\[\frac{\left(1 - x\right) \cdot \left(3 - x\right)}{y \cdot 3}\]
\frac{\left(1 - x\right) \cdot \left(3 - x\right)}{y \cdot 3}
double f(double x, double y) {
        double r8957 = 1.0;
        double r8958 = x;
        double r8959 = r8957 - r8958;
        double r8960 = 3.0;
        double r8961 = r8960 - r8958;
        double r8962 = r8959 * r8961;
        double r8963 = y;
        double r8964 = r8963 * r8960;
        double r8965 = r8962 / r8964;
        return r8965;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019179 
(FPCore (x y)
  :name "Diagrams.TwoD.Arc:bezierFromSweepQ1 from diagrams-lib-1.3.0.3"

  :herbie-target
  (* (/ (- 1.0 x) y) (/ (- 3.0 x) 3.0))

  (/ (* (- 1.0 x) (- 3.0 x)) (* y 3.0)))

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.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