Exception for Kahan p9 Example

Specification

\[\left(0 < x \land x < 1\right) \land y < 1\]

\[\begin{array}{l} \\ \frac{\left(x - y\right) \cdot \left(x + y\right)}{x \cdot x + y \cdot y} \end{array} \]

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

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

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

public static double code(double x, double y) {
	return ((x - y) * (x + y)) / ((x * x) + (y * y));
}

def code(x, y):
	return ((x - y) * (x + y)) / ((x * x) + (y * y))

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

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

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

\begin{array}{l}

\\
\frac{\left(x - y\right) \cdot \left(x + y\right)}{x \cdot x + y \cdot y}
\end{array}

Reproduce

herbie shell --seed 2024246 
(FPCore (x y)
  :name "Kahan p9 Example"
  :precision binary64
  :pre (and (and (< 0.0 x) (< x 1.0)) (< y 1.0))

  :alt
  (! :herbie-platform default (if (< 1/2 (fabs (/ x y)) 2) (/ (* (- x y) (+ x y)) (+ (* x x) (* y y))) (- 1 (/ 2 (+ 1 (* (/ x y) (/ x y)))))))

  (/ (* (- x y) (+ x y)) (+ (* x x) (* y y))))

Please file a bug report with this information.

Backtrace

map: contract violation expected: list? given: '(y . #hasheq((errs . (1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 ...		L	C
gen-map	/usr/local/racket/collects/racket/private/map.rkt	257	2
actual-errors	/home/nightlies/herbie/zane-concrete-values/src/core/explain.rkt	35	0
generate-timelines	/home/nightlies/herbie/zane-concrete-values/src/core/explain.rkt	493	0
explain!	/home/nightlies/herbie/zane-concrete-values/src/core/mainloop.rkt	322	0
run-improve!	/home/nightlies/herbie/zane-concrete-values/src/core/mainloop.rkt	44	0
get-alternatives/report	/home/nightlies/herbie/zane-concrete-values/src/api/sandbox.rkt	186	0
(unnamed)	/home/nightlies/herbie/zane-concrete-values/src/api/sandbox.rkt	282	6
(unnamed)	/usr/local/racket/share/pkgs/profile-lib/main.rkt	40	10
profile-thunk	/usr/local/racket/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/usr/local/racket/collects/racket/engine.rkt	42	24