利用多态实现std::function

#ifndef PINK_FUNCTION_H
#define PINK_FUNCTION_H


template<typename R, class... Arg0>
class function{
public:
    function(R(*fun)(Arg0...)) {
        __calltable<R(*)(Arg0...)>* table = new __calltable<R(*)(Arg0...)>(fun);
        this->base = (__callbase*)table;
    }
    R operator()(Arg0... arg) {
        return (*base)(arg...);
    }
    ~function() {
        if (base) delete base;
    }
    
private:
//base class
class __callbase{
public:
    virtual R operator()(Arg0... arg) =  0;
    virtual ~__callbase() {};
};

//define class
template<typename F>
class __calltable : __callbase{
public:
    __calltable(F fun) {
        fun_ = fun;
    };
    virtual R operator()(Arg0... arg) {
        return fun_(arg...);
    }
    virtual ~__calltable() {};
private:
    F fun_;
};
__callbase* base;
};
#endif

用法：

#include<stdio.h>
#include"mfunction.h"

int main() {
   function<int, char, char> f([](char b, char c ){
       printf("%d%d\n",b, c);
       return 10;
   });
   f('c', 'a');
}