Is there a difference between copy initialization and direct initialization?

Question

Suppose I have this function:

void my_test()
{
    A a1 = A_factory_func();
    A a2(A_factory_func());

    double b1 = 0.5;
    double b2(0.5);

    A c1;
         


        

Answer 1

This is from C++ Programming Language by Bjarne Stroustrup:

An initialization with an = is considered a copy initialization. In principle, a copy of the initializer (the object we are copying from) is placed into the initialized object. However, such a copy may be optimized away (elided), and a move operation (based on move semantics) may be used if the initializer is an rvalue. Leaving out the = makes the initialization explicit. Explicit initialization is known as direct initialization.