?

\[\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d} \]
(FPCore (a b c d)
 :precision binary64
 (/ (- (* b c) (* a d)) (+ (* c c) (* d d))))
double code(double a, double b, double c, double d) {
	return ((b * c) - (a * d)) / ((c * c) + (d * d));
}
real(8) function code(a, b, c, d)
    real(8), intent (in) :: a
    real(8), intent (in) :: b
    real(8), intent (in) :: c
    real(8), intent (in) :: d
    code = ((b * c) - (a * d)) / ((c * c) + (d * d))
end function
public static double code(double a, double b, double c, double d) {
	return ((b * c) - (a * d)) / ((c * c) + (d * d));
}
def code(a, b, c, d):
	return ((b * c) - (a * d)) / ((c * c) + (d * d))
function code(a, b, c, d)
	return Float64(Float64(Float64(b * c) - Float64(a * d)) / Float64(Float64(c * c) + Float64(d * d)))
end
function tmp = code(a, b, c, d)
	tmp = ((b * c) - (a * d)) / ((c * c) + (d * d));
end
code[a_, b_, c_, d_] := N[(N[(N[(b * c), $MachinePrecision] - N[(a * d), $MachinePrecision]), $MachinePrecision] / N[(N[(c * c), $MachinePrecision] + N[(d * d), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
\frac{b \cdot c - a \cdot d}{c \cdot c + d \cdot d}

Reproduce?

Please include this information when filing a bug report:

herbie shell --seed 2023098 
(FPCore (a b c d)
  :name "Complex division, imag part"
  :precision binary64

  :herbie-target
  (if (< (fabs d) (fabs c)) (/ (- b (* a (/ d c))) (+ c (* d (/ d c)))) (/ (+ (- a) (* b (/ c d))) (+ d (* c (/ c d)))))

  (/ (- (* b c) (* a d)) (+ (* c c) (* d d))))

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