing the graph to a DAG.

I was really only suggesting it as a way to order installation and
uninstallation, not as a general dependency mechanism.  If you have a
circular dependency there's no way to resolve which preremove /
postinstall should be run first (unless you launch them both in the
background :) so the act of finding the minimal number of edges
necessary to remove the cycles shouldn't cause too much issue.

Brian

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