class delay {
    double *m_buf;
    int m_len,m_pos;
public:
    delay(int len) { m_len=len; m_buf=(double*)calloc(sizeof(double),len); m_pos=0; }
    ~delay() { free(m_buf); }
    double process(double in) {
        double ret=m_buf[m_pos];
        m_buf[m_pos]=in;
        if (++m_pos>=m_len) m_pos=0;
        return ret;
    }
};