Cannot pass std::cout to ostream& constructor

Question

I tried to create generic stream class holder, but it seems like I cannot pass std::cout to it, the code:

#include <iostream>

struct x
{
    std::ostream &o;
    x(std::ostream &o):o(o){}
};

int main()
{
    x(std::cout);
    x.o<<"Hi\n";
    return 0;
}

fails when compiled as:

c++ str.cc -o str -std=c++11
str.cc: In function ‘int main()’:
str.cc:11:14: error: invalid use of qualified-name ‘std::cout’
str.cc:12:4: error: expected unqualified-id before ‘.’ token

Why?

Answer 1

x(std::cout);

is equivalent to

x std::cout;

which tries to declare a local variable called std::cout . That's not allowed.

If you wanted to declare a variable of type x , passing std::cout to its constructor, then that's

x x(std::cout);

although, for the sake of your sanity, it might be better to give it a different name to the class (and change the following line to use that name).

Answer 2

Use:

int main()
{
    x object(std::cout);
    object.o << "Hi\n";
    return 0;
}