Refer to the definition of std::function.

template<class R, class... ArgTypes>
class function<R(ArgTypes...)> {
public:
    //...
    function& operator=(const function&);
    function& operator=(function&&);
    function& operator=(nullptr_t);
    template<class F> function& operator=(F&&);
    template<class F> function& operator=(reference_wrapper<F>) noexcept;

    template<class F, class A> void assign(F&&, const A&);
    //...
};

There is a problem.

void foo();
void foo(int);

std::function<void()> fn;
fn = foo; //Error! 'void foo()'? or 'void foo(int)'?

Why not provide a method for std::function to fix the problem? like this.

function& operator=(R(ArgTypes...));

Thanks.
Jinhao




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