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What is the difference between an int and an Integer in Java and C#?
...by reference (or more accurately have references passed by value), and are allocated from the heap. Conversely, primitives are immutable types that are passed by value and are often allocated from the stack.
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Do c++11 lambdas capture variables they don't use?
When I use [=] to indicate that I would like all local variables to be captured by value in a lambda, will that result in all local variables in the function being copied, or just all local variables that are used by the lambda ?
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What is the meaning of the term arena in relation to memory?
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An arena is just a large, contiguous piece of memory that you allocate once and then use to manage memory manually by handing out parts of that memory. For example:
char * arena = malloc(HUGE_NUMBER);
unsigned int current = 0;
void * my_malloc(size_t n) { current += n; return arena +...
Retrieving the last record in each group - MySQL
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MySQL 8.0 now supports windowing functions, like almost all popular SQL implementations. With this standard syntax, we can write greatest-n-per-group queries:
WITH ranked_messages AS (
SELECT m.*, ROW_NUMBER() OVER (PARTITION BY name ORDER BY id DESC) AS rn
FROM messages AS m...
$apply vs $digest in directive testing
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scope.$digest() will fire watchers on the current scope, and on all of its children, too. scope.$apply will evaluate passed function and run $rootScope.$digest().
The first one is faster, as it needs to evaluate watchers for current scope and its children. The second one is slower, as it...
What is the difference between persist() and merge() in JPA and Hibernate?
...these
other entities are annotated with the
cascade=PERSIST or cascade=ALL
annotation element value or specified
with the equivalent XML descriptor
element.
If X is a removed entity,
it becomes managed.
If X is a
detached object, the
EntityExistsException may be thrown
when the...
What is the reason not to use select *?
I've seen a number of people claim that you should specifically name each column you want in your select query.
20 Answers
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How to create a new (and empty!) “root” branch?
...ository. By "root" branch I mean a branch that is entirely independent of all the other branches in the repository 1 .
4 A...
Convert data.frame column format from character to factor
...e to the world of R.
mtcars #look at this built in data set
str(mtcars) #allows you to see the classes of the variables (all numeric)
#one approach it to index with the $ sign and the as.factor function
mtcars$am <- as.factor(mtcars$am)
#another approach
mtcars[, 'cyl'] <- as.factor(mtcars[...
What are all the differences between src and data-src attributes?
...ributes src and data-src have nothing in common, except that they are both allowed by HTML5 CR and they both contain the letters src. Everything else is different.
The src attribute is defined in HTML specs, and it has a functional meaning.
The data-src attribute is just one of the infinite set of...