Exception for ENA, Section 1.4, Exercise 4d

Specification

\[\left(0 \leq x \land x \leq 1000000000\right) \land \left(-1 \leq \varepsilon \land \varepsilon \leq 1\right)\]

Math

\[\begin{array}{l} \\ x - \sqrt{x \cdot x - \varepsilon} \end{array} \]

FPCore

(FPCore (x eps) :precision binary64 (- x (sqrt (- (* x x) eps))))

C

double code(double x, double eps) {
	return x - sqrt(((x * x) - eps));
}

Fortran

real(8) function code(x, eps)
    real(8), intent (in) :: x
    real(8), intent (in) :: eps
    code = x - sqrt(((x * x) - eps))
end function

Java

public static double code(double x, double eps) {
	return x - Math.sqrt(((x * x) - eps));
}

Python

def code(x, eps):
	return x - math.sqrt(((x * x) - eps))

Julia

function code(x, eps)
	return Float64(x - sqrt(Float64(Float64(x * x) - eps)))
end

MATLAB

function tmp = code(x, eps)
	tmp = x - sqrt(((x * x) - eps));
end

Wolfram

code[x_, eps_] := N[(x - N[Sqrt[N[(N[(x * x), $MachinePrecision] - eps), $MachinePrecision]], $MachinePrecision]), $MachinePrecision]

Reproduce

herbie shell --seed 2024246 
(FPCore (x eps)
  :name "ENA, Section 1.4, Exercise 4d"
  :precision binary64
  :pre (and (and (<= 0.0 x) (<= x 1000000000.0)) (and (<= -1.0 eps) (<= eps 1.0)))

  :alt
  (! :herbie-platform default (/ eps (+ x (sqrt (- (* x x) eps)))))

  (- x (sqrt (- (* x x) eps))))

Please file a bug report with this information.

Backtrace

map: contract violation expected: list? given: '((-.f64 x (sqrt.f64 (-.f64 (*.f64 x x) eps))) . #hasheq((errs . (1 1 4071933343233423473 1 1 610349348897529034 1 2352791112050720444 1 1643568378178688590 1207575131313819795 1779696942774164221 1 1 1 1 1 3460389419954598121 3076142920722939119 144165...		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