This is an example of a library. You may see a list of other libraries used on Rosetta Code at Category:Solutions by Library.
The file builtins/mpfr.e as included in the standard distribution contains routines for performing arbitrary precision maths.
It is a wrapper for mpfr (ie arbitrary precision floats), which uses mpir (integers), which is itself a wrapper for gmp.
The following are all known uses of mpfr.e on rosettacode.
Pages in category "Mpfr"
The following 17 pages are in this category, out of 17 total.