libwignernj

libwignernj is a C99 library for the exact evaluation of Wignernj 3j, 6j and 9j symbols, Clebsch-Gordan coefficients, Racah W coefficients, Fano X coefficients, and Gaunt coefficients (over both complex and real spherical harmonics) using the prime-factorization scheme of Johansson and Forssen. All intermediate arithmetic is exact integer arithmetic; floating-point conversion happens only at the final step, so the returned values are correct to the last representable bit of the chosen output type: float, double, long double, IEEE 754 binary128 (via libquadmath), or, through the optional GNU MPFR back-end, arbitrary precision. Bindings are provided for C, C++11 (header-only), Fortran 90 (iso_c_binding) and Python 3.

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