Hi,
On 15/12/2011 14:20, James Carman wrote:
We may be modeling the domain properly with all of this terminology, but is
this going to be understandable to the common user?
I highly appreciated the last contributions (thanks guys!) but I also
agree on this point, so let's start from the end.
I think that, no matter what underlying structure we come up with, the
user should be able to specify e.g. a weighted edge with something like
public class MyEdge implements Edge, Weighted<Double> { ... }
and be able to immediately use it as an input for all the algorithms,
without extra steps required. So the average user is happy, while "graph
geeks" can dig into advanced capabilities and forge their personalized
weights :)
I hope we all agree on this as a first step. Complexity comes after.
I'll take my time as well to re-think.
Claudio
On Dec 15, 2011 7:38 AM, "Matthew Pocock"<turingatemyhams...@gmail.com>
wrote:
Hi,
On 15 December 2011 11:35, James Carman<ja...@carmanconsulting.com>
wrote:
public interface BinaryOperation<T>
{
public T execute(T operand1, T operand2);
}
Perhaps we can come up with an interface that combines the two
aspects. I'm trying to think of mathematically what that would be
called. By the way, what do you need to know "HasZero"? A sum
operation has to have a "zero", doesn't it?
The mathematical hierarchy goes: semigroup -> monoid.
http://en.wikipedia.org/wiki/Semigroup
http://en.wikipedia.org/wiki/Monoid
You don't need a full group here as you are only interested in a single
operation, not a pair of interacting operations. There are several
JVM-hosted libraries that model this hierarchy to a greater or lesser
degree. scalaz uses:
trait Semigroup[S] {
def append(s1: S
<
http://scalaz.googlecode.com/svn/continuous/latest/browse.sxr/scalaz/Semigroup.scala.html#22357
,
s2: => S): S<
http://scalaz.googlecode.com/svn/continuous/latest/browse.sxr/scalaz/Semigroup.scala.html#22357
}
trait Zero[Z] {
val zero: Z<
http://scalaz.googlecode.com/svn/continuous/latest/browse.sxr/scalaz/Zero.scala.html#22160
}
trait Monoid[M] extends Zero
<
http://scalaz.googlecode.com/svn/continuous/latest/browse.sxr/scalaz/Zero.scala.html#17945
[M]
with Semigroup<
http://scalaz.googlecode.com/svn/continuous/latest/browse.sxr/scalaz/Semigroup.scala.html#15476
[M]
http://scalaz.googlecode.com/svn/continuous/latest/browse.sxr/scalaz/Semigroup.scala.html
http://scalaz.googlecode.com/svn/continuous/latest/browse.sxr/scalaz/Zero.scala.html
http://scalaz.googlecode.com/svn/continuous/latest/browse.sxr/scalaz/Monoid.scala.html
If you're not used to reading scala, here's the essentially equivalent
definitions in Java:
public interface Semigroup<S> {
public S append(S s1, S s2);
}
public interface Zero<Z> {
public Z zero();
}
public interface Monoid<M> extends
Zero<
http://scalaz.googlecode.com/svn/continuous/latest/browse.sxr/scalaz/Zero.scala.html#17945
<M>,
Semigroup<
http://scalaz.googlecode.com/svn/continuous/latest/browse.sxr/scalaz/Semigroup.scala.html#15476
<M>
So, given that you have Ordering<O> already (or is that Comparator<C>?),
I'd say that Weight is defined as:
// insert comments here about the consistency of append and compare
public interface Weight<W> extends Monoid<W>, Ordered<W>
Of course, a sensible default implementation of Weight would delegate to
Monoid and Ordered instances and you can then pray to the gods of hotspot
to inline this all away.
public<W> Weight<W> weight(Monoid<W> m, Ordered<W> o) {
new Weight<W>() {
public W zero() { return m.zero(); }
...
}
}
Matthew
--
Dr Matthew Pocock
Integrative Bioinformatics Group, School of Computing Science, Newcastle
University
mailto: turingatemyhams...@gmail.com
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--
Claudio Squarcella
PhD student at Roma Tre University
E-mail address: squar...@dia.uniroma3.it
Phone: +39-06-57333215
Fax: +39-06-57333612
http://www.dia.uniroma3.it/~squarcel
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