| DEFUN (isnull, args,,"-*- texinfo -*-\n\
@deftypefn {Built-in Function} {} isnull (@var{x})\n\
Return true if @var{x} is a special null matrix, string, or single quoted\n\
string. Indexed assignment with such a value on the right-hand side should\n\
delete array elements. This function should be used when overloading\n\
indexed assignment for user-defined classes instead of @code{isempty}, to\n\
distinguish the cases:\n\
@table @asis\n\
@item @code{A(I) = []}\n\
This should delete elements if @code{I} is nonempty.\n\
\n\
@item @code{X = []; A(I) = X}\n\
This should give an error if @code{I} is nonempty.\n\
@end table\n\
@seealso{isempty, isindex}\n\
@end deftypefn") |