Exception for 2frac (problem 3.3.1)

Math

\[\frac{1}{x + 1} - \frac{1}{x}\]

C

double code(double x) {
	return ((double) (((double) (1.0 / ((double) (x + 1.0)))) - ((double) (1.0 / x))));
}

Reproduce

herbie shell --seed 2020148 
(FPCore (x)
  :name "2frac (problem 3.3.1)"
  :precision binary64
  (- (/ 1.0 (+ x 1.0)) (/ 1.0 x)))