\[0.0 \lt x \lt 1 \land y \lt 1\]

\[\frac{\left(x - y\right) \cdot \left(x + y\right)}{x \cdot x + y \cdot y}\]

\frac{\left(x - y\right) \cdot \left(x + y\right)}{x \cdot x + y \cdot y}

double code(double x, double y) {
	return ((double) (((double) (((double) (x - y)) * ((double) (x + y)))) / ((double) (((double) (x * x)) + ((double) (y * y))))));
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2020169 
(FPCore (x y)
  :name "Kahan p9 Example"
  :precision binary64
  :pre (and (< 0.0 x 1.0) (< y 1.0))

  :herbie-target
  (if (< 0.5 (fabs (/ x y)) 2.0) (/ (* (- x y) (+ x y)) (+ (* x x) (* y y))) (- 1.0 (/ 2.0 (+ 1.0 (* (/ x y) (/ x y))))))

  (/ (* (- x y) (+ x y)) (+ (* x x) (* y y))))

Backtrace

match-define: no matching clause for '(== branch373 -3.290469609850284e+158)		L	C
match:error	/opt/racket-7.5/collects/racket/match/runtime.rkt	24	0
program-body	/data/pavpan/nightlies/herbie/ival-find-range/src/programs.rkt	25	0
(unnamed)	/opt/racket-7.5/collects/racket/contract/private/arrow-higher-order.rkt	379	33
prepare-points	/data/pavpan/nightlies/herbie/ival-find-range/src/points.rkt	130	0
pred	/data/pavpan/nightlies/herbie/ival-find-range/src/core/regimes.rkt	204	4
.../more-scheme.rkt:261:28	unknown
for-loop	/data/pavpan/nightlies/herbie/ival-find-range/src/core/regimes.rkt	240	3
sindices->spoints	/data/pavpan/nightlies/herbie/ival-find-range/src/core/regimes.rkt	194	0
f37	unknown
get-final-combination	/data/pavpan/nightlies/herbie/ival-find-range/src/mainloop.rkt	389	0
.../more-scheme.rkt:261:28	unknown
run	/opt/racket-7.5/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk16	/opt/racket-7.5/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.5/collects/racket/private/more-scheme.rkt	261	28

Reproduce

herbie shell --seed 2020169 
(FPCore (x y)
  :name "Kahan p9 Example"
  :precision binary64
  :pre (and (< 0.0 x 1.0) (< y 1.0))

  :herbie-target
  (if (< 0.5 (fabs (/ x y)) 2.0) (/ (* (- x y) (+ x y)) (+ (* x x) (* y y))) (- 1.0 (/ 2.0 (+ 1.0 (* (/ x y) (/ x y))))))

  (/ (* (- x y) (+ x y)) (+ (* x x) (* y y))))