Problem using eof() in a while loop [C++]

I have problem with the following code.

#include<iostream>
template <class A> void reading(A &a) {
    bool x = true;
    while(x) {
        x = false;
        std::cin >> a;
        while (std::cin.fail()) {
            if (std::cin.eof()) {
                std::cout <<"You pressed CTRL+D\n";
                std::cin.clear();
                std::cin.ignore (1000000000, '\n');
            }
            else {
                std::cout <<"Give me numbers, not letters\n";
                std::cin.clear();
                std::cin.ignore(1000000000,'\n');
            }
            x = true;
        }
    }
}

int main() {

    double o[3];
    for (double &i:o)
        reading (i);
    for (int j = 0; j<3; j++)
        std::cout<<o[j]<<std::endl;   
}

In particular, when I press ctrl+d the program enter in an infinite loop. Does someone know where is the problem and what is the solution?

My goal is to make a template function that can read any kind of data and that disable the ctrl+d during the input.