Posts on Jamie Collinson

Solving Knights and Knaves with Z3

Mon, 17 Jun 2019 00:00:00 +0000

Historical note: playing with Z3 paid off when I later used it to implement optimal fertiliser selection in Virtual Agronomist

There’s a type of logic puzzle called Knights and Knaves, in which we have a set of people who will either always tell the truth - a Knight - or always lie - a Knave.

Suppose we have two people, A and B, with A claiming “We are both Knaves”. What can we deduce? A must be a Knave, since if he were a Knight he could not claim to be a Knave. Since Knaves always lie A and B cannot both be Knaves, and so B must be a Knight.

Emacs Config

Sun, 11 Mar 2018 14:33:18 +0000

This is my emacs configuration. After many years with vim then a year with spacemacs & prelude, I came to the realisation that I needed to construct my own to really get it¹.

After a few aborted attempts to split the config into separate files, I settled on the single file literate approach via Sacha Chua.

Documenting this is mostly for my benefit, but I hope others might find it useful constucting their own. The live version is on GitHub, with this version updated periodically.

A guide to disassembling the Ricoh GR for sensor cleaning

Mon, 30 May 2016 00:00:00 +0000

Updated: 2020-06-22 to add GR2 details sent by a kind reader

The Ricoh GR is an excellent camera, which has managed to displace all my former dalliances due to it’s size, near-perfect ergonomics and incredible performance. But it does have a design flaw. Dust gets sucked into the lens assembly far too easily.

On a recent trip I found lots of annoying dust spots. This is easy to fix, but tedious¹.

A mathematician, a physicist and an engineer...

Sat, 28 May 2016 00:00:00 +0000

A mathematician, a physicist and an engineer are away from home at a conference¹.

The engineer wakes up in the night to find his bed is on fire. He grabs the fire extinguisher, points it at the fire and sprays until the fire is safely extinguished. He goes back to sleep content he has solved the problem.

The physicist wakes up in the middle of the night to find his bed is also on fire. He spots the fire extinguisher, takes his notepad and pencil, and after a quick calculation puts the fire out with one well timed burst. He returns to sleep pleased with his elegant solution.