#include <iostream>
#include <array>
#include <functional>

template <class T, int array_size, class func_t>
constexpr std::array<T, array_size> from_fn(func_t f) {

    std::array<T, array_size> arr{};

    for (int i = 0; i < array_size; i++) {

        arr[i] = f(i);
    }

    return arr;
}


constexpr auto a = from_fn<int, 10>([](auto x) {return x*25;});
constexpr auto b = from_fn<double, 5>([](auto x) {return 0.1*x;});

int main() {

    std::cout << a.at(5) << std::endl;
    std::cout << b.at(2) << std::endl;

    return 0;
}