2026-10-31T17:23:33Z https://njump.me Jeremy Gibbons https://njump.me/npub1349jhlr98dlp98leeyw2qyps5tkfxrhpkvrvyzhjnd6rua46mf8qpva38f https://files.functional.cafe/accounts/avatars/110/853/908/057/317/071/original/d2d2d25541c45944.jpg https://files.functional.cafe/accounts/avatars/110/853/908/057/317/071/original/d2d2d25541c45944.jpg https://njump.me/nevent1qqs9wup9d0y037ylqeq55ndcyqws4enwvdsccn2mvnrzya5y5dawgzszyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyuk2quad In reply to <a href='/nevent1qqsxzgwvyemhfzqrlrvktdhgl2xd9nut80h20vqzyuef9tdk8p4dvfqmwnvta'>nevent1q…nvta</a><br/>_________________________<br/><br/>If only there were some extremely well financed companies with a sudden interest in mathematics, who might donate some funds to support this 2026-10-23T08:02:22Z https://njump.me/nevent1qqs2qe5dhga4zwahudsgztj8mykzgt3djzldzqmvl6p23drqj2wpvkszyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyupjrtyd We have two Associate Professorship with Tutorial Fellowship positions open, one at Wadham College and one at Christ Church. Despite the odd names, these are our standard academic faculty positions. Both also have quite generous additional housing allowances. Closing date 16th Dec. Happy to answer any questions. <a href="https://www.cs.ox.ac.uk/aboutus/vacancies/vacancy-faculty-hiring.html">https://www.cs.ox.ac.uk/aboutus/vacancies/vacancy-faculty-hiring.html</a> 2026-09-09T14:47:46Z https://njump.me/nevent1qqsdx0ewc3jj6kmge5rjg9y5g84gvvxrtlk0dseqmgvfh4hmk6thmvqzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyuy4scyn Sent off to the publisher today. At last! Still got the index, the solutions to exercises, and a proofread to go. But the end is in sight.<br/> <img src="https://files.functional.cafe/media_attachments/files/116/817/781/342/594/500/original/6c0cbfaf7a264c47.jpg"> <br/> 2026-06-26T18:18:56Z https://njump.me/nevent1qqs9w0lqwywrdsckrhdv5f97fgkqwhy3mhkrjser38vvuzs2q5gk00qzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyuaymmuz In reply to <a href='/nevent1qqsqfgnm5eg5nealnmjgaanxq4xy46zgrmdjejc7l48ld7xjz3ad9qg6gu8x7'>nevent1q…u8x7</a><br/>_________________________<br/><br/>When the monoid is sequences with concatenation, the star gives infinite periodic sequences (or the empty sequence). Those aren&#39;t *the* maximal events, but they are maximal. 2026-06-25T14:40:42Z https://njump.me/nevent1qqswt4zh0seqlah22xef7nw0kzzzwtf6v76nhqj7usua92jjx86wxlszyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyuplqwdq In reply to <a href='/nevent1qqsf3xqr6gkhjq5zyxw9v7uz8akdfexlk0d5ka77zs8acgrpazlkk9qn4z8dm'>nevent1q…z8dm</a><br/>_________________________<br/><br/>It was cited above by [@leon_p_smith](<a href="https://ioc.exchange/@leon_p_smith">https://ioc.exchange/@leon_p_smith</a> ) - &#34;Enumerating the Rationals&#34; <a href="https://www.cs.ox.ac.uk/publications/publication1664-abstract.html">https://www.cs.ox.ac.uk/publications/publication1664-abstract.html</a> 2026-05-31T06:50:45Z https://njump.me/nevent1qqstp56hcmrjjtnfx047nqqzhhv8e83dz65shed4wefdcmjq6v44hugzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyu9ntafn In reply to <a href='/nevent1qqsqhp6hhwp0g6lwa5qu78afardz7jpgh6dcgp8rqlfq749ckgyhgkq0ret4n'>nevent1q…et4n</a><br/>_________________________<br/><br/>said &#34;at least for the purposes of elementary education, I think the Stern-Brocot tree is a bit more naturally motivated, as it is a binary search tree&#34;.<br/><br/>The ordering is indeed a nice property, and it is a shame to lose it. But there are at least two benefits that the Calkin-Wilf tree has over Stern-Brocot - both discussed at considerable length in my paper.<br/><br/>One benefit is that the parent-child relationship in C-W is easily explained: the path from any element to the root traces Euclid&#39;s algorithm. I know of no such relationship for S-B.<br/><br/>The second benefit (due to Moshe Newman) is that there a simple transformation that takes each element not on the right edge to its right neighbour. But even better, precisely the same transformation also takes an element on the right edge to the one on the left edge one level deeper. This is the transformation that takes `x` to `1 / ([x] + 1 - {x})`, where `[x]` and `{x}` are the integer part and fractional part respectively of rational `x`. Iterating this function starting with `1` enumerates the rationals!<br/><br/><span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub1nf4p4rh06z6n6lsvje4txk7eqs23y3hs8vd7nraq6tgwady5qvsqy3nqe4" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>John Carlos Baez</span> (<span class="italic">npub1nf4…nqe4</span>)</a></span> 2026-05-30T11:37:05Z https://njump.me/nevent1qqsgx9t4u5zje2smkjzu33a70kzck0n7t5rfj9skgn2tq4770cq37wszyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyur3rawx In reply to <a href='/nevent1qqs83rws69rvnzewhe0e75382v0hqew4agsfqncwjyh25uqxlv0s6lg46nv59'>nevent1q…nv59</a><br/>_________________________<br/><br/>Yes! You know about Tymocko&#39;s &#34;A Geometry of Music: Harmony and Counterpoint in the Extended Common Practice&#34; <a href="https://share.google/DQB40p7DcQsXagMLe">https://share.google/DQB40p7DcQsXagMLe</a> I presume? 2026-05-15T06:31:31Z https://njump.me/nevent1qqsrkt5mwp9lh065vemndk2yx3fjqqgqcr6c85ht98fnvahsug2v32szyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyugusllq In reply to <a href='/nevent1qqs2vlq24lsyt42p7ft7krz3vfche9n5ljp8vqkdq52gl3wxdgf8dfqas9uxu'>nevent1q…9uxu</a><br/>_________________________<br/><br/>I learned in Korea recently that North Korea is much more worried about the influence of K-Culture (music, drama, etc) than about military interventions or poverty. And that (South) Korea is the number one per capita consumer of garlic. 2026-05-07T20:09:30Z https://njump.me/nevent1qqsftjswq4e63qxwhp3k2j9zljtkpjug3rgglr69twht7jj6zkx0lfczyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyuu2ns3l In reply to <a href='/nevent1qqsq5v6l5nkf9rflk0p9zt60szkp3jhc7tqdudw5c85kalcgcg02ypq4lh69x'>nevent1q…h69x</a><br/>_________________________<br/><br/>Um... books? 2026-01-24T16:37:02Z https://njump.me/nevent1qqspdkgkqsv7eh0j5mxqtud30fuyr07jzp3h7537qgfsjmkpfcgkygszyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyulgg2q7 In reply to <a href='/nevent1qqs99jg76re9qp7wrm4t5v499yflqynzsr9t9vg8u7cdrt5u8vvue4gr85cqh'>nevent1q…5cqh</a><br/>_________________________<br/><br/>something something enlightenment? 2025-09-26T17:45:22Z https://njump.me/nevent1qqsgjrx2xhd2yv6x3agn5ev7edgt4e2drfqams402fpreujcqzckedgzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyu4k4nkj In reply to <a href='/nevent1qqsxsvd545qexvmy4wj8wtfhl4vhsgquyrls6lyshp07g72y6s6p96gjhwwmh'>nevent1q…wwmh</a><br/>_________________________<br/><br/>At least &#34;unseemly&#34;, as she said. I agree that it would be fraudulent to list the Saudi institution as her *main* affiliation. But not fraudulent to accept an adjunct position, plus cash, and list them as a secondary affiliation - mere (legal) prostitution. 2025-06-29T10:29:51Z https://njump.me/nevent1qqsf7z259fusza47lg2gzl9jw5l34ygpr43x7y4mrjzex6qg9hkt2rqzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyu72yrym In reply to <a href='/nevent1qqswysu5enqzgtdr9ed7a58kxkze637yvafsmt0ty8ggvc7tx5hlngqv8hqf4'>nevent1q…hqf4</a><br/>_________________________<br/><br/>I agree that it&#39;s usually fraud for them to claim the Saudi institution as their primary affiliation. But I&#39;m not sure I&#39;d say it&#39;s more than distasteful academic prostitution to accept Saudi money to be a &#34;visiting&#34; or &#34;adjunct&#34; prof then add them to your publications as a secondary affiliation. 2025-06-28T20:00:17Z https://njump.me/nevent1qqst6y9628wfx3xrr53d602amg0s9j6dq49nech98tppm6zma8k8f0czyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyu7anm2g How your email finds me.<br/> <img src="https://functional.cafe/system/media_attachments/files/113/673/538/772/517/426/original/a27d97e01ac83005.jpg"> <br/> 2024-12-18T11:16:06Z https://njump.me/nevent1qqs98jcu0a5krmu485n8dnn4m6plztw8wcv3hhk6t9cwp400h2la84szyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyu67eu7a In reply to <a href='/nevent1qqs2gzah8l8gkp276njg4ezr8t3q468uhmstnw82fr86v7605e9n95sfenpuw'>nevent1q…npuw</a><br/>_________________________<br/><br/>Literate programs? 2024-11-18T18:09:01Z https://njump.me/nevent1qqsq5xc9rhndpjq9t54v3av3eyx2v2jc6puyq0ypguvyur62c5mkmpgzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyudxgezq In reply to <a href='/nevent1qqst6e8yuz5unt8fenttmzc00sctgdrq4ltfkagkdq0c4cxu5hwk7jc8205rp'>nevent1q…05rp</a><br/>_________________________<br/><br/>Do come and visit! 2024-11-01T12:26:30Z https://njump.me/nevent1qqsgld382zs4jd5jz7p5vz7gd2lph0mxzzc7l600lsweg200we7adwqzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyunh03zm In reply to <a href='/nevent1qqs8qlqnvujrp7ddcvvudldwfc5gujjavggpfdhnqyspz5wz9vhsl4gujwdh4'>nevent1q…wdh4</a><br/>_________________________<br/><br/>The Paul Spade book is in the Bodleian Library. Are you still in the UK? 2024-10-31T15:27:45Z https://njump.me/nevent1qqs8farsqrlcyxpngry0ekl439lulwq4csvl8mwwz7n2pqg9g5md7nqzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyu5j5l9g In reply to <a href='/nevent1qqsfxatx35as6fxlvtxy56pk8y6dfa7cq8mt7lu73zcsv3cvv38ax7qet4eg9'>nevent1q…4eg9</a><br/>_________________________<br/><br/>The &#34;professional&#34; degrees (law, medicine, theology) followed the quadrivium. But these again qualified you as a Bachelor of the relevant subject. in Oxford, they sometimes still do: eg the Bachelor of Civil Law (BCL) degree is an advanced degree, essentially a master&#39;s. 2024-10-31T12:12:15Z https://njump.me/nevent1qqsfxatx35as6fxlvtxy56pk8y6dfa7cq8mt7lu73zcsv3cvv38ax7qzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyurypw7u In reply to <a href='/nevent1qqsqhkdujz620zupsxxxqspc0jgyuetnjl46a6vemnpdktnw7p4z5mcd8ad2q'>nevent1q…ad2q</a><br/>_________________________<br/><br/>Bear in mind that &#34;undergraduate&#34; is really an anachronism. As I understand it, students at mediaeval universities, like Oxford in the 1300s, studied the liberal arts: the trivium (grammar, logic, rhetoric) then the quadrivium (arithmetic, geometry, music, astronomy). Completing that in six years qualified you as a Master of Arts; Wikipedia says that you could get the Bachelor of Arts after three or four years. By modern analogy, I&#39;d say that it&#39;s only as a master&#39;s student that you get to study these sophisms. However, they did start younger: from 14 at Oxford. <a href="https://en.wikipedia.org/wiki/Medieval_university">https://en.wikipedia.org/wiki/Medieval_university</a> 2024-10-31T12:08:33Z https://njump.me/nevent1qqs85mjglu8aduqfasnl6he3uv69ec5fmpsf84d69ypurp9lg824uqszyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyu602c58 In reply to <a href='/nevent1qqsyr58zzl2frx7n5vqgkt072r3mk9rrlmnspmktgljhcfkyskevv2sq0qrs8'>nevent1q…qrs8</a><br/>_________________________<br/><br/>I agree with all those facts. But if it were me choosing the terminology, I would have reserved the term &#34;total order&#34; for an ordering (reflexive, transitive) that is also total (𝑥≤𝑦 or 𝑦≤𝑥). And then &#34;linear order&#34; for a total order that is also antisymmetric. 2024-10-16T08:30:05Z https://njump.me/nevent1qqsfv2ahu8kk9j3h04mn3f2s2q7yfny2punk809jz605krywzkqnw5gzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyuc7xy0h In reply to <a href='/nevent1qqsrphp4wfpx76kc9ma5vmjlvtle49ahthyqs2r0p2kjxawl6p8lrys0ay9ad'>nevent1q…y9ad</a><br/>_________________________<br/><br/>That would be my intuition too, but it&#39;s not (my understanding of) standard terminology, which requires antisymmetry of a total aka linear order. 2024-10-15T19:40:01Z https://njump.me/nevent1qqst6cz98cglm87xdua072vmetjr9k3l3xfa02lak3l5ektczzwfelgzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyusk79hh In reply to <a href='/nevent1qqs297vj9tt2xkredxza3gksgpfgj6zepwxxp7gkarnaemp5h3w8uaqrhkmmp'>nevent1q…kmmp</a><br/>_________________________<br/><br/>It feels sad to me that the most natural ordering-like thing from a categorical perspective is a preorder, which is not properly &#34;an order&#34;. 2024-10-15T16:29:59Z https://njump.me/nevent1qqs297vj9tt2xkredxza3gksgpfgj6zepwxxp7gkarnaemp5h3w8uaqzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyut5zfxt In reply to <a href='/nevent1qqswwcqck0mfy90hrpg4yz8vdaupgq23np3ur35qtu5w6cs9ly9u7jss3240x'>nevent1q…240x</a><br/>_________________________<br/><br/>By this philosophy, I suppose a preorder is not really an order, but something less? What would you say then is morally &#34;an order&#34;: a partial order? 2024-10-15T16:28:40Z https://njump.me/nevent1qqs06uqne0uqh3fwywl3zlveu7t3q3myvjg4r99hep9mm0sper7phrqzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyu7gna78 In reply to <a href='/nevent1qqszmq66kq3r6xhlcj4fa7jyujvezjmu37ytkt79g8tmmlpdfx46sygh8fyx5'>nevent1q…fyx5</a><br/>_________________________<br/><br/>Anything better than &#34;total preorder&#34;? 2024-10-15T15:40:26Z https://njump.me/nevent1qqszmq66kq3r6xhlcj4fa7jyujvezjmu37ytkt79g8tmmlpdfx46sygzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyutsvejx What do you call a preorder that is total (for all x and y, either x&lt;=y or y&lt;=x) but not antisymmetric (there are distinct x,y with x&lt;=y&lt;=x)? For example, sequences ordered by length. The accepted definitions I see online of &#34;total order&#34; and &#34;linear order&#34; coincide with &#34;total partial order&#34;. Which seems perverse. 2024-10-15T15:39:50Z https://njump.me/nevent1qqsw5xk0vmaxm2mams464a2488ch0hl0avz5ppx6ah08xwpjsca73agzyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyufn33r4 <span itemprop="mentions" itemscope itemtype="https://schema.org/Person"><a itemprop="url" href="/npub1zx7w7ygfym5ktpggeuy904qgvqwpqcaysf82hzn9aq2tl46pnlps50gxhk" class="bg-lavender dark:prose:text-neutral-50 dark:text-neutral-50 dark:bg-garnet px-1"><span>Nathan Corbyn</span> (<span class="italic">npub1zx7…gxhk</span>)</a></span> Too much time on your hands, waiting for a download? 2024-09-18T20:16:27Z https://njump.me/nevent1qqsw8mpljwk7s89a2xxc272de9292hq4zf2ajp64xw5e6rn8n282f5szyzx5k2luv5ahuy5ll8y3egqsxz3weycwuxesdss272dhg0nkhtdyuadkmaq Can anyone point me to the source of this David Parnas quotation about certifying software engineers? &#34;When someone builds a bridge, he uses engineers who have been certified as knowing what they are doing. Yet when someone builds you a software program, he has no similar certification, even though your safety may be just as dependent upon that software working as it is upon the bridge supporting your weight.&#34; 2024-09-05T15:37:29Z