My old webpage is here.

april 24, 2015 04:02pm

Combinatorial baby toy

Unsuspecting, I picked this classic baby toy up at a local charity sale. As it turned out, it harbours a little combinatorial challenge that I never suspected! The toy is a set of five stacking cubes with a different face on each face. Save for size, the cubes are all the identical; flower, hexagon, square, triangle, circle, and the open face.


As I was playing with it I thought, "Can I stack the cubes such that no two shapes coincide?". Fun!

This is the same as asking if you can orient 5 6-sided (axis-aligned) dice so that no two dice show the same number on the same side.

Is there more than one way to do it? Can it be done with 6 stacking cubes?


november 14, 2014 01:13pm

A nice BibDesk template for listing publications in HTML

For some reason the templates in BibDesk never do quite what I want, and I end up spending hours remaking templates. That is what I did today, in order to list a few of my publications on my homepage in HTML. For example, the ones below (click here for the list on my academic homepage):

Alejandro Erickson and Frank RuskeyGenerating Tatami Coverings EfficientlyProceedings of the International Conference Génération Aléatoire de Structures Combinatoires (GASCom) 2014, Bertinoro, Italy, 2014.

Alejandro EricksonMonomino-Domino Tatami CoveringsUniversity of Victoria, 2013.

The BibDesk template is set up so that I can select the items I want to export, right click them and choose "copy using Template>Default HTML Template". It has special protocols for article, inproceedings, phdthesis, mastersthesis, and unpublished, and treats everything else like an article. The only thing I seem to need to do manually is html accents.

If you have not installed BibDesk templates before it can be a bit tricky to set up a multi-file template like this. Fortunately, there are pretty good instructions here, but I'll just go through what you can do with the files attached to the post anyway. Begin by putting the files attached here into your templates folder, usually at "~/Library/Application Support/Bibdesk/Templates".

Open BibDesk>Preferences to the "Templates" tab. Without expanding any of the items, press the "+" button, and follow the instructions on screen to add the file "htmlListTemplate.html", and set its role to "Main page". Press the "+" button again, and add the file "htmlExportStyleSheet.css" (you should find this in your templates folder), and set its role to "Accessory File". Do this for htmlListArticle.html, htmlListInproceedings.html, htmlListPhdthesis.html, and htmlListUnpublished.html, setting their roles as required. Add the article and phdthesis templates again, setting new roles to default and mastersthesis.

When finished, you'll have an item in your templates list like this:

Your bibdesk templates preference screen should look like this.

Here are the files:


As an aside, and a reminder to myself, I generated the list by using the command:
$ls -1 | sed 's/\(.*\)/<a href="im\/bibdesk_html\/\1" download="\1">\1<\/a><br \/>/g'

november 11, 2014 06:59am

Psychotic Storm Collaboration with Patrick Montgomery

I have been doing art for myself, my friends, and whoever wishes to peer into my life through the Inter-window for a few years now, but one thing I want more of is artistic collaboration. It seems to me that there is not better way to get to know another artist, or strengthen a friendship than doing something creative together.

Musicians get this (if you'll allow the generalisation). Many other artists do too, but the vast majority of us are working alone. I am looking for collaborative experiences, and as a first step, I'm proud to present the following collaboration between myself and my childhood friend Patrick Montgomery.

"Psychotic Storm" began with a nighttime thunderstorm over Lake Michigan, where I laid my film camera on the promenade in Chicago for a long exposure. Patrick's textures and "psychotic" colour palette emphasise the uneasy tension between the typically serene sailboats resting on calm waters, and the tumultuous sky above them.

Original image:

Summer Storm over Marina, 35mm film

Reworked image: Psychotic Storm

Psychotic Storm

november 05, 2014 10:50am

Getting Serious with Photography

Having grown up around SLR cameras, I have always had an appreciation for the superior image quality that a "proper" camera is capable of. I have owned severalof them, and I am quite familiar with the technical aspects of exposure and depth of field. A tipping point occured, however, when I got my hands on a Sony alpha A7 this year. I went on to read The Landscape Workshop by Ross Hoddinott and Mark Bauer, and dove into capturing the rural landscape around my home in the North East of England.

Here is one of my "keepers":

Rusty, Windswept Puddle

Here is another one:
"So then he texts me back..."

october 23, 2014 10:55am

Exchange a Canadian Driving Licence for UK Category B Licence No Restrictions

I am a Canadian citizen, resident in England, and I have recently learnt some things while getting a UK Driving Licence. First and foremost, the following website is a gold mine:


Read that whole webpage.

There were a few details missing, however, as regards insurance and provisional entitlements, and I will fill those in here. As you will learn at gregwtravels, you can exchange you Canadian licence for a Category B restricted to Automatic (this is code 78).

The first thing I can confirm is that you do not need to have your photos signed if you send in your Canadian passport (i.e. you do not need a UK passport). At the time of this writing gregwtravels says "I take that to mean that an up-to-date Canadian passport is identity enough.". Yes, it was enough for me, and if you read the instructions that come with the D1 form, you can reassure yourself of this.

To fully understand the codes on your licence, you should refer to the following document:

Information on driving licences INS57P

The INS57P is the pamphlet code at the time of this writing, in case the link goes dead. You should be able to find the same pamphlet by searching for INS57P driving licences.

INS57P also tells you that you can find your provisional entitlements on your "Counterpart Driving Licence", which is the paper document that came in the mail with your photocard. This is where you can verify gregwtravels' claim that you can drive a Category B (without restriction) as a provisional driver. I have checked with a human at the DVLA, to confirm that you must be accompanied by a fully licenced (IN THE UK) Category B driver for this to work (i.e. not your Canadian partner who is still on their international driver's licence).

The next question for me was "How do I insure myself to take the test in my own car?". You need insurance that covers you as a provisional driver, plus the car must have its own "full" insurance. This cost me 85 GBP from, but at the time of this writing, I have not confirmed that my setup works. That is, I think I am covered because:

There are three pitfalls, however, that might apply (which I will clear up when I talk to a human at provisionalmarmalade); perhaps owning the main insurance voids the provisional insurance; and, perhaps the insurance is not valid during the test (this is apparently the policy of ecar insurance!); perhaps the fully UK Category B licenced driver needs to be listed on the full insurance of the car.

Update: The following quotes from my insurance terms and conditions (and schedule) clear up the above doubts, more or less confirming that I am covered during my test, and that I can drive when supervised by a driver meeting the conditions mentioned:

"Driver to be accompanied – (Name)
We will not provide cover while your vehicle is being driven by, or is in the charge of, the person(s) named above unless that person is accompanied at all times. The accompanying person must be 25 or over and must hold a current full UK driving licence which has been issued for at least three years. These restrictions do not apply if the accompanying person is a Department of Transport approved driving instructor or examiner."


"Emergency and 'Get Your Vehicle Home' Cover While you are receiving driving tuition or undergoing an official DSA practical driving test, we will extend the cover if it is necessary because of an emergency or other exceptional circumstances to allow your accompanying full UK licence holder (who must be over 25 years of age and must have held such licence for a minimum of 3 years or who must be a qualified DSA Examiner) to drive the insured vehicle in order to complete the journey."

The full terms and conditions are available on their website here, and I have posted a copy here.

To book the test itself, I went to the website recommended on gregwtravels called Book your driving test. I called the DVSA booking support number, and chose options 02, and then option 6 (other). (I was tempted by option 2, DVLA enquiry at phone 03007906801, but I do not think this is a correct option.) The test cost me 62 GBP.

Finally, I did book one driving lesson, which cost 44 GBP.