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We have the game ‘Guess Who’, which comes with a selection of sheets to play variants of the original game. In a flash of comedy inspiration, my eldest, Marlowe, and I thought it would be excellent if there was a game called ‘Guess Poo‘. In Guess Poo, instead of trying to identify faces, you have to identify faeces. We therefore set about designing drop-in sheets for our game. (‘Guess Who’ is probably a trademark of Hasbro or Milton Bradley, and I would be very surprised indeed if either of them endorsed this post.) Choice of characteristics In the original, the faces have different values for various characteristics, such as hair colour, whether they wear glasses, gender, and so on. It

In logic, we talk about propositions, giving them names, say p or q. For example, p might be the proposition ‘it is raining’, and q the proposition ‘I will get wet’. Then to represent the proposition ‘if it is raining then I will get wet’, we can say ‘p IMPLIES q‘, which is often written with a double-arrow: p ⇒ q. In ASCII, this can be approximated by ‘p => q‘. In full, this operator has the following truth table: p q p => q T T T T F F F T T F F T (This appears slightly strange, but the only way we can disprove the claim ‘p implies q‘ is if p happens but q doesn’t.) In many programming languages,

I saw an interesting number-based game at the 2015 Young Scientist show. This post derives, using brute force, a winning strategy for the game and implements it as a ‘human vs computer’ setting.

A couple of recent posts here — An oscillator from a jam-jar lid The value of a second opinion — required some post-specific Javascript and CSS styling. It took me a little while to figure out how to achieve this, given my limited exposure to PHP in general and WordPress programming in particular. This is how I went about it; there may well be better ways. Start writing post At this point your draft is assigned a post-ID. This is the value at the end of the post’s URL. For example, this post has URL https://redfrontdoor.org/blog/?p=970 and its post-ID is 970. Write post-specific Javascript Make a self-contained Javascript file, wrapping the logic in jQuery(document).ready(function($) { // [… code goes here

You feel ill and go to a doctor. She does a test and says ‘you have a 70% chance of having the Lurgy’. You go to a different doctor, who does a different test, but also says ‘you have a 70% chance of having the Lurgy’. Given these two test results, what are your chances of having the Lurgy?

A one-character documentation fix for ‘git’.

Update 2022-07-12: I recently received an email from Pablo Vidal (@this_may_be_it), who had success getting with a similar project, using a MiniDisc player — see the end of this post for details. The idea for this project came from a few different places: Curiosity about how cable modems actually transmit ones and zeros along the coax cable. This led to some reading about the various modulation methods used. Code I’d written to read the data on cassette tapes containing files from the Dragon 32 computer of my youth. (Including this one.) The modulation here is fairly simple, being one cycle of a certain tone for a ‘0’ and one cycle of a different tone for a ‘1’. Some fairly superficial reading

My 7-year-old daughter and I built a robot which plays the memory game ‘Simon’. Servos use string to pull ‘fingers’ made out of Lego, pressing the game’s buttons. Phototransistors sense which lights are flashing, with an Arduino controlling everything. It successfully plays a complete game of Simon!

RTE recently carried a news piece announcing the release of a large volume of historical digital images by the National Library of Ireland. One detail in the piece caught my eye: it quoted the library’s Digitisation Programme Manager Sara Smyth as saying Since 2010, we have overhauled our digitisation workflows and put in place key technical infrastructures. We achieved this with limited full time technical resources and a very restricted budget by collaborating on international open source projects. (emphasis added). This sounded like a great thing. I wondered what projects these were, so emailed Ms Smyth. She and a colleague wrote back, kindly supplying plenty of detail, which this post reports. Engagement with open source projects generally Perhaps unsurprisingly, Systems

© Trustees of the British Museum[source page] On a recent visit to the British Museum in London, I was interested to see a very curious escapement mechanism in one of the clocks, a creation of Thomas Tompion in the 1670s. I am certainly no expert on clocks, but I had never seen an escapement where the pendulum swings across the plane of the gear wheels. Frustratingly, the actual mechanism was very small, and in the middle of quite a large glass case, so I could not see it well enough to work out what it was doing. I spent a bit of time thinking about it, and came up with an idea for what might be happening, but now the