Real life examples of xvalues, glvalues, and prvalues?

Question

I was wondering if anyone could tell or explain some real life examples of xvalues, glvalues, and prvalues?. I have read a similar question :

What are rvalues, lvalues, xvalues, glvalues, and prvalues?

but I did not understand what everyone meant. Can anyone explain in what cases these values are important and when one should use them?

Answer 1

Consider the following class:

class Foo {     std::string name;  public:      Foo(std::string some_name) : name(std::move(some_name))     {     }      std::string& original_name()     {         return name;     }      std::string copy_of_name() const     {         return name;     } }; 

The expression some_foo.copy_of_name() is a prvalue, because copy_of_name returns an object (std::string), not a reference. Every prvalue is also an rvalue. (Rvalues are more general.)

The expression some_foo.original_name() is an lvalue, because original_name returns an lvalue reference (std::string&). Every lvalue is also a glvalue. (Glvalues are more general.)

The expression std::move(some_name) is an xvalue, because std::move returns an rvalue reference (std::string&&). Every xvalue is also both a glvalue and an rvalue.

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Note that names for objects and references are always lvalues:

std::string a; std::string& b; std::string&& c; 

Given the above declarations, the expressions a, b and c are lvalues.