\[x \cdot 0.5 + y \cdot \left(\left(1 - z\right) + \log z\right)\]

x \cdot 0.5 + y \cdot \left(\left(1 - z\right) + \log z\right)

double f(double x, double y, double z) {
        double r8559 = x;
        double r8560 = 0.5;
        double r8561 = r8559 * r8560;
        double r8562 = y;
        double r8563 = 1.0;
        double r8564 = z;
        double r8565 = r8563 - r8564;
        double r8566 = log(r8564);
        double r8567 = r8565 + r8566;
        double r8568 = r8562 * r8567;
        double r8569 = r8561 + r8568;
        return r8569;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019179 
(FPCore (x y z)
  :name "System.Random.MWC.Distributions:gamma from mwc-random-0.13.3.2"

  :herbie-target
  (- (+ y (* 0.5 x)) (* y (- z (log z))))

  (+ (* x 0.5) (* y (+ (- 1.0 z) (log z)))))

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