Exception for Hyperbolic sine

Math

\[\frac{e^{x} - e^{-x}}{2}\]

C

double f(double x) {
        double r8110 = x;
        double r8111 = exp(r8110);
        double r8112 = -r8110;
        double r8113 = exp(r8112);
        double r8114 = r8111 - r8113;
        double r8115 = 2.0;
        double r8116 = r8114 / r8115;
        return r8116;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019194 +o rules:numerics
(FPCore (x)
  :name "Hyperbolic sine"
  (/ (- (exp x) (exp (- x))) 2.0))

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	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