cc [ flags ] -I/usr/local/include file(s) -L/usr/local/lib -lmcw [ ... ] #include <mathcw.h> extern float bknf (int n, float x); extern double bkn (int n, double x); extern long double bknl (int n, long double x); extern __float80 bknw (int n, __float80 x); extern __float128 bknq (int n, __float128 x); extern long_long_double bknll (int n, long_long_double x); extern decimal_float bkndf (int n, decimal_float x); extern decimal_double bknd (int n, decimal_double x); extern decimal_long_double bkndl (int n, decimal_long_double x); extern decimal_long_long_double bkndll (int n, decimal_long_long_double x);
NB: Functions with prototypes containing underscores in type names may be available only with certain extended compilers.
The modified Bessel functions provided by these software implementations are defined according to Chapter 9, Bessel Functions of Integer Order, of the Handbook of Mathematical Functions, edited by Milton Abramowitz and Irene A. Stegun, National Bureau of Standards Applied Mathematics Series #55, US Department of Commerce, Washington, DC (1964).
The K(n,x) functions fall exponentially with increasing x, and underflow even with moderate x values. For that reason, there is a related family of functions that return values of this Bessel function increased by a factor of exp(x); see bksn(3CW).
If the argument is negative, errno is set to EDOM, and a quiet NaN is returned.
If the argument is zero, errno is set to ERANGE, and a positive Infinity (or the largest floating-point magnitude, if Infinity is not available) is returned.