\[0 \lt x \lt 1 \land y \lt 1\]

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

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

double f(double x, double y) {
        double r2527126 = x;
        double r2527127 = y;
        double r2527128 = r2527126 - r2527127;
        double r2527129 = r2527126 + r2527127;
        double r2527130 = r2527128 * r2527129;
        double r2527131 = r2527126 * r2527126;
        double r2527132 = r2527127 * r2527127;
        double r2527133 = r2527131 + r2527132;
        double r2527134 = r2527130 / r2527133;
        return r2527134;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019139 
(FPCore (x y)
  :name "Kahan p9 Example"
  :pre (and (< 0 x 1) (< y 1))

  :herbie-target
  (if (< 0.5 (fabs (/ x y)) 2) (/ (* (- x y) (+ x y)) (+ (* x x) (* y y))) (- 1 (/ 2 (+ 1 (* (/ x y) (/ x y))))))

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

Backtrace

argmin: contract violation expected: (and/c list? (not/c empty?)) given: '() argument position: 2nd other arguments...: #<procedure:composed>		L	C
argmin	/opt/racket-7.0/collects/racket/list.rkt	765	0
infer-splitpoints	/data/pavpan/nightlies/herbie/develop/src/core/regimes.rkt	34	0
get-final-combination	/data/pavpan/nightlies/herbie/develop/src/mainloop.rkt	361	0
(unnamed)	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	261	28
run	/opt/racket-7.0/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk16	/opt/racket-7.0/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	261	28