You misunderstood what the is operator tests. It tests if two variables point the same object, not if two variables have the same value. From the documentation for the is operator: The operators is and is not test for object identity: x is y is true if and only if x and y are the … Read more
As you’ve found, JavaScript doesn’t support operator overloading. The closest you can come is to implement toString (which will get called when the instance needs to be coerced to being a string) and valueOf (which will get called to coerce it to a number, for instance when using + for addition, or in many cases … Read more
The official name is “object operator” – T_OBJECT_OPERATOR.
const string message = “Hello” + “,world” + exclam; The + operator has left-to-right associativity, so the equivalent parenthesized expression is: const string message = ((“Hello” + “,world”) + exclam); As you can see, the two string literals “Hello” and “,world” are “added” first, hence the error. One of the first two strings being concatenated … Read more
The difference is that one modifies the data-structure itself (in-place operation) b += 1 while the other just reassigns the variable a = a + 1. Just for completeness: x += y is not always doing an in-place operation, there are (at least) three exceptions: If x doesn’t implement an __iadd__ method then the x … Read more
http://en.wikipedia.org/wiki/Equals_sign#In_computer_programming In computer programming languages, the equals sign typically denotes either a boolean operator to test equality of values (e.g. as in Pascal or Eiffel), which is consistent with the symbol’s usage in mathematics, or an assignment operator (e.g. as in C-like languages). Languages making the former choice often use a colon-equals (:=) or ≔ … Read more
TL;DR We start by summarising the two behaviour of the two logical operators and and or. These idioms will form the basis of our discussion below. and Return the first Falsy value if there are any, else return the last value in the expression. or Return the first Truthy value if there are any, else … Read more
++x is called preincrement while x++ is called postincrement. int x = 5, y = 5; System.out.println(++x); // outputs 6 System.out.println(x); // outputs 6 System.out.println(y++); // outputs 5 System.out.println(y); // outputs 6
* is the “splat” operator: It takes an iterable like a list as input, and expands it into actual positional arguments in the function call. So if uniqueCrossTabs were [[1, 2], [3, 4]], then itertools.chain(*uniqueCrossTabs) is the same as saying itertools.chain([1, 2], [3, 4]) This is obviously different from passing in just uniqueCrossTabs. In your … Read more
In most cases, && and || are preferred over & and | because the former are short-circuited, meaning that the evaluation is canceled as soon as the result is clear. Example: if(CanExecute() && CanSave()) { } If CanExecute returns false, the complete expression will be false, regardless of the return value of CanSave. Because of … Read more