How do I pass a 'general' priority_queue as function argument in c++

In my main function, I have a bunch of priority_queues all of them have int in them, but some have less<int>, others have greater<int>:

//std:: removed for clarity
priority_queue<int, vector<int>, less<int>> pq1;
priority_queue<int, vector<int>, greater<int>> pq2;

I wish to make a function that accepts two priority_queue by reference and pops the first and puts into the second.

But, this gives me an error:

void f(priority_queue<int> &from, priority_queue<int> &to) {
    int x = from.top();
    from.pop();
    to.push(x);
}

When passing my priority_queues into the function, it gives me an error. (no matching function for call)

How can I fix this without making four separate functions for 'greater<int>' and 'less<int>' combinations?

Just create a function template:

template<class C1, class L1, class C2, class L2>
void f(std::priority_queue<int, C1, L1> &from, std::priority_queue<int, C2, L2> &to) {
    int x = from.top();
    from.pop();
    to.push(x);
}

You could change the function as described in fabian's answer but instead of requiring that the target of the extraction is another priority_queue you could make it more generic by creating a function template that simply returns the extracted value.

template<class C>
auto extract_top(C& c) {
    struct popper {
        ~popper() {
            c.pop();
        }
        C& c;
    };
    popper p{c};
    return std::move(c.top());
}

You could then put the extracted value in another priority_queue or store it anywhere you'd like:

pq2.emplace(extract_top(pq1));