i8lib, a C code which contains a number of utility routines for "I8" or "double precision integer" arithmetic.
The information on this web page is distributed under the MIT license.
i8lib is available in a C version and a C++ version and a Fortran90 version and a Python version.
c8lib, a C code which implements certain elementary functions for "C8" or double precision complex variables;
i4lib, a C code which contains many utility routines, using "I4" or "single precision integer" arithmetic.
r8lib, a C code which contains many utility routines, using "R8" or "double precision real" arithmetic.