list comprehensions for C++

vector_comprehension.hpp

// Python style list comprehensions for C++.
// Example: multiply all elements of vector literal by 2.
//
// auto vec_doubled = VFOR(std::vector<int>({1,2,3}), x, x * 2);
// 
// vec_squared is now equal to std::vector<int>({1,4,6})

#include <vector>
#include <type_traits>

template <typename T, typename Function,
          typename ResultType = std::vector<typename std::result_of<Function(const T&)>::type> >
ResultType vector_comprehension(const std::vector<T>& in_vec,
                                    Function func) {
    ResultType result;
    for (auto& elem : in_vec) {
        result.push_back(func(elem));
    }
    return result;
}

template <typename T>
struct Get: T {};

// Macros apparently don't like C++11 style literals unless wrapped in something (in G++ at least).
// So you can't do VFOR({1,2,3}, x, x * x), you have to do 
#define VFOR(coll, var, expr)                                           \
    vector_comprehension<Get<std::remove_reference<decltype(coll)>::type>::value_type> \
    ((coll), [&](Get<std::remove_reference<decltype(coll)>::type>::const_reference var) { return (expr);})