C++ deleted constructors

Question

Say I have this structure:

struct F
{
    int& ref; // reference member
    const int c; // const member
    // F::F() is implicitly defined as deleted
};

That is from cppreference. As I understand from the documentation the constructor of F is considered deleted because it has a reference variable which refers to nothing. So one cannot declare a variable of type F like so: F variableName; as there will be errors such as: uninitialized reference member in struct F.

I understand this however I do not understand what such a structure would be good for if you cannot even declare a variable of its type. Could such a data type be useful in some specific case?

Answer 1

Since F is an aggregate you can use aggregate initialization:

int a = 42;
F f1 = {a, 13};

// or

F f2{a, 9};

Live demo.

A class type (typically, struct or union) is an aggregate if it has:

• no private or protected non-static data members
• no user-provided, inherited, or explicit (since C++17) constructors (explicitly defaulted or deleted constructors are allowed) (since C++11)
• no virtual, private, or protected (since C++17) base classes
• no virtual member functions