111 points by BerislavLopac 2 days ago | 28 comments
XOR(greenend.org.uk) Recently I was called on to explain the ‘XOR’ operator to somebody who vaguely knew of its existence, but didn’t have a good intuition for what it was useful for and how it behaved.
Gödel's Loophole(wikipedia.org) Gödel's Loophole is a supposed "inner contradiction" in the Constitution of the United States which Austrian-American logician, mathematician, and analytic philosopher Kurt Gödel postulated in 1947.
Sequent Calculus and Notation – Par Part 1(ryanbrewer.dev) This post is the first in a series on Logic. These ideas are very useful in understanding many important papers on programming language theory, especially papers on type theory and the lambda calculus. I will start with an explanation of sequents and Sequent Calculus as a system for doing logic, then I'll dive into linear logic in the next post. I'll finish the trilogy with a post on Par and computational interpretations of classical logic.
Who Can Understand the Proof? A Window on Formalized Mathematics(stephenwolfram.com) For more than a century people had wondered how simple the axioms of logic (Boolean algebra) could be. On January 29, 2000, I found the answer—and made the surprising discovery that they could be about twice as simple as anyone knew. (I also showed that what I found was the simplest possible.)
Transcendental Syntax(github.com/engboris) The transcendental syntax is a method of constructing logical abstractions from a low-level elementary and "logic-agnostic" language.
The Hoare Cube(wordpress.com) I wrote earlier this year about my attempt to understand the repercussions of toggling and when giving a semantics to Hoare triples.
Beauty of the Gentzen System(wyounas.github.io) Gentzen system, created by German mathematician Gerhard Gentzen, is a deductive system which can be used to prove propositional formulas. I recently learned about it while I was reading Ben-Ari’s fantastic book on mathematical logic [1] and I like its simplicity.
A boy girl paradox – or maybe not?(shankwiler.com) The most liked comment answers 1/2, but the user got worn down by others until he recanted and agreed that the answer is 1/3. Many other comments give lengthy explanations as to why the answer is 1/3.
8 points by sandwichsphinx 101 days ago | 0 comments
Question Sets and All Paths(andrewpwheeler.com) I was nerd-sniped with a question at work the other day. The set up was like this, imagine a survey where all of the questions have yes-no answers. Some of the answers are terminating, so if you answer No to a particular question, the questions stop. But some if you reach that part of the tree will keep going.
The box problem that baffled the boffins(theguardian.com) Earlier today I set you the following puzzle, which has been doing the rounds in the academic community, because of its counter-intuitive result. Here it is again with the solution.
Mathiness(votito.com) Mathiness is a term for calculations and formulas that may look and feel like rigorous mathematics but lack true analytical rigor or validity, and often disregard logical coherence or factual accuracy.