[junon]

Not very reliable. For precision one usually seeks out the MPFR library or something similar.

[zoomablemind]

If anyone else wonders, MPFR (Multi-Precision Floating-point calc with correct Rounding). The application domain is Interval Math [1].

[1]:http://cs.utep.edu/interval-comp/applications.html

[adgjlsfhk1]

ARB https://arblib.org/ is often better than mpfr.

[junon]

Thanks, that's a new one.