\[\log \left(\frac{1 - \varepsilon}{1 + \varepsilon}\right) \]
(FPCore (eps) :precision binary64 (log (/ (- 1.0 eps) (+ 1.0 eps))))
double code(double eps) {
	return log(((1.0 - eps) / (1.0 + eps)));
}
real(8) function code(eps)
    real(8), intent (in) :: eps
    code = log(((1.0d0 - eps) / (1.0d0 + eps)))
end function
public static double code(double eps) {
	return Math.log(((1.0 - eps) / (1.0 + eps)));
}
def code(eps):
	return math.log(((1.0 - eps) / (1.0 + eps)))
function code(eps)
	return log(Float64(Float64(1.0 - eps) / Float64(1.0 + eps)))
end
function tmp = code(eps)
	tmp = log(((1.0 - eps) / (1.0 + eps)));
end
code[eps_] := N[Log[N[(N[(1.0 - eps), $MachinePrecision] / N[(1.0 + eps), $MachinePrecision]), $MachinePrecision]], $MachinePrecision]
\log \left(\frac{1 - \varepsilon}{1 + \varepsilon}\right)

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2022203 
(FPCore (eps)
  :name "logq (problem 3.4.3)"
  :precision binary64

  :herbie-target
  (* -2.0 (+ (+ eps (/ (pow eps 3.0) 3.0)) (/ (pow eps 5.0) 5.0)))

  (log (/ (- 1.0 eps) (+ 1.0 eps))))

Backtrace

hash-ref: no value found for key key: '~LC
get-parametric-operator/data/pavpan/nightlies/herbie/enumo-rat/src/syntax/syntax.rkt2180
f336.../match/compiler.rkt54840
expand-parametric/data/pavpan/nightlies/herbie/enumo-rat/src/syntax/sugar.rkt620
(unnamed)/data/pavpan/nightlies/herbie/enumo-rat/src/syntax/rules.rkt1768
generate-rules-for/data/pavpan/nightlies/herbie/enumo-rat/src/syntax/rules.rkt1610
generate-missing-rules/data/pavpan/nightlies/herbie/enumo-rat/src/syntax/rules.rkt1870
(unnamed)/data/pavpan/nightlies/herbie/enumo-rat/src/syntax/rules.rkt2926
get-swaps/data/pavpan/nightlies/herbie/enumo-rat/src/symmetry.rkt60
connected-components/data/pavpan/nightlies/herbie/enumo-rat/src/symmetry.rkt170
run-improve!/data/pavpan/nightlies/herbie/enumo-rat/src/mainloop.rkt2960
(unnamed)/data/pavpan/nightlies/herbie/enumo-rat/src/sandbox.rkt556
(unnamed)/usr/share/racket/pkgs/profile-lib/main.rkt4010
profile-thunk/usr/share/racket/pkgs/profile-lib/main.rkt90
(unnamed)/usr/share/racket/collects/racket/engine.rkt4224