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## -*- texinfo -*-
## @deftypefn {} {@var{y} =} reallog (@var{x})
## Return the real-valued natural logarithm of each element of @var{x}.
##
## If any element results in a complex return value @code{reallog} aborts and
## issues an error.
## @seealso{log, realpow, realsqrt}
## @end deftypefn

function y = reallog (x)

  if (nargin < 1)
    print_usage ();
  elseif (iscomplex (x) || any (x(:) < 0))
    error ("reallog: produced complex result");
  else
    y = log (x);
  endif

endfunction


%!assert (reallog (1:5), log (1:5))
%!test
%! x = rand (10, 10);
%! assert (reallog (x), log (x));

%!error <Invalid call> reallog ()
%!error <produced complex result> reallog (2i)
%!error <produced complex result> reallog (-1)
