How do you print the EXACT value of a floating point number?

Question

First of all, this is not a floating point newbie question. I know results of floating point arithmetic (not to mention transcendental functions) usually cannot be represent

Answer 1

Well being no floating point expert myself, I'd defer to using a well tested open source library.

The GNU MPFR is a good one.

The MPFR library is a C library for multiple-precision floating-point computations with correct rounding. The main goal of MPFR is to provide a library for multiple-precision floating-point computation which is both efficient and has a well-defined semantics.