wip/mppp NetBSD

mp++ is a C++11 library for multiprecision arithmetic, currently supporting arbitrary-precision integers, rationals and floats, and quadruple-precision floats.

Based on well-known libraries such as GMP, MPFR, and others, mp++ was initially conceived as a GMP wrapper with a special focus on performance with small operands. In particular, a small buffer optimisation and custom implementations of basic mathematical primitives are instrumental in achieving a performance increase, with respect to GMP and other integer multiprecision libraries, which can be substantial (see the benchmarks section of the documentation). The price to pay is a small overhead when operating on large integers.

Eventually, a multiprecision rational class and two multiprecision floating-point classes were added, and today a secondary objective of mp++ is to provide a modern, consistent and unified C++ interface to several lower-level multiprecision libraries