function ok = chkstr(str,opt)


% CHKSTR  Checks Input for String
%
%  ok = chkstr(str,Option)
%
%  Option ~= 0 ==> only true for nonempty Strings
%
%   default:   Option == 0  (true for empty Strings)
%

 
if nargin < 2
   opt = 0;
end

ok = ( strcmp( class(str) , 'char' )      & ...
       ( prod(size(str)) == size(str,2) ) & ...
       ( isequal(opt,0) | ~isempty(str) )         );

