(Resulting from my claim that “a child of 8 can understand monoids…”) Wikipedia says: “In abstract algebra, a branch of mathematics, a monoid is an algebraic structure with a single associative binary operation and an identity element.” Wolfram says: A monoid is a set that is closed under an associative…
Category: Maths
Amaze your friends, and confound your enemies!
When I was young, I read lots of books with titles (or at least subheadings) along the lines of, “Amaze Your Friends and Confound Your Enemies” – a lot of them were filled with tricks and oddities like the Birthday Paradox, or the old saw about the elephant from Denmark….
How many bugs are left? The Lincoln Index
You’re working on some software, and you have some QA folks testing it. How do you know how many bugs are left? You know the bugs that the testers find, but how can you estimate the number that aren’t yet found? If your testers work independently, and if your feature…
Explaining Maths
Recently, I was talking to my Dad about fiddling about programming the iPad (which I haven’t got around to yet) but I did mention that I might have a go at something simple just to get my feet wet. Beyond Hello, World there are many simple small-to-medium-size projects of course,…
Maths is fun
The other week, a colleague walked into my office and posed the following problem to me: For all n where n is prime and n > 3, show that n² – 1 is divisible by 24. Examples: 5² – 1 = 24; 7² -1 = 48; 11² – 1 =…
Approximating elliptical arcs with Bézier curves
In doing my modulation work with curves and ellipses, I extended the vecto function for drawing an ellipse to enable an oriented ellipse. Lately it occurred to me that this didn’t go far enough in terms of functionality, and I began wondering about how to draw part of an elliptical…
A bit of Pythagoras
Given Pythagorean triples that satisfy the Diophantine equation: a² + b² = c² where a, b and c share no common factors, one of a and b must be odd, the other must be even, and c is always odd. First, note that squares of even numbers are always divisible…
Even more on ellipses and splines
Honestly, they’re incredibly interesting. Anyway, I’ll skip straight to the pièce de résistance: This is a 4-curve cubic Bézier spline modulated onto an ellipse. The ellipse [a=4, b=3] is at an angle of π/4. C1 continuity of the complete curve is preserved. The flickr set tells the story of how…
Ellipses & Splines again
After some code cleanup and generalisation, I can now modulate whole splines onto ellipses and onto splines themselves. Here is my simple 4-bezier spline modulated onto an ellipse: And onto itself: Repeatedly modulating a spline onto itself while varying the frequency parameter leads to some interesting and fractal patterns. Nice.
Splines and modulation
My efforts to equally subdivide a curve along its length have, in part, been leading to this. First, I extended the sampling to work with splines (made up of cubic Bézier curves with c1 continuity). This shot shows 4 curves put together to form a spline: Next, I wrote some…