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##
## Copyright (C) 2017-2024 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.
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## 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
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########################################################################

## -*- texinfo -*-
## @deftypefn {} {@var{tf} =} isstring (@var{s})
## Return true if @var{s} is a string array.
##
## A string array is a data type that stores strings (row vectors of
## characters) at each element in the array.  It is distinct from character
## arrays which are N-dimensional arrays where each element is a single 1x1
## character.  It is also distinct from cell arrays of strings which store
## strings at each element, but use cell indexing @samp{@{@}} to access
## elements rather than string arrays which use ordinary array indexing
## @samp{()}.
##
## Programming Note: Octave does not yet implement string arrays so this
## function will always return false.
## @seealso{ischar, iscellstr, isfloat, isinteger, islogical, isnumeric, isa}
## @end deftypefn

function tf = isstring (s)

  if (nargin < 1)
    print_usage ();
  endif

  tf = isa (s, 'string');

endfunction


%!assert (isstring ([]), false)
%!assert (isstring (1), false)
%!assert (isstring ('a'), false)
## FIXME: when string arrays are implemented, this should return true.
%!#assert (isstring ("b"), true)
%!assert (isstring ({'a'}), false)
%!assert (isstring ({"b"}), false)

%!error <Invalid call> isstring ()