Guardian Native C Library Calls Reference Manual (G06.28+, H06.04+)

j1(3) Guardian Native C Library Calls Reference Manual
NAME
j1 - Computes the Bessel function of the first kind, of order 1
LIBRARY
G-series native Guardian processes: $SYSTEM.SYSnn.ZCRESRL
G-series native OSS processes: /G/system/sysnn/zcresrl
H-series native Guardian processes: $SYSTEM.ZDLLnnn.ZCREDLL
H-series OSS processes: /G/system/zdllnnn/zcredll
SYNOPSIS
#include <math.h>
double j1(
double x);
PARAMETERS
x Specifies the double value for which the function is to be computed.
DESCRIPTION
The j0( ), j1(), jn(), y0(), y1(), and yn() functions are Bessel functions that are used to compute
wave variables, primarily in the field of communications. The j1( ) function computes the Bessel
function of x of the first kind, of order 1.
NOTES
This function supports both IEEE Std 754-1985 floating-point and Tandem floating-point values
in the native environment. IEEE values can include NaN and infinity, and the sign of 0.0 (zero)
can be either positive or negative. Refer to the fp_class(3) reference page for a description of
IEEE value classes.
Guardian functions are available to convert between floating-point formats. Refer to the Guar-
dian Programmer’s Guide for a discussion of floating-point conversions.
RETURN VALUES
The j1( ) function returns the Bessel function of x of the first kind, of order 1. If the correct result
would cause underflow, 0.0 (zero) is returned. If the correct result would cause overflow, 0.0
(zero) is returned and errno is set to [ERANGE].
If the x parameter is too large in magnitude, the value 0.0 (zero) is returned and errno is set to
[ERANGE].
For IEEE floating-point values, if x is NaN, NaN is returned. If the value of x is positive infinity,
positive infinity is returned and errno is set to [ERANGE].
ERRORS
If any of the following conditions occurs, the j1() function sets errno to the corresponding value:
[ERANGE] The value of x was too large in magnitude, positive infinity, or the result would
cause overflow.
RELATED INFORMATION
Functions: fp_class(3), isnan(3), j0(3), jn(3), y0(3), y1(3), yn(3).
STANDARDS CONFORMANCE
THe XPG4 Version 2 specification leaves some features to the implementing vendor to define.
The following features are affected in the HP implementation:
• For IEEE floating-point data, errno is not set to [EDOM] when the value of x is NaN.
4−4 Hewlett-Packard Company 527192-005