Exception for Commute and associate

Math

\[\left(\left(x + y\right) + z\right) - \left(x + \left(y + z\right)\right)\]

C

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

Reproduce

Please include this information when filing a bug report:

herbie shell --seed 2020165 
(FPCore (x y z)
  :name "Commute and associate"
  :precision binary64
  (- (+ (+ x y) z) (+ x (+ y z))))

Backtrace

ival-hi: contract violation expected: ival? given: #<procedure:interval>		L	C
for-loop	/data/pavpan/nightlies/herbie/ival-find-range/src/sampling.rkt	37	11
hyperrect-weight	/data/pavpan/nightlies/herbie/ival-find-range/src/sampling.rkt	36	0
total-weight	/data/pavpan/nightlies/herbie/ival-find-range/src/sampling.rkt	113	2
log-space-improvement	/data/pavpan/nightlies/herbie/ival-find-range/src/sampling.rkt	110	0
(unnamed)	/opt/racket-7.5/collects/racket/contract/private/arrow-higher-order.rkt	375	33
get-hyperrects	/data/pavpan/nightlies/herbie/ival-find-range/src/sampling.rkt	123	0
make-sampler	/data/pavpan/nightlies/herbie/ival-find-range/src/sampling.rkt	147	0
prepare-points-intervals	/data/pavpan/nightlies/herbie/ival-find-range/src/points.rkt	90	0
run-improve47	/data/pavpan/nightlies/herbie/ival-find-range/src/mainloop.rkt	365	0
.../more-scheme.rkt:261:28	unknown
run	/opt/racket-7.5/share/pkgs/profile-lib/main.rkt	39	2
profile-thunk16	/opt/racket-7.5/share/pkgs/profile-lib/main.rkt	9	0
(unnamed)	/opt/racket-7.5/collects/racket/private/more-scheme.rkt	261	28

Reproduce

herbie shell --seed 2020165 
(FPCore (x y z)
  :name "Commute and associate"
  :precision binary64
  (- (+ (+ x y) z) (+ x (+ y z))))