\[x + \frac{y}{1.12837916709551256 \cdot e^{z} - x \cdot y}\]
x + \frac{y}{1.12837916709551256 \cdot e^{z} - x \cdot y}
double f(double x, double y, double z) {
        double r8854 = x;
        double r8855 = y;
        double r8856 = 1.1283791670955126;
        double r8857 = z;
        double r8858 = exp(r8857);
        double r8859 = r8856 * r8858;
        double r8860 = r8854 * r8855;
        double r8861 = r8859 - r8860;
        double r8862 = r8855 / r8861;
        double r8863 = r8854 + r8862;
        return r8863;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019179 
(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.rkt2170
run-improve43/data/pavpan/nightlies/herbie/various-cleanup/src/mainloop.rkt3390
(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