Finding the number of digits on the iPhone Calculator

[Albert Chan]

Try to find eps, such that eps + 1 - 1 = 0

For example, my ipad Sci:Pro Calc apps has 128 bits precision

Code:

2 ^ -127 + 1 - 1 =
5.877471754111438e-39

2 ^ -128 + 1 - 1 =
0

Update: it is safer to double check around found eps, since 1+eps is a half-way case.
3e-39 + 1 - 1 → 5.877471754111438e-39
2e-39 + 1 - 1 → 0