Intel® Fortran Compiler 18.0 Developer Guide and Reference
Portability Functions: Compute the single-precision values of Bessel functions of the first and second kinds.
USE IFPORT
result = BESJ0 (value)
result = BESJ1 (value)
result = BESJN (n, value)
result = BESY0 (posvalue)
result = BESY1 (posvalue)
result = BESYN (n, value)
value |
(Input) REAL(4). Independent variable for a Bessel function. |
n |
(Input) INTEGER(4). Specifies the order of the selected Bessel function computation. |
posvalue |
(Input) REAL(4). Independent variable for a Bessel function. Must be greater than or equal to zero. |
BESJ0, BESJ1, and BESJN return Bessel functions of the first kind, orders 0, 1, and n, respectively, with the independent variable posvalue.
BESY0, BESY1, and BESYN return Bessel functions of the second kind, orders 0, 1, and n, respectively, with the independent variable posvalue.
Negative arguments cause BESY0, BESY1, and BESYN to return QNAN.
Bessel functions are explained more fully in most mathematics reference books, such as the Handbook of Mathematical Functions (Abramowitz and Stegun. Washington: U.S. Government Printing Office, 1964). These functions are commonly used in the mathematics of electromagnetic wave theory.
See the descriptions of the BESSEL_* functions, if you need to use quad-precision (REAL(16)).