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## -*- texinfo -*-
## @deftypefn  {} {@var{val} =} sparse_auto_mutate ()
## @deftypefnx {} {@var{old_val} =} sparse_auto_mutate (@var{new_val})
## @deftypefnx {} {@var{old_val} =} sparse_auto_mutate (@var{new_val}, "local")
##
## @code{sparse_auto_mutate} is deprecated and will be removed in Octave
## version 9.  Use @code{optimize_diagonal_matrix} instead.
##
## Query or set whether storing diagonal matrices in a special space-efficient
## format is disabled.
##
## The default value is false.  If this option is set to true, Octave will
## store ranges as full matrices.
##
## When called from inside a function with the @qcode{"local"} option, the
## setting is changed locally for the function and any subroutines it calls.
## The original setting is restored when exiting the function.
## @seealso{sparse_auto_mutate, disable_permutation_matrix}
## @end deftypefn

## FIXME: DEPRECATED: Remove in version 10.

function retval = sparse_auto_mutate (val, opt)

  persistent warned = false;
  if (! warned)
    warned = true;
    warning ("Octave:deprecated-function",
             "sparse_auto_mutate is obsolete, has no effect, and will be removed from a future version of Octave\n");
  endif

  if (nargin == 0 || nargout > 0)
    ## Always false now.
    retval = false;
    return;
  endif

  if (nargin == 2)
    if (! (ischar (opt) && strcmp (opt, "local")))
      error ('sparse_auto_mutate: second argument must be "local"');
    endif
    nargin = 1;
  endif

  ## Don't bother warning that "local" is invalid outside of a
  ## function.

  if (nargin > 1)
    print_usage ();
  endif

  if (! islogical (val))
    error ("sparse_auto_mutate: argument must be a logical value");
  endif

endfunction