```
import math
# compute log(1+x) without loss of precision for small values of x
def log_one_plus_x(x):
if x <= -1.0:
raise FloatingPointError("argument must be > -1")
if abs(x) > 1e-4:
# x is large enough that the obvious evaluation is OK
return math.log(1.0 + x)
else:
# Use Taylor approx.
# log(1 + x) = x - x^2/2 with error roughly x^3/3
# Since |x| < 10^-4, |x|^3 < 10^-12,
# and the relative error is less than 10^-8
return (-0.5*x + 1.0)*x
```