On the day after the tournament, we had a coach tour of Vancouver. The first stop was the Steam Clock. This is an upright weight-driven clock, with alarms powered by steam from the district heating system. It is apparently very important. Next stop was Granville Island, opposite Vancouver Island. This is mostly a former industrialContinue reading “WAGC Day 5 – tour of Vancouver”
Author Archives: alistairjwall
WAGC 2025 day 4
In the morning I lost to David He 5 dan of Australia. I did not attack strongly enough, and ended up 15 points behind. In the afternoon I beat Marc Stoehr 2 dan of Sweden. Both of us missed the big move around 31 for a long time, but I got there first. After IContinue reading “WAGC 2025 day 4”
WAGC 2025 Day 3
In the morning I lost to Andrius Petrauskas 4 dan of Lithuania. I tried to attack a group that I thought was heavy, but played a slow move and fell behind. There was an official recorder, so I should be able to get the record later – it may be on Pandanet. Update: On theContinue reading “WAGC 2025 Day 3”
WAGC 2025 Day 2
In the morning, I lasted half an hour against Ioan-Elian Grigoriu 6dan of Romania, and in the afternoon Mario Roberto Gómez Flores 5kyu of Guatamala did the same against me. The tournament site is https://leago.gg/event/wagc2025
WAGC 2025 Day 1
There are four hotels called Vancouver Airport Hotel on the same stretch of road, and the tournament venue Executive Airport Hotel is the last to appear when I zoom in on Google maps. That is why yesterday I walked in the opposite direction to what I intended. This morning, I walked to Minoru Park, whichContinue reading “WAGC 2025 Day 1”
WAGC2025 – Welcome
The first day started with a pair go tournament where competitors were paired with local players. The organisation was a bit chaotic; I was standing in the wrong place and did not get paired. I took the opportunity to go for a walk. Vancouver is not designed for walking – everything is organised to beContinue reading “WAGC2025 – Welcome”
World Amateur Go Championship 2025
After 30 years of coming last in the British Championship, I have accumulated enough points to represent the UK in WAGC 2025 in Vancouver (May 16-23). I had a sleepless night when Canadian Airways’ web check-in could not find my eTA (electronic visa), but in person at the airport, everything worked smoothly. There are aboutContinue reading “World Amateur Go Championship 2025”
Advent of Code 2021 Day 16
https://adventofcode.com/2021/day/16 This is the hardest of the problems I have managed to solve. Some of the issues were: On the good side, Attoparsec can handle the non-context-free aspects (eg the functions packets0 and packets1). Almost every line of the solution can be linked back to the puzzle’s requirements – there is very little visible plumbing.Continue reading “Advent of Code 2021 Day 16”
Attribute Grammars with Monads
Attribute grammars evaluate recursive data structures where inherited attributes are passed from the root to the leaves, and synthesised attributes are calculated in the leaves and passed back to the root. In “Beginning Haskell” pp343-4 (Apress ISBN 978-1-4302-6250-3), Alejandro Serrano Mena briefly discusses implementing attribute grammars using the Reader and Writer monads. He does notContinue reading “Attribute Grammars with Monads”
Observations of Kirch’s comet 1680-81
The observations Newton used to calculate the orbit of Kirch’s comet can be found in the tables in http://www.newtonproject.ox.ac.uk/view/texts/diplomatic/NATP00301 page 491. Observations up to 5 February are by Flamsteed; later observations are by Newton. Different versions of these tables exist. This version is sufficient to demonstrate the calculation. I have not found the Newton Project’sContinue reading “Observations of Kirch’s comet 1680-81”
Great Wall 