输入std :: function的别名

Question

I'm trying to alias the std::function type because I plan on using something else in the future. And I would like to be able to easily make that change. But I'm getting an error message from the compiler that I don't really understand. I understand what it means but I don't understand it in this context.

Example:

#include <functional>

template < typename Ret, typename... Args > using MyFunc = std::function< Ret(Args...) >;

int main(int argc, char **argv)
{
    MyFunc<void(int)> fn;

    return 0;
}

Generates:

..\main.cpp|7|required from here|
..\main.cpp|3|error: function returning a function|

Answer 1

template <typename F>
using MyFunc = std::function<F>;

void(int) is a single (function) type.

Answer 2

Even though the accepted response is right, it proposes a slightly different approach in regard of the one the OP posted.

For the sake of clarity, it must be said that also the solution the OP was using is fine.
The problem is how he was using the MyFunc type in his main function.

It shouldn't be:

MyFunc<void(int)> fn;

Instead, the following one is right:

MyFunc<void, int> fn;

Because of that, the code below works as expected:

#include <functional>

template < typename Ret, typename... Args >
using MyFunc = std::function< Ret(Args...) >;

int main(int argc, char **argv) {
    MyFunc<void, int> fn; // it was MyFunc<void(int)> fn;
    return 0;
}