Exception for Asymptote C

Math

\[\frac{x}{x + 1} - \frac{x + 1}{x - 1}\]

C

double f(double x) {
        double r8254 = x;
        double r8255 = 1.0;
        double r8256 = r8254 + r8255;
        double r8257 = r8254 / r8256;
        double r8258 = r8254 - r8255;
        double r8259 = r8256 / r8258;
        double r8260 = r8257 - r8259;
        return r8260;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019179 +o rules:numerics
(FPCore (x)
  :name "Asymptote C"
  (- (/ x (+ x 1.0)) (/ (+ x 1.0) (- x 1.0))))

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