Implementation 1 returns the magnitude of the vector that would result from a regular 3D cross product of the input vectors, taking their Z values implicitly as 0 (i.e. treating the 2D space as a plane in the 3D space). The 3D cross product will be perpendicular to that plane, and thus have 0 X … Read more
With current logging frameworks, the question is moot Current logging frameworks like slf4j or log4j 2 don’t require guard statements in most cases. They use a parameterized log statement so that an event can be logged unconditionally, but message formatting only occurs if the event is enabled. Message construction is performed as needed by the … Read more
Check out the description of the Test-and-set machine instruction on Wikipedia, which alludes to how atomic operations are achieved at the machine level. I can imagine most language-level mutex implementations rely on machine-level support such as Test-and-set.
I faced the same problem a few weeks ago and wrote this: http://smtp4dev.codeplex.com Windows 7/Vista/XP/2003/2010 compatible dummy SMTP server. Sits in the system tray and does not deliver the received messages. The received messages can be quickly viewed, saved and the source/structure inspected. Useful for testing/debugging software that generates email.
This should work – just linearly scale the red and green values. Assuming your max red/green/blue value is 255, and n is in range 0 .. 100 R = (255 * n) / 100 G = (255 * (100 – n)) / 100 B = 0 (Amended for integer maths, tip of the hat to … Read more
Here’s my own solution, based on the idea in ask Dr. Math. I’d be happy to see your feedback. Disclaimer first. This solution is correct for spheres. Earth isn’t a sphere, and the coordinates system (WGS 84) doesn’t assume it’s a sphere. So this is just an approximation, and I can’t really estimate is error. … Read more
Are they more expensive than iterations? Yes they are. Many Lisp variants support the idea of a “tail-call optimisation” which allows many uses of a recursive function call to be converted into an iterative one (this is simplifying a bit). If tail-call is not supported, then a recursive function call will use progressively more memory … Read more
If I gather in one place any three theorists of my acquaintance, at least two of them disagree on the meaning of the term “referential transparency.” And when I was a young student, a mentor of mine gave me a paper explaining that even if you consider only the professional literature, the phrase “referentially transparent” … Read more
This gives a signed angle for any angles: a = targetA – sourceA a = (a + 180) % 360 – 180 Beware in many languages the modulo operation returns a value with the same sign as the dividend (like C, C++, C#, JavaScript, full list here). This requires a custom mod function like so: … Read more
When you need something done at least once, but don’t know the number of times prior to initiating the loop.