Aptitude package installation order (Squeeze)

[Nick <nmb3000@gmail.com>]

Hello,

A pretty simple question: Does the order packages to install are
listed on the aptitude command line matter?  This is on an updated but
very bare-bones Squeeze installation (pretty much nothing installed
but the base system).

I've always thought it didn't and that dependency resolution wouldn't
care about the order you happen to list the packages in.  Also, I've
looked around and haven't seen any reason to think that order matters.

However, while setting up a test system this week I ran "aptitude
install ..." with a dozen or so packages listed in no particular order
just to make sure I remembered the package names correctly.  Aptitude
had no problems and prompted me to install everything.  I said "No" to
the installation prompt and then saved the package list to a text file
and sorted it.

Since my package list was correct and working, I ran aptitude again
and told it to install that (now sorted) list of packages.  This time
aptitude threw up an unmet dependencies warning.  I thought I'd
screwed up my packages, but checking showed the same packages, just in
a different order.  Pruning the list, I've got it down to these two
causing the problem:

This command has no problems: aptitude install php5-gd imagemagick

This command complains about conflicts between libgd2-xpm and
libgd2-noxpm: aptitude install imagemagick php5-gd

Can anyone help explain this behavior?

Thanks,

Nick