[Help-gsl] Householder transformation

[Ali kia]

Hi,
I want to zero all items below a11 with gel. I have this code, but I don't know 
how to use gel functions? 
(http://www.inference.phy.cam.ac.uk/pjc51/local/gsl/manual/gsl-ref_13.html#SEC228)

#include <iostream>#include <math.h>#include <stdio.h>#include 
<gsl/gsl_matrix.h>#include <gsl/gsl_blas.h>
const Int DIM=4;
intmain (void){  size_t i,j;
  gsl_matrix *m = gsl_matrix_alloc (DIM, DIM);
  for (i = 0; i < DIM; i++)    for (j = 0; j < DIM; j++)      gsl_matrix_set 
(m, i, j,4);
  for (i = 0; i < DIM; i++){    for (j = 0; j < DIM; j++){      
std::cout<<gsl_matrix_get(m, i, j);
        }       std::cout<<std::endl;}
  gsl_matrix_free (m);
  return 0;}
Best regards,A.K