Specification

\[\begin{array}{l} \\ \frac{\pi}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right) \end{array} \]

(FPCore (x)
 :precision binary64
 (- (/ PI 2.0) (* 2.0 (asin (sqrt (/ (- 1.0 x) 2.0))))))

double code(double x) {
	return (((double) M_PI) / 2.0) - (2.0 * asin(sqrt(((1.0 - x) / 2.0))));
}

public static double code(double x) {
	return (Math.PI / 2.0) - (2.0 * Math.asin(Math.sqrt(((1.0 - x) / 2.0))));
}

def code(x):
	return (math.pi / 2.0) - (2.0 * math.asin(math.sqrt(((1.0 - x) / 2.0))))

function code(x)
	return Float64(Float64(pi / 2.0) - Float64(2.0 * asin(sqrt(Float64(Float64(1.0 - x) / 2.0)))))
end

function tmp = code(x)
	tmp = (pi / 2.0) - (2.0 * asin(sqrt(((1.0 - x) / 2.0))));
end

code[x_] := N[(N[(Pi / 2.0), $MachinePrecision] - N[(2.0 * N[ArcSin[N[Sqrt[N[(N[(1.0 - x), $MachinePrecision] / 2.0), $MachinePrecision]], $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision]

\begin{array}{l}

\\
\frac{\pi}{2} - 2 \cdot \sin^{-1} \left(\sqrt{\frac{1 - x}{2}}\right)
\end{array}

Reproduce

herbie shell --seed 2024021 
(FPCore (x)
  :name "Ian Simplification"
  :precision binary64

  :herbie-target
  (asin x)

  (- (/ PI 2.0) (* 2.0 (asin (sqrt (/ (- 1.0 x) 2.0))))))

Please file a bug report with this information.

Backtrace

inexact?: contract violation expected: number? given: (bf #e0.7853981633974482789994908671360462903976)		L	C
real->bigfloat	/usr/share/racket/pkgs/math-lib/math/private/bigfloat/mpfr.rkt	470	0
...row-higher-order.rkt:375:33	/usr/share/racket/collects/racket/contract/private/arrow-higher-order.rkt	375	33
f43	.../match/compiler.rkt	548	40
predicted-errors	/home/nightlies/herbie/error-explanations-2/src/error-table.rkt	52	0
mutate!	/home/nightlies/herbie/error-explanations-2/src/mainloop.rkt	354	0
run-improve!	/home/nightlies/herbie/error-explanations-2/src/mainloop.rkt	340	0
get-alternatives/report	/home/nightlies/herbie/error-explanations-2/src/sandbox.rkt	169	0
(unnamed)	/home/nightlies/herbie/error-explanations-2/src/sandbox.rkt	262	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