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#include <iostream>
class T {
public:
T(const std::string& a) : name{a} {
std::cout << "Called constructor for " << name
<< " (" << this << ")" << std::endl;
}
~T() {
std::cout << "Called destructor for " << name
<< " (" << this << ")" << std::endl;
}
T(T& other) : name{other.name} {
std::cout << "Copy constructor called for " << name
<< " (" << this << " copied from "
<< &other << ")" << std::endl;
}
T& operator=(T& other) {
name = other.name;
std::cout << "Copy assignment called for " << name
<< " (" << this << " copied from "
<< &other << ")" << std::endl;
return *this;
}
T(T&& other) : name{other.name} {
std::cout << "Move constructor called for " << name
<< " (" << this << " moved from "
<< &other << ")" << std::endl;
}
T& operator=(T&& other) {
name = other.name;
std::cout << "Move assignment called for " << name
<< " (" << this << " moved from "
<< &other << ")" << std::endl;
return *this;
}
private:
std::string name;
};
T do_nothing_and_return(T x) {
return x;
}
T create(const std::string& str) {
return T(str);
}
int main() {
//T bad; // Compile-time error: no default constructor.
std::cout << "---------- Declaring a simple variable ----------" << std::endl;
T a("A");
std::cout << std::endl;
// Now we can see that objects are indeed scope-bound: they
// are destroyed when they go out of scope.
std::cout << "--- Declaring a variable in a temporary scope ---" << std::endl;
{
std::cout << "Entering temporary scope" << std::endl;
T b("short-lived");
std::cout << "Exiting temporary scope" << std::endl;
}
std::cout << "Out of temporary scope" << std::endl;
std::cout << std::endl;
std::cout << "------------ Constructing by copying ------------" << std::endl;
T b("B");
T c(b);
T d = b; // This is also a copy constructor, not a copy assignment
std::cout << std::endl;
// Copy assignment operators differ from copy constructors in that they
// should also clean up the resources for the copied-to object.
std::cout << "---------------- Copy assignment ----------------" << std::endl;
c = b;
std::cout << std::endl;
std::cout << "------------ Constructing by moving -------------" << std::endl;
T e(do_nothing_and_return(b));
std::cout << std::endl;
std::cout << "---------------- Move assignment ----------------" << std::endl;
e = create("E");
std::cout << std::endl;
std::cout << "------------- Destroying everything -------------" << std::endl;
return 0;
}
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