Exception for Main:bigenough3 from C

Math

\[\sqrt{x + 1} - \sqrt{x}\]

C

double f(double x) {
        double r9776 = x;
        double r9777 = 1.0;
        double r9778 = r9776 + r9777;
        double r9779 = sqrt(r9778);
        double r9780 = sqrt(r9776);
        double r9781 = r9779 - r9780;
        return r9781;
}

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019173 +o rules:numerics
(FPCore (x)
  :name "Main:bigenough3 from C"

  :herbie-target
  (/ 1.0 (+ (sqrt (+ x 1.0)) (sqrt x)))

  (- (sqrt (+ x 1.0)) (sqrt x)))

Backtrace

atab-pick-alt: contract violation expected: alt? given: '(#<alt (λ (x) (- (sqrt (+ 1.0 x)) (sqrt x)))>) in: the range of the #:picking-func argument of (-> alt-table? #:only-fresh boolean? #:picking-func (-> (listof alt?) alt?) (values alt? alt-table?)) contract from: /data/pavpan/nightlies/herbie/no-costs-2/src/core/alt-table.rkt blaming: /data/pavpan/nightlies/herbie/no-costs-2/src/mainloop.rkt (assuming the contract is correct) at: /data/pavpan/nightlies/herbie/no-costs-2/src/core/alt-table.rkt:13.3		L	C
raise-blame-error16	/opt/racket-7.0/collects/racket/contract/private/blame.rkt	347	0
(unnamed)	/data/pavpan/nightlies/herbie/no-costs-2/src/core/alt-table.rkt	59	0
(unnamed)	/opt/racket-7.0/collects/racket/contract/private/arrow-val-first.rkt	388	18
choose-best-alt!	/data/pavpan/nightlies/herbie/no-costs-2/src/mainloop.rkt	110	0
run-iter!	/data/pavpan/nightlies/herbie/no-costs-2/src/mainloop.rkt	319	0
for-loop	/data/pavpan/nightlies/herbie/no-costs-2/src/mainloop.rkt	353	4
run-improve43	/data/pavpan/nightlies/herbie/no-costs-2/src/mainloop.rkt	338	0
(unnamed)	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	261	28
run	/opt/racket-7.0/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk16	/opt/racket-7.0/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.0/collects/racket/private/more-scheme.rkt	261	28