?

\[x - \frac{y}{1 + \frac{x \cdot y}{2}} \]
(FPCore (x y) :precision binary64 (- x (/ y (+ 1.0 (/ (* x y) 2.0)))))
double code(double x, double y) {
	return x - (y / (1.0 + ((x * y) / 2.0)));
}
real(8) function code(x, y)
    real(8), intent (in) :: x
    real(8), intent (in) :: y
    code = x - (y / (1.0d0 + ((x * y) / 2.0d0)))
end function
public static double code(double x, double y) {
	return x - (y / (1.0 + ((x * y) / 2.0)));
}
def code(x, y):
	return x - (y / (1.0 + ((x * y) / 2.0)))
function code(x, y)
	return Float64(x - Float64(y / Float64(1.0 + Float64(Float64(x * y) / 2.0))))
end
function tmp = code(x, y)
	tmp = x - (y / (1.0 + ((x * y) / 2.0)));
end
code[x_, y_] := N[(x - N[(y / N[(1.0 + N[(N[(x * y), $MachinePrecision] / 2.0), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]), $MachinePrecision]
x - \frac{y}{1 + \frac{x \cdot y}{2}}

Reproduce?

Please include this information when filing a bug report:

herbie shell --seed 2023033 
(FPCore (x y)
  :name "Data.Number.Erf:$cinvnormcdf from erf-2.0.0.0, B"
  :precision binary64
  (- x (/ y (+ 1.0 (/ (* x y) 2.0)))))

Backtrace

map: contract violation expected: list? given: #<eof>LC
gen-map/usr/share/racket/collects/racket/private/map.rkt2572
run-egglog/home/nightlies/herbie/oflatt-egglog-ctx/src/egglog/run-egglog.rkt14560
run-simplify-input/home/nightlies/herbie/oflatt-egglog-ctx/src/core/simplify.rkt730
simplify-batch/home/nightlies/herbie/oflatt-egglog-ctx/src/core/simplify.rkt480
(unnamed)/usr/share/racket/collects/racket/contract/private/arrow-higher-order.rkt37933
simplify!/home/nightlies/herbie/oflatt-egglog-ctx/src/patch.rkt2460
patch-table-run/home/nightlies/herbie/oflatt-egglog-ctx/src/patch.rkt3180
(unnamed)/usr/share/racket/collects/racket/contract/private/arrow-val-first.rkt48618
run-iter!/home/nightlies/herbie/oflatt-egglog-ctx/src/mainloop.rkt2620
mutate!/home/nightlies/herbie/oflatt-egglog-ctx/src/mainloop.rkt3720
run-improve!/home/nightlies/herbie/oflatt-egglog-ctx/src/mainloop.rkt3200
run-herbie/home/nightlies/herbie/oflatt-egglog-ctx/src/sandbox.rkt570
(unnamed)/home/nightlies/herbie/oflatt-egglog-ctx/src/sandbox.rkt1336
(unnamed)/usr/share/racket/pkgs/profile-lib/main.rkt4010
profile-thunk/usr/share/racket/pkgs/profile-lib/main.rkt90
(unnamed)/usr/share/racket/collects/racket/engine.rkt4224