\[\left(\left(\sqrt{\pi \cdot 2} \cdot {\left(\left(\left(z - 1\right) + 7\right) + 0.5\right)}^{\left(\left(z - 1\right) + 0.5\right)}\right) \cdot e^{-\left(\left(\left(z - 1\right) + 7\right) + 0.5\right)}\right) \cdot \left(\left(\left(\left(\left(\left(\left(\left(0.99999999999980993 + \frac{676.520368121885099}{\left(z - 1\right) + 1}\right) + \frac{-1259.13921672240281}{\left(z - 1\right) + 2}\right) + \frac{771.32342877765313}{\left(z - 1\right) + 3}\right) + \frac{-176.615029162140587}{\left(z - 1\right) + 4}\right) + \frac{12.5073432786869052}{\left(z - 1\right) + 5}\right) + \frac{-0.138571095265720118}{\left(z - 1\right) + 6}\right) + \frac{9.98436957801957158 \cdot 10^{-6}}{\left(z - 1\right) + 7}\right) + \frac{1.50563273514931162 \cdot 10^{-7}}{\left(z - 1\right) + 8}\right)\]
\left(\left(\sqrt{\pi \cdot 2} \cdot {\left(\left(\left(z - 1\right) + 7\right) + 0.5\right)}^{\left(\left(z - 1\right) + 0.5\right)}\right) \cdot e^{-\left(\left(\left(z - 1\right) + 7\right) + 0.5\right)}\right) \cdot \left(\left(\left(\left(\left(\left(\left(\left(0.99999999999980993 + \frac{676.520368121885099}{\left(z - 1\right) + 1}\right) + \frac{-1259.13921672240281}{\left(z - 1\right) + 2}\right) + \frac{771.32342877765313}{\left(z - 1\right) + 3}\right) + \frac{-176.615029162140587}{\left(z - 1\right) + 4}\right) + \frac{12.5073432786869052}{\left(z - 1\right) + 5}\right) + \frac{-0.138571095265720118}{\left(z - 1\right) + 6}\right) + \frac{9.98436957801957158 \cdot 10^{-6}}{\left(z - 1\right) + 7}\right) + \frac{1.50563273514931162 \cdot 10^{-7}}{\left(z - 1\right) + 8}\right)
double f(double z) {
        double r8524 = atan2(1.0, 0.0);
        double r8525 = 2.0;
        double r8526 = r8524 * r8525;
        double r8527 = sqrt(r8526);
        double r8528 = z;
        double r8529 = 1.0;
        double r8530 = r8528 - r8529;
        double r8531 = 7.0;
        double r8532 = r8530 + r8531;
        double r8533 = 0.5;
        double r8534 = r8532 + r8533;
        double r8535 = r8530 + r8533;
        double r8536 = pow(r8534, r8535);
        double r8537 = r8527 * r8536;
        double r8538 = -r8534;
        double r8539 = exp(r8538);
        double r8540 = r8537 * r8539;
        double r8541 = 0.9999999999998099;
        double r8542 = 676.5203681218851;
        double r8543 = r8530 + r8529;
        double r8544 = r8542 / r8543;
        double r8545 = r8541 + r8544;
        double r8546 = -1259.1392167224028;
        double r8547 = r8530 + r8525;
        double r8548 = r8546 / r8547;
        double r8549 = r8545 + r8548;
        double r8550 = 771.3234287776531;
        double r8551 = 3.0;
        double r8552 = r8530 + r8551;
        double r8553 = r8550 / r8552;
        double r8554 = r8549 + r8553;
        double r8555 = -176.6150291621406;
        double r8556 = 4.0;
        double r8557 = r8530 + r8556;
        double r8558 = r8555 / r8557;
        double r8559 = r8554 + r8558;
        double r8560 = 12.507343278686905;
        double r8561 = 5.0;
        double r8562 = r8530 + r8561;
        double r8563 = r8560 / r8562;
        double r8564 = r8559 + r8563;
        double r8565 = -0.13857109526572012;
        double r8566 = 6.0;
        double r8567 = r8530 + r8566;
        double r8568 = r8565 / r8567;
        double r8569 = r8564 + r8568;
        double r8570 = 9.984369578019572e-06;
        double r8571 = r8570 / r8532;
        double r8572 = r8569 + r8571;
        double r8573 = 1.5056327351493116e-07;
        double r8574 = 8.0;
        double r8575 = r8530 + r8574;
        double r8576 = r8573 / r8575;
        double r8577 = r8572 + r8576;
        double r8578 = r8540 * r8577;
        return r8578;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019194 
(FPCore (z)
  :name "Jmat.Real.gamma, branch z greater than 0.5"
  (* (* (* (sqrt (* PI 2.0)) (pow (+ (+ (- z 1.0) 7.0) 0.5) (+ (- z 1.0) 0.5))) (exp (- (+ (+ (- z 1.0) 7.0) 0.5)))) (+ (+ (+ (+ (+ (+ (+ (+ 0.9999999999998099 (/ 676.5203681218851 (+ (- z 1.0) 1.0))) (/ -1259.1392167224028 (+ (- z 1.0) 2.0))) (/ 771.3234287776531 (+ (- z 1.0) 3.0))) (/ -176.6150291621406 (+ (- z 1.0) 4.0))) (/ 12.507343278686905 (+ (- z 1.0) 5.0))) (/ -0.13857109526572012 (+ (- z 1.0) 6.0))) (/ 9.984369578019572e-06 (+ (- z 1.0) 7.0))) (/ 1.5056327351493116e-07 (+ (- z 1.0) 8.0)))))

Backtrace

result arity mismatch; expected number of values not received expected: 2 received: 1 in: local-binding form values...: 0LC
loop/data/pavpan/nightlies/herbie/various-cleanup/src/core/extraction.rkt252
(unnamed)/data/pavpan/nightlies/herbie/various-cleanup/src/core/simplify.rkt260
simplify!/data/pavpan/nightlies/herbie/various-cleanup/src/mainloop.rkt2200
run-improve47/data/pavpan/nightlies/herbie/various-cleanup/src/mainloop.rkt3420
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128
run/opt/racket-7.0/share/pkgs/profile-lib/main.rkt392
profile-thunk16/opt/racket-7.0/share/pkgs/profile-lib/main.rkt90
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128