function [tf,txt] = isText(txt, varargin)

%ISTEXT True for an array containing text values

%   TF = ISTEXT(TXT) returns true if TXT is an array containing text, i.e. TXT is

%      * a string array

%      * a 1xN character vector

%      * the 0x0 char array ''

%      * a cell array containing char row vectors or ''

%   and false otherwise. In particular, ISTEXT returns false if TXT is a cell

%   array that contains [] in any element, or if TXT is not a row. Note that

%   the latter is different than how ISCELLSTR behaves.

%

%   TF = ISTEXT(TXT,FORBIDCHAR), when FORBIDCHAR is true, returns true only when

%   TXT is a string array or a cell array containing char row vectors, and false

%   otherwise. In particular, ISTEXT(TXT,TRUE) returns false if TXT is a char

%   row vector. This supports pre-string syntaxes where a function requires a

%   cellstr, and does not accept a raw char row.

%

%   TF = ISTEXT(S,FORBIDCHAR,FALSE) returns true only if TXT contains

%   non-empty, non-missing text, i.e. TXT is

%      * a string array whose elements not equal to "", all whitespace, or <missing>

%      * a 1xN character vector for N > 0, not all whitespace

%      * a cell array containing non-empty, non-missing char row vectors

%

%   When TXT is a char row vector, [TF,TXT] = ISTEXT(TXT,...) also returns

%   {TXT}.  If TXT is a string array or cell array containing char row vectors,

%   ISTEXT returns TXT itself.  Otherwise, ISTEXT returns a 0x0 cell or string

%   array in TXT.

%

%   See also MATLAB.INTERNAL.DATATYPES.ISSCALARTEXT, ISSPACE, STRINGS.

%   Copyright 2017-2018 The MathWorks, Inc.

import matlab.internal.datatypes.isCharStrings

import matlab.internal.datatypes.anyIsAllWhitespace

narginchk(1,3) 

if isstring(txt) 

    % FORBIDCHAR has no impact on string inputs

    % ALLOWEMPTYORMISSING needs to be checked only if false

    if nargin < 3 || varargin{2}

        tf = true;

    else  % nargin == 3 && ~varargin{2}

        % Require all strings to be non-empty and non-missing.

        if any(ismissing(txt))

            tf = false;

            if nargout > 1

                txt(1:end) = [];

                txt = reshape(txt,0,0); % faster than string.empty

            end

        elseif anyIsAllWhitespace(txt)

            tf = false;

            if nargout > 1

                txt(1:end) = [];

                txt = reshape(txt,0,0); 

            end

        else

            tf = true;

        end

    end    

else 

    if nargout < 2 

        tf = isCharStrings(txt, varargin{:}); 

    else

        [tf,txt] = isCharStrings(txt, varargin{:});

    end 

end