26 Numerics library [numerics]

26.8 Mathematical functions for floating-point types [c.math]

26.8.6 Mathematical special functions [sf.cmath] Spherical Bessel functions of the first kind [sf.cmath.sph.bessel]

double sph_bessel(unsigned n, double x); float sph_besself(unsigned n, float x); long double sph_bessell(unsigned n, long double x);
Effects: These functions compute the spherical Bessel functions of the first kind of their respective arguments n and x.
where n is n and x is x.
Remarks: The effect of calling each of these functions is implementation-defined if n >= 128.