~ is the unary one’s complement operator — it flips the bits of its operand. ~0 = 0xFFFFFFFF = -1 in two’s complement arithmetic, ~x == -x-1 the ~ operator can be found in pretty much any language that borrowed syntax from C, including Objective-C/C++/C#/Java/Javascript.
I think one reason it works this way is because access modifiers work at compile time. As such, determining whether or not a given object is also the current object isn’t easy to do. For example, consider this code: public class Foo { private int bar; public void Baz(Foo other) { other.bar = 2; } … Read more
Interfaces are a way to make your code more flexible. What you do is this: Ibox myBox=new Rectangle(); Then, later, if you decide you want to use a different kind of box (maybe there’s another library, with a better kind of box), you switch your code to: Ibox myBox=new OtherKindOfBox(); Once you get used to … Read more
There is a big difference between them. In C++ you don’t have to specify a class or an interface for the generic type. That’s why you can create truly generic functions and classes, with the caveat of a looser typing. template <typename T> T sum(T a, T b) { return a + b; } The … Read more
Python’s mostly implementing a pragmatically tinged flavor of command-query separation: mutators return None (with pragmatically induced exceptions such as pop😉 so they can’t possibly be confused with accessors (and in the same vein, assignment is not an expression, the statement-expression separation is there, and so forth). That doesn’t mean there aren’t a lot of ways … Read more
It turns out that SQL can be Turing Complete even without a true ‘scripting’ extension such as PL/SQL or PSM (which are designed to be true programming languages, so that’s kinda cheating). In this set of slides Andrew Gierth proves that with CTE and Windowing SQL is Turing Complete, by constructing a cyclic tag system, … Read more
Cannibalized from another post of mine, here’s more than you ever wanted to know about this. Before I start, here’s the most important thing to keep in mind about Javascript, and to repeat to yourself when it doesn’t make sense. Javascript does not have classes (ES6 class is syntactic sugar). If something looks like a … Read more
DateTime.UtcNow tells you the date and time as it would be in Coordinated Universal Time, which is also called the Greenwich Mean Time time zone – basically like it would be if you were in London England, but not during the summer. DateTime.Now gives the date and time as it would appear to someone in … Read more
Just to address the last part of your question, since that really points out the difference between a list and vector in R: Why do these two expressions not return the same result? x = list(1, 2, 3, 4); x2 = list(1:4) A list can contain any other class as each element. So you can … Read more
The @ symbol denotes an annotation type definition. That means it is not really an interface, but rather a new annotation type — to be used as a function modifier, such as @override. See this javadocs entry on the subject.