IIR

#include <iostream>
#include <vector>
#include <deque>
#include <numeric>

int main()
{
    std::vector<double> b = { 0.0089, -0.0045, -0.0045, 0.0089 };
    std::vector<double> a = { 1, 2.5641, -2.2185, 0.6456 };

    std::deque<double> d( std::max(a.size(), b.size()) );

    for (int i = 0; i < 150; ++i)
    {
        d.push_front(1.0);
        d.pop_back();
        d[0] = std::inner_product(begin(a), end(a), begin(d), 0.0);
        double y = std::inner_product(begin(b), end(b), begin(d), 0.0);
        std::cout << y << std::endl;
    }
}