Return-Path: 
 <dev-return-131888-apmail-commons-dev-archive=commons.apache.org@commons.apache.org>
X-Original-To: apmail-commons-dev-archive@www.apache.org
Delivered-To: apmail-commons-dev-archive@www.apache.org
Received: from mail.apache.org (hermes.apache.org [140.211.11.3])
	by minotaur.apache.org (Postfix) with SMTP id D58467428
	for <apmail-commons-dev-archive@www.apache.org>;
 Thu, 15 Dec 2011 13:20:50 +0000 (UTC)
Received: (qmail 19832 invoked by uid 500); 15 Dec 2011 13:20:50 -0000
Delivered-To: apmail-commons-dev-archive@commons.apache.org
Received: (qmail 19726 invoked by uid 500); 15 Dec 2011 13:20:50 -0000
Mailing-List: contact dev-help@commons.apache.org; run by ezmlm
Precedence: bulk
List-Help: <mailto:dev-help@commons.apache.org>
List-Unsubscribe: <mailto:dev-unsubscribe@commons.apache.org>
List-Post: <mailto:dev@commons.apache.org>
List-Id: <dev.commons.apache.org>
Reply-To: "Commons Developers List" <dev@commons.apache.org>
Delivered-To: mailing list dev@commons.apache.org
Received: (qmail 19718 invoked by uid 99); 15 Dec 2011 13:20:50 -0000
Received: from athena.apache.org (HELO athena.apache.org) (140.211.11.136)
    by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 15 Dec 2011 13:20:50 +0000
X-ASF-Spam-Status: No, hits=2.2 required=5.0
	tests=HTML_MESSAGE,RCVD_IN_DNSWL_LOW,SPF_NEUTRAL
X-Spam-Check-By: apache.org
Received-SPF: neutral (athena.apache.org: local policy)
Received: from [209.85.212.43] (HELO mail-vw0-f43.google.com) (209.85.212.43)
    by apache.org (qpsmtpd/0.29) with ESMTP; Thu, 15 Dec 2011 13:20:42 +0000
Received: by vbbfq11 with SMTP id fq11so4879973vbb.30
        for <dev@commons.apache.org>; Thu, 15 Dec 2011 05:20:20 -0800 (PST)
MIME-Version: 1.0
Received: by 10.52.20.209 with SMTP id p17mr3057293vde.60.1323955220598; Thu,
 15 Dec 2011 05:20:20 -0800 (PST)
Sender: jcarman@carmanconsulting.com
Received: by 10.220.2.138 with HTTP; Thu, 15 Dec 2011 05:20:20 -0800 (PST)
Received: by 10.220.2.138 with HTTP; Thu, 15 Dec 2011 05:20:20 -0800 (PST)
In-Reply-To: 
 <CAHQS_exHiJjMbnsxeKpqfPCR11WCfgh+QyZhecJ95RhfpV9kVw@mail.gmail.com>
References: <4EDC0593.5070200@dia.uniroma3.it>
	<4EE545AE.1020906@dia.uniroma3.it>
	<CALznzY6GRWLFthfTpk=4hij3q76p+-a9E5U1FDBdGiBJX6kUtQ@mail.gmail.com>
	<CALznzY6VGNUe3ZP6aCuHzE_qNNE1LPj+hhiP3hGMXw7jYjXnRw@mail.gmail.com>
	<4EE61054.3090906@dia.uniroma3.it>
	<CALznzY7py=Df9E=-LDc+OwTmqL17wpwkrgzXuids94mpNCo5gw@mail.gmail.com>
	<CAAqLGLOXfSKq3NS8VFE9Zv=XizpRr2OjUx2mEV303FHvkPxcKA@mail.gmail.com>
	<4EE78CEC.3090403@dia.uniroma3.it>
	<CALznzY6Vj-4fGsHeoBQstwRWQ6-Tbnk9uUskEo9EBE7wj3WwEw@mail.gmail.com>
	<4EE895F4.9050802@dia.uniroma3.it>
	<CALznzY7oh4x5toZqpZSD5t0HyGXeBujy5-SSaxURcU+UWj5ApA@mail.gmail.com>
	<CAHQS_exHiJjMbnsxeKpqfPCR11WCfgh+QyZhecJ95RhfpV9kVw@mail.gmail.com>
Date: Thu, 15 Dec 2011 08:20:20 -0500
X-Google-Sender-Auth: rFwRMEHluz62LBaAdtphbtDjtZ0
Message-ID: 
 <CALznzY7Ri5q0=fa1qYbCYPN=gyG1yW0vt05G7zwfiFt5CyJryA@mail.gmail.com>
Subject: Re: [Graph] On graph weight type(s)
From: James Carman <james@carmanconsulting.com>
To: Commons Developers List <dev@commons.apache.org>
Content-Type: multipart/alternative; boundary=20cf307d05cc9f513f04b421585c

--20cf307d05cc9f513f04b421585c
Content-Type: text/plain; charset=ISO-8859-1

We may be modeling the domain properly with all of this terminology, but is
this going to be understandable to the common user?
On Dec 15, 2011 7:38 AM, "Matthew Pocock" <turingatemyhamster@gmail.com>
wrote:

> Hi,
>
> On 15 December 2011 11:35, James Carman <james@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: turingatemyhamster@gmail.com
> gchat: turingatemyhamster@gmail.com
> msn: matthew_pocock@yahoo.co.uk
> irc.freenode.net: drdozer
> skype: matthew.pocock
> tel: (0191) 2566550
> mob: +447535664143
>

--20cf307d05cc9f513f04b421585c--