simpsau0( f, range, oldstep, epsi)

          %function interne
          function intr = simpsau0( f, range, oldstep, epsi)

          a = range(1); 
          b = range(2); 
          mil = (b+a).*0.5;
          h = (mil-a)./6.0;
          fmil = feval(f, mil);
          s1 = (feval(f,a) + 4.0.*feval(f,(a+mil).*0.5) + fmil).*h;
          s2 = (fmil + 4.0.*feval(f,(mil+b).*0.5) + feval(f,b)).*h;
          err = abs(s1+s2-oldstep);
          if err>=15.0.*epsi.*(b-a)
            range = [a, mil];
            s1 = simpsau0(f, range, s1, epsi);
            range = [mil, b];
            s2 = simpsau0(f, range, s2, epsi);
          end;
          intr = s1 + s2;