?

\[-1 < x \land x < 1\]

\[\frac{\log \left(1 - x\right)}{\log \left(1 + x\right)} \]

(FPCore (x) :precision binary64 (/ (log (- 1.0 x)) (log (+ 1.0 x))))

double code(double x) {
	return log((1.0 - x)) / log((1.0 + x));
}

real(8) function code(x)
    real(8), intent (in) :: x
    code = log((1.0d0 - x)) / log((1.0d0 + x))
end function

public static double code(double x) {
	return Math.log((1.0 - x)) / Math.log((1.0 + x));
}

def code(x):
	return math.log((1.0 - x)) / math.log((1.0 + x))

function code(x)
	return Float64(log(Float64(1.0 - x)) / log(Float64(1.0 + x)))
end

function tmp = code(x)
	tmp = log((1.0 - x)) / log((1.0 + x));
end

code[x_] := N[(N[Log[N[(1.0 - x), $MachinePrecision]], $MachinePrecision] / N[Log[N[(1.0 + x), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]

\frac{\log \left(1 - x\right)}{\log \left(1 + x\right)}

Reproduce?

Please include this information when filing a bug report:

herbie shell --seed 2023241 
(FPCore (x)
  :name "qlog (example 3.10)"
  :precision binary64
  :pre (and (< -1.0 x) (< x 1.0))

  :herbie-target
  (- (+ (+ (+ 1.0 x) (/ (* x x) 2.0)) (* 0.4166666666666667 (pow x 3.0))))

  (/ (log (- 1.0 x)) (log (+ 1.0 x))))

Backtrace

match: no matching clause for 'ival		L	C
compile-progs	/home/nightlies/herbie/arb-support/src/programs.rkt	122	0
make-search-func	/home/nightlies/herbie/arb-support/src/ground-truth.rkt	20	0
sample-points	/home/nightlies/herbie/arb-support/src/ground-truth.rkt	64	0
setup-context!	/home/nightlies/herbie/arb-support/src/mainloop.rkt	293	0
get-alternatives/report	/home/nightlies/herbie/arb-support/src/sandbox.rkt	148	0
(unnamed)	/home/nightlies/herbie/arb-support/src/sandbox.rkt	247	6
(unnamed)	/usr/share/racket/pkgs/profile-lib/main.rkt	40	10
profile-thunk	/usr/share/racket/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/usr/share/racket/collects/racket/engine.rkt	42	24