doc: Ensure documentation lists output argument when it exists for all m-files. For new users of Octave it is best to show explicit calling forms in the documentation and to show a return argument when it exists. * bp-table.cc, shift.m, accumarray.m, accumdim.m, bincoeff.m, bitcmp.m, bitget.m, bitset.m, blkdiag.m, celldisp.m, cplxpair.m, dblquad.m, flip.m, fliplr.m, flipud.m, idivide.m, int2str.m, interpft.m, logspace.m, num2str.m, polyarea.m, postpad.m, prepad.m, randi.m, repmat.m, rng.m, rot90.m, rotdim.m, structfun.m, triplequad.m, uibuttongroup.m, uicontrol.m, uipanel.m, uipushtool.m, uitoggletool.m, uitoolbar.m, waitforbuttonpress.m, help.m, __additional_help_message__.m, hsv.m, im2double.m, im2frame.m, javachk.m, usejava.m, argnames.m, char.m, formula.m, inline.m, __vectorize__.m, findstr.m, flipdim.m, strmatch.m, vectorize.m, commutation_matrix.m, cond.m, cross.m, duplication_matrix.m, expm.m, orth.m, rank.m, rref.m, trace.m, vech.m, cast.m, compare_versions.m, delete.m, dir.m, fileattrib.m, grabcode.m, gunzip.m, inputname.m, license.m, list_primes.m, ls.m, mexext.m, movefile.m, namelengthmax.m, nargoutchk.m, nthargout.m, substruct.m, swapbytes.m, ver.m, verLessThan.m, what.m, fminunc.m, fsolve.m, fzero.m, optimget.m, __fdjac__.m, matlabroot.m, savepath.m, campos.m, camroll.m, camtarget.m, camup.m, camva.m, camzoom.m, clabel.m, diffuse.m, legend.m, orient.m, rticks.m, specular.m, thetaticks.m, xlim.m, xtickangle.m, xticklabels.m, xticks.m, ylim.m, ytickangle.m, yticklabels.m, yticks.m, zlim.m, ztickangle.m, zticklabels.m, zticks.m, ellipsoid.m, isocolors.m, isonormals.m, stairs.m, surfnorm.m, __actual_axis_position__.m, __pltopt__.m, close.m, graphics_toolkit.m, pan.m, print.m, printd.m, __ghostscript__.m, __gnuplot_print__.m, __opengl_print__.m, rotate3d.m, subplot.m, zoom.m, compan.m, conv.m, poly.m, polyaffine.m, polyder.m, polyint.m, polyout.m, polyreduce.m, polyvalm.m, roots.m, prefdir.m, prefsfile.m, profexplore.m, profexport.m, profshow.m, powerset.m, unique.m, arch_rnd.m, arma_rnd.m, autoreg_matrix.m, bartlett.m, blackman.m, detrend.m, durbinlevinson.m, fftconv.m, fftfilt.m, fftshift.m, fractdiff.m, hamming.m, hanning.m, hurst.m, ifftshift.m, rectangle_lw.m, rectangle_sw.m, triangle_lw.m, sinc.m, sinetone.m, sinewave.m, spectral_adf.m, spectral_xdf.m, spencer.m, ilu.m, __sprand__.m, sprand.m, sprandn.m, sprandsym.m, treelayout.m, beta.m, betainc.m, betaincinv.m, betaln.m, cosint.m, expint.m, factorial.m, gammainc.m, gammaincinv.m, lcm.m, nthroot.m, perms.m, reallog.m, realpow.m, realsqrt.m, sinint.m, hadamard.m, hankel.m, hilb.m, invhilb.m, magic.m, pascal.m, rosser.m, toeplitz.m, vander.m, wilkinson.m, center.m, corr.m, cov.m, discrete_cdf.m, discrete_inv.m, discrete_pdf.m, discrete_rnd.m, empirical_cdf.m, empirical_inv.m, empirical_pdf.m, empirical_rnd.m, kendall.m, kurtosis.m, mad.m, mean.m, meansq.m, median.m, mode.m, moment.m, range.m, ranks.m, run_count.m, skewness.m, spearman.m, statistics.m, std.m, base2dec.m, bin2dec.m, blanks.m, cstrcat.m, deblank.m, dec2base.m, dec2bin.m, dec2hex.m, hex2dec.m, index.m, regexptranslate.m, rindex.m, strcat.m, strjust.m, strtrim.m, strtrunc.m, substr.m, untabify.m, __have_feature__.m, __prog_output_assert__.m, __run_test_suite__.m, example.m, fail.m, asctime.m, calendar.m, ctime.m, date.m, etime.m: Add return arguments to @deftypefn macros where they were missing. Rename variables in functions (particularly generic "retval") to match documentation. Rename some return variables for (hopefully) better clarity (e.g., 'ax' to 'hax' to indicate it is a graphics handle to an axes object).

########################################################################
##
## Copyright (C) 2010-2022 The Octave Project Developers
##
## See the file COPYRIGHT.md in the top-level directory of this
## distribution or <https://octave.org/copyright/>.
##
## This file is part of Octave.
##
## Octave is free software: you can redistribute it and/or modify it
## under the terms of the GNU General Public License as published by
## the Free Software Foundation, either version 3 of the License, or
## (at your option) any later version.
##
## Octave is distributed in the hope that it will be useful, but
## WITHOUT ANY WARRANTY; without even the implied warranty of
## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
##
## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, see
## <https://www.gnu.org/licenses/>.
##
########################################################################

## -*- texinfo -*-
## @deftypefn  {} {@var{str} =} untabify (@var{t})
## @deftypefnx {} {@var{str} =} untabify (@var{t}, @var{tw})
## @deftypefnx {} {@var{str} =} untabify (@var{t}, @var{tw}, @var{deblank})
## Replace TAB characters in @var{t} with spaces.
##
## The input, @var{t}, may be either a 2-D character array, or a cell array of
## character strings.  The output is the same class as the input.
##
## The tab width is specified by @var{tw}, and defaults to eight.
##
## If the optional argument @var{deblank} is true, then the spaces will be
## removed from the end of the character data.
##
## The following example reads a file and writes an untabified version of the
## same file with trailing spaces stripped.
##
## @example
## @group
## fid = fopen ("tabbed_script.m");
## text = char (fread (fid, "uchar")');
## fclose (fid);
## fid = fopen ("untabified_script.m", "w");
## text = untabify (strsplit (text, "\n"), 8, true);
## fprintf (fid, "%s\n", text@{:@});
## fclose (fid);
## @end group
## @end example
##
## @seealso{strjust, strsplit, deblank}
## @end deftypefn

function str = untabify (t, tw = 8, deblank_arg = false)

  if (nargin < 1)
    print_usage ();
  elseif (! (ischar (t) || iscellstr (t)))
    error ("untabify: T must be a string or cellstring");
  endif

  if (ischar (t))
    str = replace_tabs (t, tw);
  else
    str = cellfun (@replace_tabs, t, {tw}, "uniformoutput", false);
  endif

  if (deblank_arg)
    str = deblank (str);
  endif

endfunction

function s = replace_tabs (t, tw)

  if (ndims (t) != 2)
    error ("untabify: character strings to untabify must have 2 dimensions");
  endif

  if (isempty (t))
    s = t;
  else
    nr = rows (t);
    sc = cell (nr, 1);
    for j = 1:nr
      n = 1:numel (t(j,:));
      m = find (t(j,:) == "\t");
      t(j,m) = " ";
      for i = 1:numel (m)
        k = tw * ceil (n(m(i)) / tw);
        dn = k - n(m(i));
        n(m(i):end) += dn;
      endfor
      sc{j} = blanks (n(end));
      sc{j}(n) = t(j,:);
    endfor
    s = char (sc);
  endif

endfunction


%!test
%! s = untabify ("\thello\t");
%! assert (s, [blanks(8) "hello" blanks(3)]);

%!test
%! s = untabify ("\thello\t", 2);
%! assert (s, [blanks(2) "hello" blanks(1)]);

%!test
%! s = untabify ("\thello\t", 4, true);
%! assert (s, [blanks(4) "hello"]);

%!assert (isempty (untabify ("")))

%!test
%! s = char (randi ([97 97+25], 3, 3));
%! assert (untabify (s), char (untabify (cellstr (s))));

## Test input validation
%!error <Invalid call> untabify ()
%!error <must be a string> untabify (1)