Specification

\[\begin{array}{l} \\ \frac{2}{1 + e^{-2 \cdot x}} - 1 \end{array} \]

(FPCore (x y) :precision binary64 (- (/ 2.0 (+ 1.0 (exp (* -2.0 x)))) 1.0))

double code(double x, double y) {
	return (2.0 / (1.0 + exp((-2.0 * x)))) - 1.0;
}

real(8) function code(x, y)
    real(8), intent (in) :: x
    real(8), intent (in) :: y
    code = (2.0d0 / (1.0d0 + exp(((-2.0d0) * x)))) - 1.0d0
end function

public static double code(double x, double y) {
	return (2.0 / (1.0 + Math.exp((-2.0 * x)))) - 1.0;
}

def code(x, y):
	return (2.0 / (1.0 + math.exp((-2.0 * x)))) - 1.0

function code(x, y)
	return Float64(Float64(2.0 / Float64(1.0 + exp(Float64(-2.0 * x)))) - 1.0)
end

function tmp = code(x, y)
	tmp = (2.0 / (1.0 + exp((-2.0 * x)))) - 1.0;
end

code[x_, y_] := N[(N[(2.0 / N[(1.0 + N[Exp[N[(-2.0 * x), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]), $MachinePrecision] - 1.0), $MachinePrecision]

\begin{array}{l}

\\
\frac{2}{1 + e^{-2 \cdot x}} - 1
\end{array}

Reproduce

herbie shell --seed 2024012 
(FPCore (x y)
  :name "Logistic function from Lakshay Garg"
  :precision binary64
  (- (/ 2.0 (+ 1.0 (exp (* -2.0 x)))) 1.0))

Please file a bug report with this information.

Backtrace

car: contract violation expected: pair? given: '#(#s(si 18 77) (#s(si 19 71)))		L	C
err-lsts->split-indices	/home/nightlies/herbie/zane-regimes-2/src/core/regimes.rkt	176	0
option-on-expr	/home/nightlies/herbie/zane-regimes-2/src/core/regimes.rkt	106	0
infer-splitpoints	/home/nightlies/herbie/zane-regimes-2/src/core/regimes.rkt	39	0
loop	/home/nightlies/herbie/zane-regimes-2/src/core/regimes.rkt	27	2
extract!	/home/nightlies/herbie/zane-regimes-2/src/mainloop.rkt	352	0
run-improve!	/home/nightlies/herbie/zane-regimes-2/src/mainloop.rkt	326	0
get-alternatives/report	/home/nightlies/herbie/zane-regimes-2/src/sandbox.rkt	150	0
(unnamed)	/home/nightlies/herbie/zane-regimes-2/src/sandbox.rkt	246	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