\[2 \cdot \left(x \cdot x - x \cdot y\right)\]
2 \cdot \left(x \cdot x - x \cdot y\right)
double f(double x, double y) {
        double r8898 = 2.0;
        double r8899 = x;
        double r8900 = r8899 * r8899;
        double r8901 = y;
        double r8902 = r8899 * r8901;
        double r8903 = r8900 - r8902;
        double r8904 = r8898 * r8903;
        return r8904;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019194 
(FPCore (x y)
  :name "Linear.Matrix:fromQuaternion from linear-1.19.1.3, A"

  :herbie-target
  (* (* x 2.0) (- x y))

  (* 2.0 (- (* x x) (* 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