Here’s the mathematical solution which can be applied in any language: x = x0 + r * cos(theta) y = y0 + r * sin(theta) x0 and y0 are the coordinates of the centre, r is the radius, and theta is in radians. The angle is measured anticlockwise from the x-axis. This is the code … Read more
Take advantage of integer division, which truncates the decimal portion of the quotient. To make it look like it’s rounding up, add 99 first. int rounded = ((num + 99) / 100 ) * 100; Examples: 801: ((801 + 99) / 100) * 100 → 900 / 100 * 100 → 9 * 100 = … Read more
I don’t know Scala, but in Java new BigDecimal(1.1) initializes the BigDecimal with a double value and thus it is not exactly equal to 1.1. In Java you have to use new BigDecimal(“1.1”) instead. Maybe that will help in Scala as well.
Perl 130 chars So long as external libraries are permitted: use Algorithm::Permute”permute”; permute{for$x(@a=qw(+ – / *)){for$y(@a){$_=”@ARGV”;s/ /$x/;s/ /$y/;printf” $_ = %.0f”,eval}}}@ARGV 2nd newline is significant. Without a module, and assuming that all three inputs are distinct, here’s another solution: @n=& ARGV; @o=( q[+], “-“, q{/}, ‘*’ );; for$ {a}(@ n){ for $b(@n){for$c(@ {n}){ for $x( … Read more
So how does one identify if a matrix is truly singular? (In MATLAB, without using paper and pencil or symbolic computations, or hand written row operations?) The textbooks sometimes tell students to use the determinant, so I’ll start there. In theory, one can simply test if the determinant of your matrix is zero. Thus M … Read more
Pythagorean Triples make a good example for claiming “for loops considered harmful“, because for loops seduce us into thinking about counting, often the most irrelevant part of a task. (I’m going to stick with pseudo-code to avoid language biases, and to keep the pseudo-code streamlined, I’ll not optimize away multiple calculations of e.g. x * … Read more
If you have a shuffled desk, into which you wish to shuffle a batch of new cards (and you know that none of the cards are duplicates), then I think the following is valid. ForEach card in batch: gap = random(deck.size() + 1) # choose a gap between cards, before first, or after last. deck.insertAt(gap,card) … Read more
Here’s an implementation for torsion angle over the full 2pi range that is a bit faster, doesn’t resort to numpy quirks (einsum being mysteriously faster than logically equivalent code), and is easier to read. There’s even a bit more than just hacks going on here — the math is different too. The formula used in … Read more
Based on the comments by @CodeInChaos and @Alexandre C, I was able to throw together some code to reproduce the issue on my PC (Win7 x64, .NET 4.0). It appears this issue is due to the denormal control that can be set using _controlfp_s. The value of double.Epsilon is the same in both cases, but … Read more
SQL Fiddle select “date”, shop_id, amount, extract(dow from date), case when row_number() over (order by date) > 3 then avg(amount) OVER ( ORDER BY date DESC ROWS BETWEEN 1 following AND 3 FOLLOWING ) else null end from ( select * from ro where extract(dow from date) = 4 ) s What is wrong with … Read more