gistfile1.cpp

#include <map>
#include <vector>
#include <string>
#include <future>
#include <numeric>
#include <iterator>
#include <boost/lexical_cast.hpp>

using namespace std;
using boost::lexical_cast;

typedef map<string, string> object;

vector<object> objects = { 
    {{"user", "kyle"}, {"amount", "42"}},
    {{"user", "kyle"}, {"amount", "1"}},
    {{"user",  "andy"}, {"amount", "0"}}
};

namespace arg { 

    template <typename T, typename Pred>
    vector<T> remove_copy_if(vector<T> t, Pred f) 
    {
        vector<T> res;
        std::remove_copy_if(begin(t), end(t), back_inserter(res), f);
        return res;
    }

    template <typename T, typename F>
    auto transform(vector<T> t, F f) -> vector<decltype(f(T()))>
    {
        vector<decltype(f(T()))> res;
        std::transform(begin(t), end(t), back_inserter(res), f);
        return res;
    }

    template <typename T>
    int accumulate(vector<T> t) 
    {
        return std::accumulate(begin(t), end(t), 0);
    }

}

int main(void) { 
    cout << arg::accumulate(
                arg::transform(
                    arg::remove_copy_if(objects,[](object o){ return o["user"] != "kyle"; }),
                    [](object o) { return lexical_cast<int>(o["amount"]); })) << endl;
    return 0;
}