ref

Consider this code: #include <iostream> #include <functional> int xx = 7; template<class T> void f1(T arg) { arg += xx; } template<class T> void f2(T arg) { arg = xx; } int main() { int j; j=100; f1(std::ref(j)); std::cout << j << std::endl; j=100; f2(std::ref(j)); std::cout << j << std::endl; } When executed, this code outputs 107 100 I would have expected the second value to be 7 rather than 100. What am I missing? A small modification to f2 provides the clue: template<class T> void f2(T arg) { arg.get() = xx; } This now does what you expect. This has happened because std::ref returns a std:

I tried this earlier today: public interface IFoo { IEnumerable<int> GetItems_A( ref int somethingElse ); IEnumerable<int> GetItems_B( ref int somethingElse ); } public class Bar : IFoo { public IEnumerable<int> GetItems_A( ref int somethingElse ) { // Ok... } public IEnumerable<int> GetItems_B( ref int somethingElse ) { yield return 7; // CS1623: Iterators cannot have ref or out parameters } } What's the rationale behind this? C# iterators are state machines internally. Every time you yield return something, the place where you left off should be saved along with the state of local variables

I have some questions regarding this program: #include <iostream> #include <type_traits> #include <functional> using namespace std; template <typename T> void foo ( T x ) { auto r=ref(x); cout<<boolalpha; cout<<is_same<T&,decltype(r)>::value; } int main() { int x=5; foo (x); return 0; } The output is: false I want to know, if std::ref doesn't return the reference of an object, then what does it do? Basically, what is the difference between: T x; auto r = ref(x); and T x; T &y = x; Also, I want to know why does this difference exist? Why do we need std::ref or std::reference_wrapper when we

I'm assuming the virtual DOM, and that React takes care of it with diff'ing. But I had a recruiter say that ref's affect the actual DOM, I can't see how this can be. I assume that they were just mistaken. Refs should reference the actual DOM. One usage of Refs is integrating with third-party DOM libraries, so you can directly modify the DOM using Refs. If Refs reference the virtual DOM, I don't think the demand can be meet. You modify a virtual DOM, but you can't make sure the modification would be synchronized to the actual DOM. Besides, if you want to modify actual DOM when using react, you

What is the difference between public function Foo(ref Bar bar) { bar.Prop = 1; } public function Foo(Bar bar) { bar.Prop = 1; } essentially what is the point of "ref". isn't an object always by reference? The point is that you never actually pass an object . You pass a reference - and the argument itself can be passed by reference or value. They behave differently if you change the parameter value itself, e.g. setting it to null or to a different reference. With ref this change affects the caller's variable; without ref it was only a copy of the value which was passed, so the caller doesn't