boost封裝函數指針

boost封裝了函數指針，函數指針使用起來更加簡便：

#include <iostream>
#include "boost/function.hpp"

double add(double a, double b)
{
        std::cout<<a+b<<std::endl;
        return (a + b); 
}
double del(double a, double b)
{
        std::cout<<(a - b)<<std::endl;
        return (a - b); 
}
int main()
{
        boost::function<double (double, double)> func[2]={add, del};
        (*func)(1,0);
        (* (func+1))(4,2);
        return 0;

}