void iir_mem2(float *x, float *den, float *y, int N, int ord, float *mem)
void iir_mem2(float *x, spx_coef_t *den, float *y, int N, int ord, spx_mem_t *mem)
void iir_mem2(float *x, float *den, float *y, int N, int ord, float *mem){   int i,j;   for (i=0;i<N;i++)   {      y[i] = x[i] + mem[0];      for (j=0;j<ord-1;j++)      {         mem[j] = mem[j+1] - den[j+1]*y[i];      }      mem[ord-1] = - den[ord]*y[i];   }}