Remember that negative numbers are stored as the two’s complement of the positive counterpart. As an example, here’s the representation of -2 in two’s complement: (8 bits) 1111 1110 The way you get this is by taking the binary representation of a number, taking its complement (inverting all the bits) and adding one. Two starts … Read more
As always with these questions, the JLS holds the answer. In this case §15.26.2 Compound Assignment Operators. An extract: A compound assignment expression of the form E1 op= E2 is equivalent to E1 = (T)((E1) op (E2)), where T is the type of E1, except that E1 is evaluated only once. An example cited from §15.26.2 […] the following code is … Read more
Comma operator is applied and the value 5 is used to determine the conditional’s true/false. It will execute blah() and get something back (presumably), then the comma operator is employed and 5 will be the only thing that is used to determine the true/false value for the expression. Note that the , operator could be … Read more
=~ is the operator testing a regular expression match. The expression /9eaf/ is a regular expression (the slashes // are delimiters, the 9eaf is the actual regular expression). In words, the test is saying “If the variable $tag matches the regular expression /9eaf/ …” and this match occurs if the string stored in $tag contains … Read more
You shouldn’t worry about performance unless your code is in a tight inner loop, and is actually a performance problem. Instead, use code that best expresses your intent. Some people like lambdas, some like itemgetter. Sometimes it’s just a matter of taste. itemgetter is more powerful, for example, if you need to get a number … Read more
The short answer is no. ECMAScript (the standard JS is based on) does not support operator overloading. As an aside, in ECMAScript 7, you’ll be able to overload a subset of the standard operators when designing custom value types. Here is a slide deck by language creator and Mozilla CTO Brendan Eich about the subject. … Read more
It is the power operator. From the Python 3 docs: The power operator has the same semantics as the built-in pow() function, when called with two arguments: it yields its left argument raised to the power of its right argument. The numeric arguments are first converted to a common type, and the result is of … Read more
a += b is short-hand for a = a + b (though note that the expression a will only be evaluated once.) a =+ b is a = (+b), i.e. assigning the unary + of b to a. Examples: int a = 15; int b = -5; a += b; // a is now 10 … Read more
When Python attempts to multiply two objects, it first tries to call the left object’s __mul__() method. If the left object doesn’t have a __mul__() method (or the method returns NotImplemented, indicating it doesn’t work with the right operand in question), then Python wants to know if the right object can do the multiplication. If … Read more
Rule of thumb: Use -a and -o inside square brackets, && and || outside. It’s important to understand the difference between shell syntax and the syntax of the [ command. && and || are shell operators. They are used to combine the results of two commands. Because they are shell syntax, they have special syntactical … Read more