#include <iostream>
#include <string>
#include <vector>

template <typename T>
using identity = T;

template <typename T>
using reference = T&;

template <template <class> typename F, template <template <class> class> class S>
struct soa_wrapper : S<F> {
    S<reference> operator[](std::size_t i) {
        auto& [x, y, activation, identifier] = *this;
        return {x[i], y[i], activation[i], identifier[i]};
    }
};

struct Point2D { double x, y; };

template<template <class> class F>
struct S {
    F<int> x, y;
    F<Point2D> activation;
    F<std::string> identifier;

    int abs2() const { return x * x + y * y; }  // not defined for std::vector<int>
    int& getX() { return x; }
    void setX(int x_new) { x = x_new; }
};

int main() {
    soa_wrapper<std::vector, S> my_array;
    my_array.x = {0, 1, 2};
    my_array.y = {0, 1, 2};
    my_array.activation = {{0, 1}, {2, 3}, {4, 5}};
    my_array.identifier = {"bla", "foo", "bar"};

    my_array[1].setX(10);
    my_array[1].getX();
    for (int i = 0; i < 3; ++i) std::cout << my_array[i].abs2() << std::endl;

    return 0;
}