\[\frac{2 + \left(\left(\sqrt{2} \cdot \left(\sin x - \frac{\sin y}{16}\right)\right) \cdot \left(\sin y - \frac{\sin x}{16}\right)\right) \cdot \left(\cos x - \cos y\right)}{3 \cdot \left(\left(1 + \frac{\sqrt{5} - 1}{2} \cdot \cos x\right) + \frac{3 - \sqrt{5}}{2} \cdot \cos y\right)}\]

\frac{2 + \left(\left(\sqrt{2} \cdot \left(\sin x - \frac{\sin y}{16}\right)\right) \cdot \left(\sin y - \frac{\sin x}{16}\right)\right) \cdot \left(\cos x - \cos y\right)}{3 \cdot \left(\left(1 + \frac{\sqrt{5} - 1}{2} \cdot \cos x\right) + \frac{3 - \sqrt{5}}{2} \cdot \cos y\right)}

double f(double x, double y) {
        double r8438 = 2.0;
        double r8439 = sqrt(r8438);
        double r8440 = x;
        double r8441 = sin(r8440);
        double r8442 = y;
        double r8443 = sin(r8442);
        double r8444 = 16.0;
        double r8445 = r8443 / r8444;
        double r8446 = r8441 - r8445;
        double r8447 = r8439 * r8446;
        double r8448 = r8441 / r8444;
        double r8449 = r8443 - r8448;
        double r8450 = r8447 * r8449;
        double r8451 = cos(r8440);
        double r8452 = cos(r8442);
        double r8453 = r8451 - r8452;
        double r8454 = r8450 * r8453;
        double r8455 = r8438 + r8454;
        double r8456 = 3.0;
        double r8457 = 1.0;
        double r8458 = 5.0;
        double r8459 = sqrt(r8458);
        double r8460 = r8459 - r8457;
        double r8461 = r8460 / r8438;
        double r8462 = r8461 * r8451;
        double r8463 = r8457 + r8462;
        double r8464 = r8456 - r8459;
        double r8465 = r8464 / r8438;
        double r8466 = r8465 * r8452;
        double r8467 = r8463 + r8466;
        double r8468 = r8456 * r8467;
        double r8469 = r8455 / r8468;
        return r8469;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019179 
(FPCore (x y)
  :name "Diagrams.TwoD.Path.Metafont.Internal:hobbyF from diagrams-contrib-1.3.0.5"
  (/ (+ 2.0 (* (* (* (sqrt 2.0) (- (sin x) (/ (sin y) 16.0))) (- (sin y) (/ (sin x) 16.0))) (- (cos x) (cos y)))) (* 3.0 (+ (+ 1.0 (* (/ (- (sqrt 5.0) 1.0) 2.0) (cos x))) (* (/ (- 3.0 (sqrt 5.0)) 2.0) (cos y))))))

Backtrace

result arity mismatch; expected number of values not received expected: 2 received: 1 in: local-binding form values...: 0		L	C
loop	/data/pavpan/nightlies/herbie/various-cleanup/src/core/extraction.rkt	25	2
(unnamed)	/data/pavpan/nightlies/herbie/various-cleanup/src/core/simplify.rkt	26	0
simplify!	/data/pavpan/nightlies/herbie/various-cleanup/src/mainloop.rkt	217	0
run-improve43	/data/pavpan/nightlies/herbie/various-cleanup/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