Exception for fabs fraction 1

Math

\[\left|\frac{x + 4}{y} - \frac{x}{y} \cdot z\right|\]

C

double f(double x, double y, double z) {
        double r8230 = x;
        double r8231 = 4.0;
        double r8232 = r8230 + r8231;
        double r8233 = y;
        double r8234 = r8232 / r8233;
        double r8235 = r8230 / r8233;
        double r8236 = z;
        double r8237 = r8235 * r8236;
        double r8238 = r8234 - r8237;
        double r8239 = fabs(r8238);
        return r8239;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019179 +o rules:numerics
(FPCore (x y z)
  :name "fabs fraction 1"
  (fabs (- (/ (+ x 4.0) y) (* (/ x y) 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