28 Numerics library [numerics]

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

28.7.6 Mathematical special functions [sf.cmath] Associated Legendre functions [sf.cmath.assoc.legendre]

floating-point-type assoc_legendre(unsigned l, unsigned m, floating-point-type x); float assoc_legendref(unsigned l, unsigned m, float x); long double assoc_legendrel(unsigned l, unsigned m, long double x);
Effects: These functions compute the associated Legendre functions of their respective arguments l, m, and x.
where l is l, m is m, and x is x.
Remarks: The effect of calling each of these functions is implementation-defined if l >= 128.