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c++c++11std-functionstdbind

omit std::placeholders in std::bind


To create std::function, here is what I do:-

std::function<void(int,int,int)> f =
    std::bind(&B::fb,this,
        std::placeholders::_1,
        std::placeholders::_2,
        std::placeholders::_3
    );  

void B::fb(int x,int k,int j){} //example

It is obvious that B::fb receive three parameters.
To increase readability & maintainability, I wish I could call this instead :-

std::function<void(int,int,int)> f=std::bind(&B::fb,this);  //omit _1 _2 _3

Question
Are there any features in C++ that enable omitting the placeholders?
It should call _1,_2, ..., in orders automatically.

I have googled "omit placeholders c++" but not find any clue.


Solution

  • You may create functions helper (those ones are C++14):

    template <class C, typename Ret, typename ... Ts>
    std::function<Ret(Ts...)> bind_this(C* c, Ret (C::*m)(Ts...))
    {
        return [=](auto&&... args) { return (c->*m)(std::forward<decltype(args)>(args)...); };
    }
    
    template <class C, typename Ret, typename ... Ts>
    std::function<Ret(Ts...)> bind_this(const C* c, Ret (C::*m)(Ts...) const)
    {
        return [=](auto&&... args) { return (c->*m)(std::forward<decltype(args)>(args)...); };
    }
    

    and then just write

    std::function<void(int, int, int)> f = bind_this(this, &B::fb);