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) 2007-2022 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} =} strjoin (@var{cstr})
## @deftypefnx {} {@var{str} =} strjoin (@var{cstr}, @var{delimiter})
## Join the elements of the cell string array, @var{cstr}, into a single
## string.
##
## If no @var{delimiter} is specified, the elements of @var{cstr} are
## separated by a space.
##
## If @var{delimiter} is specified as a string, the cell string array is
## joined using the string.  Escape sequences are supported.
##
## If @var{delimiter} is a cell string array whose length is one less than
## @var{cstr}, then the elements of @var{cstr} are joined by interleaving the
## cell string elements of @var{delimiter}.  Escape sequences are not
## supported.
##
## @example
## @group
## strjoin (@{'Octave','Scilab','Lush','Yorick'@}, '*')
##       @result{} 'Octave*Scilab*Lush*Yorick'
## @end group
## @end example
## @seealso{strsplit}
## @end deftypefn

function rval = strjoin (cstr, delimiter = " ")

  if (nargin < 1)
    print_usage ();
  elseif (! (iscellstr (cstr) && (ischar (delimiter) || iscellstr (delimiter))))
    print_usage ();
  endif

  if (numel (cstr) == 1)
    rval = cstr{1};
    return;
  endif

  if (ischar (delimiter))
    delimiter = do_string_escapes (delimiter);
    delimiter = {delimiter};
  endif

  num = numel (cstr);
  if (numel (delimiter) == 1 && num > 1)
    delimiter = repmat (delimiter, 1, num);
    delimiter(end) = {""};
  elseif (num > 0 && numel (delimiter) != num - 1)
    error ("Octave:strjoin:cellstring_delimiter_mismatch",
      "strjoin: the number of delimiters does not match the number of strings");
  else
    delimiter(end+1) = {""};
  endif

  if (num == 0)
    rval = "";
  else
    rval = [[cstr(:).'; delimiter(:).']{:}];
  endif

endfunction


%!assert (strjoin ({"hello"}, "-"), "hello")
%!assert (strjoin ({"hello", "world"}), "hello world")
%!assert (strjoin ({"Octave", "Scilab", "Lush", "Yorick"}, "*"),
%!  "Octave*Scilab*Lush*Yorick")
%!assert (strjoin ({"space", "comma", "dash", "semicolon", "done"},
%!  {" ", ",", "-", ";"}), "space comma,dash-semicolon;done")
%!assert (strjoin ({'Octave','Scilab'},'\n'), "Octave\nScilab")
%!assert (strjoin ({'Octave','Scilab'},{'\n'}), "Octave\\nScilab")
%!assert (strjoin ({},'foo'), "")