Calling a constructor to re-initialize object

It's possible, although it's a very bad idea. The reason why is that without calling the destructors on the existing object, you are going to leak resources.

With that major caveat, if you insist on doing it, you can use placement new.

// Construct the class
CLASS cl(args);

// And reconstruct it...
new (&cl) CLASS(args);

Literally? Yes, by using placement new. But first you have to destruct the previously constructed object.

SomeClass object(1, 2, 3);
...
object.~SomeClass(); // destruct
new(&object) SomeClass(4, 5, 6); // reconstruct
...
// Final destruction will be done implicitly

The value of this does not go beyond purely theoretical though. Don't do it in practice. The whole thing is ugly beyond description.

Sort of. Given a class A:

A a;
...
a = A();   

the last statement is not initialisation, it is assignment, but it probably does what you want.