?

\[wj - \frac{wj \cdot e^{wj} - x}{e^{wj} + wj \cdot e^{wj}} \]
(FPCore (wj x)
 :precision binary64
 (- wj (/ (- (* wj (exp wj)) x) (+ (exp wj) (* wj (exp wj))))))
double code(double wj, double x) {
	return wj - (((wj * exp(wj)) - x) / (exp(wj) + (wj * exp(wj))));
}
real(8) function code(wj, x)
    real(8), intent (in) :: wj
    real(8), intent (in) :: x
    code = wj - (((wj * exp(wj)) - x) / (exp(wj) + (wj * exp(wj))))
end function
public static double code(double wj, double x) {
	return wj - (((wj * Math.exp(wj)) - x) / (Math.exp(wj) + (wj * Math.exp(wj))));
}
def code(wj, x):
	return wj - (((wj * math.exp(wj)) - x) / (math.exp(wj) + (wj * math.exp(wj))))
function code(wj, x)
	return Float64(wj - Float64(Float64(Float64(wj * exp(wj)) - x) / Float64(exp(wj) + Float64(wj * exp(wj)))))
end
function tmp = code(wj, x)
	tmp = wj - (((wj * exp(wj)) - x) / (exp(wj) + (wj * exp(wj))));
end
code[wj_, x_] := N[(wj - N[(N[(N[(wj * N[Exp[wj], $MachinePrecision]), $MachinePrecision] - x), $MachinePrecision] / N[(N[Exp[wj], $MachinePrecision] + N[(wj * N[Exp[wj], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
wj - \frac{wj \cdot e^{wj} - x}{e^{wj} + wj \cdot e^{wj}}

Reproduce?

Please include this information when filing a bug report:

herbie shell --seed 2023098 
(FPCore (wj x)
  :name "Jmat.Real.lambertw, newton loop step"
  :precision binary64

  :herbie-target
  (- wj (- (/ wj (+ wj 1.0)) (/ x (+ (exp wj) (* wj (exp wj))))))

  (- wj (/ (- (* wj (exp wj)) x) (+ (exp wj) (* wj (exp wj))))))

Backtrace

hash-ref: no value found for key key: 'falseLC
(unnamed)/home/nightlies/herbie/using-ruler-nightlies/src/syntax/syntax.rkt2302
f336.../match/compiler.rkt54840
expand-parametric/home/nightlies/herbie/using-ruler-nightlies/src/syntax/sugar.rkt620
(unnamed)/home/nightlies/herbie/using-ruler-nightlies/src/core/egg-herbie.rkt2559
rule->egg-rules/home/nightlies/herbie/using-ruler-nightlies/src/core/egg-herbie.rkt2240
expand-rules/home/nightlies/herbie/using-ruler-nightlies/src/core/egg-herbie.rkt4880
egraph-run-rules/home/nightlies/herbie/using-ruler-nightlies/src/core/egg-herbie.rkt5090
(unnamed)/home/nightlies/herbie/using-ruler-nightlies/src/core/simplify.rkt583
with-egraph/home/nightlies/herbie/using-ruler-nightlies/src/core/egg-herbie.rkt3330
simplify-batch/home/nightlies/herbie/using-ruler-nightlies/src/core/simplify.rkt230
(unnamed)/usr/share/racket/collects/racket/contract/private/arrow-higher-order.rkt37933
get-swaps/home/nightlies/herbie/using-ruler-nightlies/src/symmetry.rkt60
connected-components/home/nightlies/herbie/using-ruler-nightlies/src/symmetry.rkt180
run-improve!/home/nightlies/herbie/using-ruler-nightlies/src/mainloop.rkt3200
run-herbie/home/nightlies/herbie/using-ruler-nightlies/src/sandbox.rkt570
(unnamed)/home/nightlies/herbie/using-ruler-nightlies/src/sandbox.rkt1336
(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