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## Copyright (C) 2021 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
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## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
## GNU General Public License for more details.
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## You should have received a copy of the GNU General Public License
## along with Octave; see the file COPYING.  If not, see
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########################################################################

## -*- texinfo -*-
## @deftypefn  {} {@var{r} =} convertStringsToChars (@var{a})
## @deftypefnx {} {[@var{r1}, @var{r2}, @dots{}, @var{rn}] =} convertStringsToChars (@var{a1}, @var{a2}, @dots{}, @var{an})
## Convert arrays of string objects into characters arrays.
##
## A string scalar @var{a} is converted into a character row vector @var{r}
## while a string array @var{a} is converted into a cell array of character row
## vectors. Other variables types are left unchanged.
##
## This function can be used for compatibility with functions that make use of
## characters arrays or cell arrays of strings as input arguments but are not
## compatible with string objects.  For example:
##
## @example
## @group
## function example_function (a, b)
##   [a, b] = convertStringsToChars (a, b);
##   ...
## endfunction
## @end group
## @end example
## or
## @example
## @group
## function varargout = example_function (varargin)
##   [vararging{1:nargin}] = convertStringsToChars (varargin{:});
##   ...
## endfunction
## @end group
## @end example
##
## @seealso{convertContainedStringsToChars, convertCharsToStrings}
## @end deftypefn

function varargout = convertStringsToChars (varargin)

  if (! (nargin < 2 && ! nargout) && (nargin != nargout))
    error ("Mismatch between number of input and output arguments.");
  endif

  varargout = varargin;

  for i = 1:numel(varargin)
    if (isstring (varargin{i}))
      if (isscalar (varargin{i}))
        varargout{i} = char (varargin{i});
      else
        varargout{i} = cellstr (varargin{i});
      endif
    endif
  endfor

endfunction


%!test
%! convertStringsToChars;
%! convertStringsToChars ("Octave");

%!test
%! r = convertStringsToChars ("Octave");
%! assert (ischar (r));
%! [r1, r2] = convertStringsToChars ("GNU", "Octave");
%! assert (ischar (r1));
%! assert (ischar (r2));

%!test
%! r = convertStringsToChars ("");
%! assert (ischar (r))
%! assert (size (r), [0, 0])

%!test
%! a = ["GNU", "Octave"];
%! r = convertStringsToChars (a);
## FIXME: when string arrays are implemented, this should be uncommented.
#%! assert (iscellstr (r))

%!test
%! r = convertStringsToChars ("Octave");
%! assert (ischar (r))
%! assert (r, 'Octave')

%!test
%! [r1, r2] = convertStringsToChars ("Octave", pi);
%! assert (ischar (r1))
%! assert (r1, 'Octave')
%! assert (r2, pi)

%!test
%! [r1, r2, r3, r4] = convertStringsToChars ({"GNU"}, "Octave", 'pi', pi);
%! assert ({r1, r2, r3, r4}, {{"GNU"}, 'Octave', 'pi', pi})

%!error r = convertStringsToChars;
%!error r = convertStringsToChars ("GNU", "Octave");
%!error [r1, r2] = convertStringsToChars ("Octave");
