Special math functions module

This module features additional coefficient-wise math functions available within the numext:: namespace for the scalar version, and as method and/or free functions of Array. Those include:

• erf
• erfc
• lgamma
• igamma
• igamma_der_a
• gamma_sample_der_alpha
• igammac
• digamma
• ndtri
• polygamma
• zeta
• betainc

Bessel Functions

• bessel_i0
• bessel_i0e
• bessel_i1
• bessel_i1e
• bessel_j0
• bessel_j1
• bessel_k0
• bessel_k0e
• bessel_k1
• bessel_k1e
• bessel_y0
• bessel_y1

The implementations are tuned for float and double, so they do not carry over to an arbitrary scalar. erf and erfc accept any other scalar type that declares its own erf / erfc in the namespace of that type, where argument-dependent lookup finds it; a scalar type that declares neither is rejected at compile time.

#include <contrib/Eigen/SpecialFunctions>