\[x + \frac{y}{1.12837916709551256 \cdot e^{z} - x \cdot y}\]
x + \frac{y}{1.12837916709551256 \cdot e^{z} - x \cdot y}
double f(double x, double y, double z) {
        double r8510 = x;
        double r8511 = y;
        double r8512 = 1.1283791670955126;
        double r8513 = z;
        double r8514 = exp(r8513);
        double r8515 = r8512 * r8514;
        double r8516 = r8510 * r8511;
        double r8517 = r8515 - r8516;
        double r8518 = r8511 / r8517;
        double r8519 = r8510 + r8518;
        return r8519;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019194 
(FPCore (x y z)
  :name "Numeric.SpecFunctions:invErfc from math-functions-0.1.5.2, A"

  :herbie-target
  (+ x (/ 1.0 (- (* (/ 1.1283791670955126 y) (exp z)) x)))

  (+ x (/ y (- (* 1.1283791670955126 (exp z)) (* x y)))))

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