HP-UX Reference (11i v1 05/09) - 3 Library Functions A-M (vol 6)

ilogb(3M) ilogb(3M)

NAME

ilogb() - returns an unbiased exponent

SYNOPSIS

#include <math.h>

int ilogb(double x);

DESCRIPTION

The ilogb() function returns the exponent part of x. Formally, the return value is the integral part of

log base r of |x| as a signed integral value, for nonzero x, where r is the radix of the machine’s ﬂoating

point arithmetic. The argument x is a double-precision ﬂoating-point value.

Note:

ilogb(x) is equivalent to (int)logb(

x) for all values of x except NaN, ±INFINITY, and zero.

The ISO/ANSI C committee has approved the

ilogb() function for inclusion in the C9X draft standard.

To use this function, compile either with the default

-Ae option or with the -Aa and -D_HPUX_SOURCE

options. Make sure your program includes <

math.h>. Link in the math library by specifying -lm on the

compiler or linker command line.

RETURN VALUE

If x is NaN,

ilogb() returns INT_MIN.

If x is ±INFINITY, ilogb() returns INT_MAX

If x is zero,

ilogb() returns INT_MIN.

ERRORS

No errors are deﬁned.