Exception for Complex division, imag part

Math

\[\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d}\]

C

double f(double a, double b, double c, double d) {
        double r8535 = b;
        double r8536 = c;
        double r8537 = r8535 * r8536;
        double r8538 = a;
        double r8539 = d;
        double r8540 = r8538 * r8539;
        double r8541 = r8537 - r8540;
        double r8542 = r8536 * r8536;
        double r8543 = r8539 * r8539;
        double r8544 = r8542 + r8543;
        double r8545 = r8541 / r8544;
        return r8545;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019191 
(FPCore (a b c d)
  :name "Complex division, imag part"

  :herbie-target
  (if (< (fabs d) (fabs c)) (/ (- b (* a (/ d c))) (+ c (* d (/ d c)))) (/ (+ (- a) (* b (/ c d))) (+ d (* c (/ c d)))))

  (/ (- (* b c) (* a d)) (+ (* c c) (* d d))))

Backtrace

get-representation: Unknown representation #f		L	C
loop	/data/pavpan/nightlies/herbie/interface2/src/points.rkt	122	4
prepare-points	/data/pavpan/nightlies/herbie/interface2/src/points.rkt	146	0
setup-prog!34	/data/pavpan/nightlies/herbie/interface2/src/mainloop.rkt	67	0
run-improve43	/data/pavpan/nightlies/herbie/interface2/src/mainloop.rkt	339	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