double func1(std::map<std::string, double> arr)
{
    dydt = arr["one"] * 3.0 - arr["two"];
    return dydt;
}

double func2(std::map<std::string, double> arr)
{
    dydt = 1 / arr["three"] + 3.0 * arr["two"];
    return dydt;
}

double solver(std::vector<std::function<double(std::map<char, double>) &funcs, std::map<std::string, double> inputs)
{
    double res;
    std::vector<double> data;
    for (int i = 0; i < funcs.size(); i++)
    {
        // - The ODE solver is not shown in this example,
        //   but it highlights the general intent
        res = funcs[i](inputs);
        data.push_back(res);
    }
    return data;
}

int main()
{
    std::map<std::string, double> inputs;
    inputs["one"] = 1.0;
    inputs["two"] = 2.0;
    inputs["three"] = 3.0;
    inputs["four"] = 4.0;

    // The line of code below does not work
    std::vector<std::function<double(std::map<char, double>)>> funcs = {func1, func2};
    std::vector<double> dat;

    // - Due to the fact that the array of funcs does not work,
    //  this function call also does not work
    dat = solver(funcs, inputs);
    return 0;
}