Guardian Native C Library Calls Reference Manual (G06.28+, H06.05+)

ilogb(3) Guardian Native C Library Calls Reference Manual
NAME
ilogb - Computes the radix-independent exponent as an integer
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/sysnn/zcredll
SYNOPSIS
#include <math.h>
int ilogb(
double x);
PARAMETERS
x Specifies the value for which the exponent is to be calculated.
DESCRIPTION
The ilogb() function returns the exponent part of the floating-point value given as the x parame-
ter. More precisely, it calculates the base-r logarithm (where r is the radix of the machine’s
floating-point arithmetic) of the absolute value of x and returns the result as a signed integer.
NOTES
The ilogb() function can be called only by native processes.
This function supports both IEEE Std 754-1985 floating-point and Tandem floating-point values.
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 ilogb() function returns the exponent of x as an integer.
For IEEE floating-point values, when x has a value of 0.0 (zero) or NaN, ilogb() returns the value
INT_MIN. When x has a value of positive or negative infinity, ilog() returns the value
INT_MAX.
For Tandem floating-point values, when x has a value of 0.0 (zero), ilogb() returns the value
-INT_MAX.
ERRORS
No errors are returned. This function does not set errno.
RELATED INFORMATION
Functions: fp_class(3), isnan(3), logb(3).
STANDARDS CONFORMANCE
This function conforms to the XPG4 Version 2 specification.
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