Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2020355 
(FPCore (x y z t)
  :name "Numeric.SpecFunctions:incompleteGamma from math-functions-0.1.5.2, A"
  :precision binary64
  (+ (- (- (* x (log y)) y) z) (log t)))

Backtrace

/: division by zero		L	C
all-partitions	/data/pavpan/nightlies/herbie/taylor-one-var/src/core/taylor.rkt	337	0
(unnamed)	/data/pavpan/nightlies/herbie/taylor-one-var/src/core/taylor.rkt	355	23
hash-ref!	/opt/racket-7.9/collects/racket/private/more-scheme.rkt	377	2
next	/data/pavpan/nightlies/herbie/taylor-one-var/src/core/taylor.rkt	20	2
(unnamed)	/data/pavpan/nightlies/herbie/taylor-one-var/src/mainloop.rkt	153	4
loop	/data/pavpan/nightlies/herbie/taylor-one-var/src/mainloop.rkt	174	10
for-loop	/data/pavpan/nightlies/herbie/taylor-one-var/src/mainloop.rkt	169	8
for-loop	/data/pavpan/nightlies/herbie/taylor-one-var/src/mainloop.rkt	169	8
taylor-alt	/data/pavpan/nightlies/herbie/taylor-one-var/src/mainloop.rkt	161	0
gen-series!	/data/pavpan/nightlies/herbie/taylor-one-var/src/mainloop.rkt	185	0
run-iter!	/data/pavpan/nightlies/herbie/taylor-one-var/src/mainloop.rkt	380	0
run-improve	/data/pavpan/nightlies/herbie/taylor-one-var/src/mainloop.rkt	397	0
(unnamed)	/data/pavpan/nightlies/herbie/taylor-one-var/src/sandbox.rkt	54	6
run	/opt/racket-7.9/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk	/opt/racket-7.9/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.9/collects/racket/engine.rkt	42	24

Reproduce

herbie shell --seed 2020355 
(FPCore (x y z t)
  :name "Numeric.SpecFunctions:incompleteGamma from math-functions-0.1.5.2, A"
  :precision binary64
  (+ (- (- (* x (log y)) y) z) (log t)))