Also the AOSP calculator, of course[1,2,3].
[1] https://chadnauseam.com/coding/random/calculator-app
[2] https://dl.acm.org/doi/10.1145/2911981
[3] https://dl.acm.org/doi/10.1145/3385412.3386037
Ivy does big numbers (not arbitrary) but does rationals too. It's an APL subset.
0.1 + 0.2 3/10