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Why does Java's hashCode() in String use 31 as a multiplier?
...he multiplication overflowed, information would be lost, as multiplication by 2 is equivalent to shifting. The advantage of using a prime is less clear, but it is traditional. A nice property of 31 is that the multiplication can be replaced by a shift and a subtraction for better performance: 31 * i...
What does it mean to start a PHP function with an ampersand?
... will return a reference to a variable instead of the value.
Returning by reference is useful when
you want to use a function to find to
which variable a reference should be
bound. Do not use return-by-reference
to increase performance. The engine
will automatically optimize this on
...
@property retain, assign, copy, nonatomic in Objective-C
...
The article linked to by MrMage is no longer working. So, here is what I've learned in my (very) short time coding in Objective-C:
nonatomic vs. atomic
- "atomic" is the default. Always use "nonatomic". I don't know why, but the book I read said ...
Git submodule push
...le before add your_submodule ? I thougth the best way to add submodule was by using "add" git command. So is there another way to add submodule ?
– MrSo
Jul 4 '16 at 10:38
...
Maximum number of characters using keystrokes A, Ctrl+A, Ctrl+C and Ctrl+V
This is an interview question from google. I am not able to solve it by myself. Can somebody shed some light?
14 Answers
...
Rank function in MySQL
...:= @curRank + 1 AS rank
FROM person p, (SELECT @curRank := 0) r
ORDER BY age;
The (SELECT @curRank := 0) part allows the variable initialization without requiring a separate SET command.
Test case:
CREATE TABLE person (id int, first_name varchar(20), age int, gender char(1));
INSERT INTO ...
Does ARC support dispatch queues?
...-C object. This is documented in the <os/object.h> header file:
* By default, libSystem objects such as GCD and XPC objects are declared as
* Objective-C types when building with an Objective-C compiler. This allows
* them to participate in ARC, in RR management by the Blocks runtime and ...
Count number of rows within each group
... I don't know but this could be useful as well... df %>% group_by(group, variable) %>% mutate(count = n())
– Manoj Kumar
Dec 14 '16 at 17:57
1
...
Find out how much memory is being used by an object in Python [duplicate]
How would you go about finding out how much memory is being used by an object? I know it is possible to find out how much is used by a block of code, but not by an instantiated object (anytime during its life), which is what I want.
...
Are there any SHA-256 javascript implementations that are generally considered trustworthy?
...s other implementation platforms, this one is at least partially developed by, and to a certain extent sponsored by, Dan Boneh, who is a well-established and trusted name in cryptography, and means that the project has some oversight by someone who actually knows what he's doing. The project is also...