Re: [gentoo-dev] portage-ng concurse entry Was: Updated Portage project page

[George Shapovalov]

Oops, sorry, looks like I mixed replies of two different people on different 
lists and coupled my answer together in gentoo-portage-dev.
I am correcting this now, but first I'll repeat the same disclaimer which I 
think I need to do more noticable in the write-up.

As I stated in the writeup, the "design" discussed is a simplistic model only 
relevant for the prototype which goal was basically to demonstrate 
capabilities of a particular language and nothing else. 
Thus note, all the comments below concern this hypothetical design I used in 
language demonstration, but that will probably be rethought for the real 
design (and there was just a tiny bit more on that on gentoo-portage-dev 
list).

Therefore
> I don't see any reasoning about versions, virtuals, constraints, slots,
> updates, upgrades, downgrades, ...
just because there is none.

Now, the next comment is the reason I did this reply, please do not take 
seriously the rest :).

On Friday 05 December 2003 09:46, Pieter Van den Abeele wrote:
> On 05 Dec 2003, at 10:58, George Shapovalov wrote:
> > To reiterate them shortly, Prolog is a really esoteric language and I
> > am not
> > sure we will be able to find enough people to feel comfortable about
> > having
> > the very core of portage-ng implemented in it. Also there might be
> > issues of
> > portability and efficiency..
>
> My biggest concern when reading your small paper is that you chose a
> deterministic approach to this problem, while in fact the problem is
> non-determinisitic.
Could you please elaborate? I am afraid we are thinking about slightly 
different things here.

I stay by my thought that any important to the system tool should be dumb. If 
there is any uncertainty it should stop and ask, unless it was designed for a 
very specific situation, where it can be trusted to make the choice. Package 
maintaince is not such area - IMHO every user that has identical 
configuration should get identical results (to the extent possible. So here 
we are talking requirements Daniel ;)). Otherwise we are facing a disasterous 
consequencies with many people complaining and us being unable to reproduce 
anything reliably.


>Also, your code (which is about 1000 lines long)
> does -only- a simple dfs and topological ordering, while I can do the
> same in about 10 lines in prolog and have backtracking for free. I
This is anecdotal.

The *traversal* code  is completely 
localized in bc-graphs-directed-bfs_traverse.adb and is about the same 10 
lines :) and is completely generic. 
The rest of 990 lines deal with such mundane tasks as reading the (possibly 
misformed) ebuilds and dealing with user (inluding minimalistic help). 


> I don't want to start a flame war about programming languages. That
> would be totally useless because the nice thing about programming
> languages is that they are all somewhat equivalent but some more
> expressive than the other for a given problem.
>
> For my thesis and apprenticeship at the Theoretical Computer science
> laboratory at the free university of Brussels (tinf.vub.ac.be), I have
> been looking into these issues. The techique we have developed for
> reasoning about large software configurations such as a
> meta-distribution will be presented on a Gentoo meeting in the future,
> and can be implemented in any language you prefer. I will have a fully
> functional prototype in prolog, because that language offers some
> benefits, but the idea itself can be implemented in any other language
> such as Ada or friends.
Ok, thanks, there wasn't that much verbal info other than "there is a 
prototype inplementation in prolog", but fortunately Daniel yesterday put the 
things into a proper perspective :). In any case my goal wasn't to push for a 
particular language either but to increase "awareness" :), and I now 
completely stay by the proper procedure. 

George



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