From esigra at gmail.com  Tue Nov  3 13:04:09 2009
From: esigra at gmail.com (Erik)
Date: Tue, 03 Nov 2009 13:04:09 +0100
Subject: [Python-logic] Is this the tool to solve this little problem?
Message-ID: <4AF01C39.20500@gmail.com>

I was looking for a simple tool to solve little problems. For example I
would like to give the following input:

k * 160 + m * 30 + n * 15 = 700
k + m + n ? 6

Then I would like to get the following output:
k = 4, m = 2, n = 0


Here is a textual description of the problem: An item of meat costs 160.
An item of fish costs 30. An item of milk costs 15. Someone spent 700
and bought at most 6 items. What did he buy?

If the second line of input would be omitted (at most 6 items), the
output should include more solutions, such as:
k = 4, m = 0, n = 4


I searched for a program to do this kind of calculations. I would prefer
something that is as easy to use as for example the factor program of
GNU coreutils. The closest thing that I stumbled upon was
logilab-constraint. But I have not figured out if it is the right tool.
I do not even know Python. (Just wrote 1 little script in it and
modified some others when I had to.)


I am not sure if this example is an assingnment problem, or if it should
rather be classified as an integer programming problem or constraint
satisfaction problem.

From nicolas.chauvat at logilab.fr  Tue Nov  3 13:25:01 2009
From: nicolas.chauvat at logilab.fr (Nicolas Chauvat)
Date: Tue, 3 Nov 2009 13:25:01 +0100
Subject: [Python-logic] Is this the tool to solve this little problem?
In-Reply-To: <4AF01C39.20500@gmail.com>
References: <4AF01C39.20500@gmail.com>
Message-ID: <20091103122501.GA17917@volans.logilab.fr>

Hello,

On Tue, Nov 03, 2009 at 01:04:09PM +0100, Erik wrote:
> I was looking for a simple tool to solve little problems. For example I
> would like to give the following input:
> 
> k * 160 + m * 30 + n * 15 = 700
> k + m + n ? 6
> 
> Then I would like to get the following output:
> k = 4, m = 2, n = 0
> 
> ...
> 
> I am not sure if this example is an assingnment problem, or if it should
> rather be classified as an integer programming problem or constraint
> satisfaction problem.

To solve that kind of problem, you can use either

http://www.logilab.org/project/logilab-constraint/
http://code.google.com/p/pulp-or/

Look at the examples in both packages and you will find what you are
looking for.

http://hg.logilab.org/logilab/constraint/file/3d51e72774e6/examples
http://code.google.com/p/pulp-or/wiki/OptimisationWithPuLP

-- 
Nicolas Chauvat

logilab.fr - services en informatique scientifique et gestion de connaissances