函数对象好例子

#include <iostream>
#include <string>
#include <vector>
#include <cassert>
#include <typeinfo>
#include <algorithm>
#include <boost/any.hpp>
typedef boost::any cell_t;
typedef std::vector<cell_t> db_row_t;
db_row_t get_row(const char *) {
    db_row_t row;
    row.push_back(10);
    row.push_back(10.1f);
    row.push_back(std::string("hello world!"));
    return row;
}
struct db_sum {
public:
    explicit db_sum(double &sum) : sum_(sum) {
    }   
    void operator () (const cell_t &value) {
        const std::type_info &ti = value.type();
        if (typeid(int) == ti) {
            sum_ += boost::any_cast<int>(value);
        }   
        else if (typeid(float) == ti) {
            sum_ += boost::any_cast<float>(value);
        }   
    }   
private:
    double &sum_;
};
int main() {
    db_row_t row = get_row("");
    double res = 0.0;
    std::for_each(begin(row), end(row), db_sum(res));
    std::cout << res << std::endl;

    return 0;
}