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How to specialize std::hash::operator() for user-defined type in unordered containers?
...hash function is this:
namespace std {
template <> struct hash<Foo>
{
size_t operator()(const Foo & x) const
{
/* your code here, e.g. "return hash<int>()(x.value);" */
}
};
}
(Other popular specializations that you might consider supporting are std::...
how to provide a swap function for my class?
... with SFINAE.
// some algorithm in your code
template<class T>
void foo(T& lhs, T& rhs) {
using std::swap; // enable 'std::swap' to be found
// if no other 'swap' is found through ADL
// some code ...
swap(lhs, rhs); // unqualified call, uses ADL and fi...
Why is rbindlist “better” than rbind?
...018-06-12 01:41:40 UTC
set.seed(1L)
names = paste0("V", 1:500)
cols = 500L
foo <- function() {
data = as.data.frame(setDT(lapply(1:cols, function(x) sample(10))))
setnames(data, sample(names))
}
n = 10e3L
ll = vector("list", n)
for (i in 1:n) {
.Call("Csetlistelt", ll, i, foo())
}
sy...
What is Node.js' Connect, Express and “middleware”?
...ad and install express globally (check the express guide).
Running express foo in a command line (not in node) will create a ready-to-run application named foo. Change to its (newly created) directory and run it with node with the command node <appname>, then open http://localhost:3000 and see...
What is the advantage of using Restangular over ngResource?
...RL than '/users/123'? (just playing Devil's advocate) It just seems like '/foo/123/bar/123' is a lot easier than .one('foo', 123).one('bar', 123).
– Ben Lesh
Jul 13 '13 at 17:48
5
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What happens to a declared, uninitialized variable in C? Does it have a value?
...tic) are initialized to zero:
int x; // zero
int y = 0; // also zero
void foo() {
static int x; // also zero
}
Non-static variables (local variables) are indeterminate. Reading them prior to assigning a value results in undefined behavior.
void foo() {
int x;
printf("%d", x); // the co...
What causes and what are the differences between NoClassDefFoundError and ClassNotFoundException?
...e that the class SomeClass in in your CLASSPATH.
private static SomeClass foo = new SomeClass();
Tip : To find out which jar a class belongs to, you can use the web site jarFinder . This allows you to specify a class name using wildcards and it searches for the class in its database of jars. jarh...
Which is more efficient, a for-each loop, or an iterator?
...
I believe he was saying the opposite, that foo.get(i) can be a lot less efficient. Think of LinkedList. If you do a foo.get(i) on the middle of a LinkedList it has to traverse all the previous nodes to get to i. An iterator, on the other hand, will keep a handle to...
Argparse: Required arguments listed under “optional arguments”?
...ver you want to call them):
parser = argparse.ArgumentParser(description='Foo')
parser.add_argument('-o', '--output', help='Output file name', default='stdout')
requiredNamed = parser.add_argument_group('required named arguments')
requiredNamed.add_argument('-i', '--input', help='Input file name', ...
What's the difference between “declare class” and “interface” in TypeScript
...e.
For example when we have the following interface:
interface test {
foo: number,
bar: string,
}
The objects which we define which have this interface type need to match the interface exactly:
// perfect match has all the properties with the right types, TS compiler will not complain.
c...