Error in 0.0ms

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2019067 
(FPCore (c_p c_n t s)
  :name "Harley's example"
  :pre (and (< 0 c_p) (< 0 c_n))

  :herbie-target
  (* (pow (/ (+ 1 (exp (- t))) (+ 1 (exp (- s)))) c_p) (pow (/ (+ 1 (exp t)) (+ 1 (exp s))) c_n))

  (/ (* (pow (/ 1 (+ 1 (exp (- s)))) c_p) (pow (- 1 (/ 1 (+ 1 (exp (- s))))) c_n)) (* (pow (/ 1 (+ 1 (exp (- t)))) c_p) (pow (- 1 (/ 1 (+ 1 (exp (- t))))) c_n))))

Backtrace

build-list: contract violation expected: exact-nonnegative-integer? given: '(0)LC
build-list/opt/racket-7.0/collects/racket/private/list.rkt2962
debug-print/data/pavpan/nightlies/herbie/develop/src/debug.rkt1070
run-improve43/data/pavpan/nightlies/herbie/develop/src/mainloop.rkt3460
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128
run/opt/racket-7.0/share/pkgs/profile-lib/main.rkt392
profile-thunk16/opt/racket-7.0/share/pkgs/profile-lib/main.rkt90
(unnamed)/opt/racket-7.0/collects/racket/private/more-scheme.rkt26128