The following function (in my intention) is to take an rvalue and present it as it was an lvalue. auto constexpr RtoL = [](auto&& r) -> decltype(auto) { static_assert(std::is_rvalue_ref...

When a variable that is about to go out of scope is returned or thrown, its resources can be reused i.e. it can be moved from, as the following C++ program shows: #include <iostream> struct ...

I'm trying to understand the C++11 concepts. The standard draft which I have says: An xvalue (an “eXpiring” value) also refers to an object, usually near the end of its lifetime (so that its r...

The C++ standard says the following about 'xvalues' (N4762 § 7.2.1.4): An expression is an xvalue if it is: - . . . - a class member access expression designating a non-static data member of ...

C++11 introduced new value categories, one of them is xvalue. It is explained by Stroustrup as something like (im category): "it is a value, which has identity, but can be moved from". Another so...

I'm sorry for the broadness of the question, it's just that all these details are tightly interconnected.. I've been trying to understand the difference between specifically two value categories -...

I tried to understand lvalue and rvalue in C++11. So I wrote a test code: int x = 10; int foo() { return x; } int& bar() { return x; } int&& baz() { return 10; } int main() { int&amp...

Following the well accepted answer to this question Do rvalue references allow dangling references? It would seem that xvalues do not have their lifetime extended when assigned to a rvalue referenc...

Consider the minimal example below: #include<utility> struct S { }; int main() { S s; std::move(s) = S{}; } It compiles with no errors. If I use non class types instead, I get an error...

I want to calculate the distance between x-value of two squares positioned in a view. I did not work because in the frame there is also the y-value and do not know how to select only one. how can ...

Somewhat surprisingly (to me), the following two programs compile to different outputs, with the latter one having much better performance (tested with gcc and clang): #include <vector> int ...

Here is some example code: #include <iostream> class Foo { public: explicit Foo(int x) : data(x) {}; Foo& operator++() { data += 1; return *this; } void *get_addr() { return ...

I read the standard on xvalue. It is closely associated with rvalue reference expression. But when programming, I really cannot find scenarios that needs xvalue. For example: function myClass&...

I am currently writing my degree dissertation and it involves also some explaining of the theory behind C++11 which is really fine as C++ is my programming language of choice and the standard is mo...

If I write the following code: #include <iostream> using namespace std; int main() { cout << &(int &&)123 << endl; return 0; } Then g++ complains: foo.cc: In f...

(Prompted by an answer.) Given N3290, §7.1.6.2p4, where the list items are unnumbered, but numbered here for our convenience: The type denoted by decltype(e) is defined as follows: if e is...