Significance of parentheses in decltype((c))?

Question

I was reading this article on Wikipedia regarding C++11 Type Inference feature.

There is an example and I quote:

#include 
int main() {         


        

Answer 1

I found a good description here. It describes the difference between:

struct A { double x; };
const A* a = new A();
...
decltype(a->x) x4; // type is double
decltype((a->x)) x5; // type is const double&

and I quote:

The reason for the difference between the latter two invocations of decltype is that the parenthesized expression (a->x) is neither an id-expression nor a member access expression, and therefore does not denote a named object. [13]

Because the expression is an lvalue, its deduced type is "reference to the type of the expression", or const double&. [10]