function value = i4vec_norm_l0 ( n, a )

%*****************************************************************************80
%
%% I4VEC_NORM_L0 returns the l0 "norm" of an I4VEC.
%
%  Discussion:
%
%    An I4VEC is a vector of I4's.
%
%    The l0 "norm" simply counts the number of nonzero entries in the vector.
%    It is not a true norm, but has some similarities to one.  It is useful
%    in the study of compressive sensing.
%
%  Licensing:
%
%    This code is distributed under the GNU LGPL license.
%
%  Modified:
%
%    01 June 2012
%
%  Author:
%
%    John Burkardt
%
%  Parameters:
%
%    Input, integer N, the number of entries in the vector.
%
%    Input, integer A(N), the vector.
%
%    Output, integer I4VEC_NORM_L0, the value of the norm.
%
  value = sum ( a(1:n) ~= 0 );

  return
end