Open System Services Library Calls Reference Manual (G06.29+, H06.08+, J06.03+)

j0(3) OSS Library Calls Reference Manual
NAME
j0 - Computes the Bessel function of the first kind, of order 0 (zero)
LIBRARY
G-series native Guardian processes: $SYSTEM.SYSnn.ZCRESRL
G-series native OSS processes: /G/system/sysnn/zcresrl
H-series and J-series native Guardian processes: $SYSTEM.ZDLLnnn.ZCREDLL
32-bit H-series and J-series OSS processes: /G/system/zdllnnn/zcredll
64-bit H-series and J-series OSS processes: /G/system/zdllnnn/ycredll
SYNOPSIS
#include <math.h>
double j0(
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 j0( ) function computes the Bessel
function of x of the first kind, of order 0 (zero).
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 j0( ) function returns the Bessel function of x of the first kind, of order 0 (zero).
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 the value of 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 j0( ) 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), j1(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.
4−72 Hewlett-Packard Company 527187-017