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 r8183 = x;
        double r8184 = 4.0;
        double r8185 = r8183 + r8184;
        double r8186 = y;
        double r8187 = r8185 / r8186;
        double r8188 = r8183 / r8186;
        double r8189 = z;
        double r8190 = r8188 * r8189;
        double r8191 = r8187 - r8190;
        double r8192 = fabs(r8191);
        return r8192;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019194 +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	220	0
run-improve47	/data/pavpan/nightlies/herbie/various-cleanup/src/mainloop.rkt	342	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