How to distinguishe declaration and use of a function?

Question

I have the following structure in the code:

while (x > 0) {
     something;
     aaa::bbb::ccc some_name(
        x,
        y
     );
}

I cannot understand what aaa::bbb::ccc some_name(. If it is a call of function, why do we need to specify its time aaa::bbb::ccc. If it is a declaration of a function, why it is done in while loop and why types of the arguments are not specified?

Answer 1

You don't specify the return type in function calls, so this cannot possibly be a function call.

As Pubby points out, it is very likely an object definition. You define an object called some_name of type aaa::bbb::ccc and pass x and y to the constructor.

Answer 2

In this particular case, it's probably constructing an object some_name of type aaa::bbb::ccc by calling its two-parameter constructor with arguments x and y.

The reason why it's done in the loop could be that the object does some useful work in its constructor and/or destructor (it could e.g. be some form of scope guard).

Answer 3

I am not quite sure what you are up to, but the

::

in C++ is called the scope-operator and is used to access namespaces, variables in namespaces or static class-members.

Usually function-declarations and definitions appear outside of functions and methods. So your code doesn't make any sense.

See here about the scope-operator. And here for declaration vs definition.